Development of a Carbon Carrier for Oligodynamically Active Silver Citation Harris, Franklin Stewart, Jr. (1941) Development of a Carbon Carrier for Oligodynamically Active Silver. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/pdy2-0v47. https://resolver.caltech.edu/CaltechTHESIS:02032025-231119947 Abstract No abstract. Item Type: Thesis (Dissertation (Ph.D.)) Subject Keywords: (Physics) Degree Grantor: California Institute of Technology Division: Physics, Mathematics and Astronomy Major Option: Physics Thesis Availability: Public (worldwide access) Research Advisor(s): Goetz, Alexander Thesis Committee: Unknown, Unknown Defense Date: 1 January 1941 Record Number: CaltechTHESIS:02032025-231119947 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:02032025-231119947 DOI: 10.7907/pdy2-0v47 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 16985 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 04 Feb 2025 22:37 Last Modified: 04 Feb 2025 23:08 Thesis Files PDF - Final Version See Usage Policy. 17MB Repository Staff Only: item control page

DEVELOPMENT OF A CARBON CARRIER FOR OLIGODYNAMICALLY ftCTIVE SILVER Thesis by J.i'ranklin Stewart Harris Jr. In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy California Institute of Technology Pasadena, California 1941 SIDfilJiARY A carbon carrier for silver bas been developed to act as a source of silver ions useful for disinfection in oligodynamic concentrations (0.05-1.0 parts per million). A certain type of carbon, consisting mostly of lampblack, was found to fulfill the necessary,conditions of electrical conductivity and high electrolytic adsorption. This material, in the form of small, hard cylinders, is impregnated with silver by soaking in a 10 per~ent silver nitrate solution for a few minutes. After air drying, the carbon is heated in a muffle furnace to reduce the silver to metallic form, finely dispersed throughout the body of the carrier. The carbon silver carrier is then given an anodic electrolytic treatment, charging with 90 coulombs per 1.6 gm. carrier at a cu~rent density of about 7 ma./cm. 2 for 30 minutes. After charging, the carrier is carefully rinsed in distilled water and air dried. Although the process by which the silver ions are emittea from the carrier is of an oxidation nature, the complete mechanism is not ' y~t entirely understood. The electrolytic treatment gives the carrier the property of emitting silver when immersed in water. The silver emission, which is germicidally ~ctive, declin~s exponentially with the time, giving approximately 5 mg. in 90 minutes, and is complete within a few hours. The prepared carrier is unaffected by heat even with a 1 hour exposure to 550° c., and retains its activity over periods of more than a year, whether ~Tapped in cellophane, paper, or sealed in dry air or vacuum. Acknowledgment The author is indebted: To Professo~ A. Goetz, Director of Research of the Bare Metals Institute, for suggesting this research, for many fertile ideas, and for his constant direction; To Dr. R. L. Tracy for generous and effective collaboration; To Drs. A. Dember and ·s. Kyropoulos for clarifying discussion; To Dr. D. Y. Chu for patient collaboration during the preliminary stages of this investigation; and To the National Carbon Company for preparation of carbon materials. TABLE OF CONTENTS summary. Acknowledgment. I. Introduction. 1 A. The oligodynamic action of metals. 1 B. Methods of activating silver for oligodynamic purposes. 2 II. Carriers for the oligodynarnic metal. 5 III. Determination of silver. 5 A. Methods available. 5 B. The rhodanine test. Procedure and precautions. 6 IV. Preparation and properties of the carbon silver carrier. A. The preparation. 9 9 1. Lampblack and the dependence on the type of carbon. 9 2. Introduction of silver into the carr~er. 15 a. Electrolytic. 15 b. Chemical. 15 c. Physical. 17 5. Reduction of silver salts in carbon. 20 4. Activation of the carbon silver carrier. 22 a. Heat. 22 b. Electrolytic. 22 (I). Charging conditions. 22 (II). Amount of silver in carrier during preparation and use.. 25 (III). Effects of electrolyte. 26 B. Physico-chemical properties of the prepared carrier. 30 1. Rate of silver emission. 50 2. Stability of emitted silver in sqlu,tion. 50 5. Stability and destruction of activity in the prepared carrier. 52 a. Time and storage conditions. 52 b. Action of chemicals. 35 c. Cathodic reduction with hydrogen 55 d. Heating. 53 v. Theoretical discussion. 55 VI. Conclusion. 58 Appendix. Bibliography. I. INTRODUCTION A. The 0ligodynamic Action of Metals. A writer on medical subjects in Sanskrit of 2000 B. C. said: 11 It is good to keep water in copper vessels, to expose it to the sunlight, and to filter it through charcoal. 11 (l) The Egyptians apparently used silver plates to cover open wounds to cause more rapid healing, (2) and Cyrus, on an expedition, stored his water in silver containers. (5) Nageli (4), however, made the first careful modern investigation of the effects of low concentrations of metals and their salts, and reported the growth-hindering and killing effect on algae. The word oligodynamic was coined by Ni:igeli to denote the ' power of a small number, thus an oligodynamic substance is on~ 11 effective in small quantities" (5) in disinfection. This may be d~fined to mean the range of concentrations below 1 milligram per liter. The literature covering the research in oligodynamics includes several hundred papers and scores of patents. Summaries of work with the various metals, and their applications under a wide range of conditions, with extensive bibliographies, are given by Saxl (6), Siebeneicher (7), Raadsveld (2), and Goetz, Tracy and Harris (8). Though disinfection of many liquids has been investigated, the principal use is in sanitizing water. The concentr~tion of silver necessary to disinfect water in two hours, contaminated with non-sporulating bacteria, is agreed (8), to be in the range 50-500 i/liter. (la-'=. 1 microgram) B. Methods of Activating Silver for 0ligodynamie Purposes. Many types of methods have been utilized to produce a sufficient 2 concentration of silver ions in the water to be disinfected. It is now generally agreed that the active agent is the silver ion, though the mechanism of the biological action is not understood. Since metallic silver is only soluble to about 25-55i/liter, even with long exposure to water (9) (10), it is necessary to activate the silver in some manner to get more silver ions available. Examples, taken from the patent literature, of different kinds of methods include: Heat silver salts or gels in oxidizing or reducing atmosphere (ll); a silver coated material subjected to 11 corroding" material such as ozone or·chlorine (12); two metals connected together with or without additional potential, one metal being more electropositive than hydrogen, the other less (15); electrolysis or current between silver or platinum electrodes through a sodium chloride solution (12); activation of a metallized carrier by making it anode (12); impregnating a filter by precipitating silver chloride, arranged so that the silver and chlorine ions meet in the filter (~4); reducing silver wnere it can be absorbed by suspensoids such as clay or subdivided carbon (15); coating a material with silver by reducing silver compounds (16); clinker macerated in silver nitrate,, the reaction forming silver hydroxide, then ~he clinker made into filters (17); zeolite and silver nitrate, using partial base exchange reactions and reactivation with sodium chloride (18); oxidizing silver to an oxide with-a permanganate (19); using hydrogen peroxide and silver (20); increasing the surface e:i-..--posed so that more silver will go into the liquid (21); using an electric current between silver electrodes in the liquid to be sterilized (22). On the last method, 11 Uniform distribution would seem to be the only advantage over adding silver nitrate. 11 (25) For other patents see (7)(9). II. CARRIERS FOR THE OLIGODYNAM-IC METAL Several types of carrier ma~erials have been tested. Examples of such materials tested are silica gel, nephri~e, charcoal and lampblack. In addition, three commercial products, used as sources of s:Uver, were tested, 11Katadyn 11 on ceramic beads and gravel, and 11 Syngasept, 11 which is a silver-,manganese dioxide on pumice carrier. The Katadyn beads, ~erhaps because they were old, were very poor sources of silver. The Katadyn gr.avel seemed to have an upper limit of a silver concentration of l~/cc. approximately, when used in a quantity of say, 50 gms. in 10 cc. for 1/2 hr., ,or in 200 cc. of distilled water for m~ny hours. off a total of 1.5 mg. Ag. 1.5 gm. in 200 cc. in 7 days gave Large quantities of the gravel have to be used or a long time since the emission is slow but lasts a long time. The long life was shown by changing the emission water many times and the silver concentration still reaching the equilibrium value. The Syngasept gave, in a typical test, l gm.in 5/2 hr. a total of -.015 gm. Ag emission in lO cc.; l gm. in 250 cc. in 12 hrs. gave a total of .0575 mg.; while 1.5 gm; in 200 cc. in 7 days gave a total of .9 mg. Nephrite was tried because it is an inert porous material. It was unsatisfactory because of the extremely small silver emission. Silica gel and charcoal bave good adsorptive properties (24)(25), and might be thought desirable on that account. If they were to be used merely as carriers for a solution of a silver salt this would be 4 satisfactory, but to be activated when the silver is in reduced form, a chemical treatment of some sort must be used (see patents). With silver alone, in reduced form, one test found :that .5 gm. silver crystals in 10 cc. water in 4 days gave off only .0059 mg. Ag, but, treated with hydrogen peroxide, in 1/2 hr. 2.5 ~- of silver had gone into solution. There is a material which not only has these adsorptive properties, but also is an electrical conductor, which makes available electrolytic processes to activate the silver. Attempts to c~~rge ot~er carriers than carbon, which is a conductor, were, of course, unsuccessful. A piece of charcoal had a resistance of 30 megohms compared to a piece of carbon (W5B) with 5 ohms. It follows from the above discussion that the twb properties which make carbon desirable for investigation are its adsorptive qualities and its electrical conductivity. 5 III. DETERMINATION OF SILVER A. Methods Available. Much of the early confusion in the oligodynamics of silver arose from the inability to detect or measure the amounts of silver giving the effect (2) There are now available a great many tests for silver which can measure the small amounts characteristic of oligodynamic activities. The following methods have been used by various workers: 1. A colorimetric test with .E_-dimethylaminobenzalrhodanine, with a sensitivity of 1 part in 5 x 106 , or 20 f/liter (Feigl (26), Kolthoff (27)); a modification of this test employing adsorption on a collodion membrane is sensitive to 1 part in 4 x 107 (Ettisch and Tamchyna (28)). The procedure developed at the Bureau of Standards gives a direct test in the range from 60 to 9000 i/liter (Schoonover (29)). 2. A colorimetric test with pure methylene blue reduced to the leuco-compound of sodium formaldehyde-sulfoxylate (Schumacher (50)). 5. A colorimetric method based on the formation of red silver chromate. It is suitable for determining 25 f of silver (Krainick (31)). 4. Potentiometric methods which are sensitive to about 1 part in 108 (Krause (32), Rfepelka and Taul (9), Rosenfeld (55)). 5. Afte~ concentrating in the water by suitable means, the silver is removed electrolytically from an alkaline bath and finally determined volumetrically with .001 N iodide solution, using rhodanine as an indicator (Egg (34)). 6. Nephelometric methods (Kfepelka and Taul (9), Kul 1 shii and 6 W1Utilino (55), and Hahn (56)). The method of Hahn is a nephelo- metric measurement based on a redo~ reaction using mercuric chloride, and sodium hypophosphite, and measures down to 1 l/liter. 7. Haber's method of adsorption of the silver on PbS and determining the amount by fire assay (Freundlich and Sollner (10)). For references to other methods see (2~). It may cre noted that the potentiometric methods measure the silver ion concentration; and the other methods determine the total silver present. 't'he rhodanine test was selected because of its simplicity, accuracy and rapid manipulation for determining small concentration~ of silver in water. (29) B. The Bhodanine Test. Procedure and Precautions. As a quant:i:tative test for silver, the cuinrimetr±c determination with .:e.-dimethylaminobenzalrhodanine developed by Feigl(26)(Cf. (27)) was used. The procedure of Schoonover (29) was follovred with slight modifications. The procedure is as follows: To a 9.5 cc. sample of the unknown, whose silver content is to be determined, add .5 cc. of 4 N HNO~ to 5 make a total volume of 10 cc. After shaking, .6cc. of saturated alcoholic solution of _:e-dimethylaminobenzalrhodanine is added and the solution again shaken. After half an hour comparisoµ is made with standards of knovm silver content, made by dilution frore a stock silver nitrate solution. Enough ,E-dimethylaminobenzalrhodanine is dissolved in 95 percent 7 ethyl, 5 percent methyl alcohol to make a saturated solution (0.02 percent). It was found that using .6 cc. instead of .3 cc. rhodanine, there was less of the 9ccasional change from the normal pink or red color to an off-color (see below). The amount of rhodanine used places a limit on the useful range which can be measured, tlms, if. the concentration was more t.~an about 1.4 fee. the exact amount was not easy.to estimate so that in practice the unknov-m was diluted until a comparison could be made in the range less than 1.4 f/cc. Though a colorimeter was used at first, this was later abandoned for direct visual comparison, to save time1 and since an accuracy of about 5 percent was sufficient. For accu;rate comparisons, fresh standards were made each day, since in about two days the color may give an apparent smaller concentration of about 10 percent, or more, the higher standards tend to flocculate into a precipitate and the lower standards to fade.· Precautions. If the acid is not added, an orange color develops when the rhodanine is added, with or without the presence of silver. If the acid is added later the orange color weakens and becomes yellow, hence the importance of the right order in adding the reagents. If twice as much acid is added, the apparent concentration of silver is about ba.lf the real amount. With a concentration of 1 {fee. Ag, the color is not appreciably changed by concentrations of H so4 smaller than 0.1 percent. 2 . this concentration of H2so4 the color is decreased. Above Schoonover (29) reported that a very small amount of H2so increases the depth of the 4 rhodanine color. 8 With a concentration of of 1 Y/cc. Ag the color is not appreciably changed by a 01- concentration smaller than 0.6 i/cc., whether from HCl or NaCl. Above this concentration Cl- decreases the color. Tap water had no color when tested. Copper(Cuso4 ), mercury (Hgcl 2 ), and lead (Pb(C 2H5o2 )2) in a concentration of 1 y'cc. gave no color, except the mercury with a very faint pink too weak to be measurable. With manganese nitrate 20 'f/cc. Mn did not affect the test for 1 f/cc Ag, nor did al percent solution interfere though it seemed to be lighter in color. A gold 1 '(/cc. shows the same color as . 3 1cc. Ag. Soaking 2 mm length of fine copper wire for 2 hours in a 1 o/'cc. Ag solution reduced the concentration of Ag in a solution by ?O percent. Pyrex test tubes were used and after washing with tap water, they were cleaned with cone. sulfuric acid-potassium dichromate cleaning solution, rinsed with water and boiled in distilled water. Moistureproof cellophane was used to cover the corks. unsatisfactory. Rubber stoppers were These precautions, with the change in the quantity of rhodanine practically eliminated an occasional capricious change to an off-color orange or yellow, which appearing on standing, varying from a half-hour to a day. The cause for this color change was never isoiated, but the procedure above seemed to almost eliminate it. Pyrex tubes were recommended (29), but soft glass tubes, given the same cleaning treatment were also found to be satisfactory. also cleaned with chromic acid solution. The pipettes were The carbon samples v1ere· first suspended in the test tubes containing 10 cc. distilled water by an enameled copper wire, but it wa~ discovered that when the enamel had been scrapped off, exposing a small area of bare copr,er, the copper replaced the silver in a concentrated silver solution (100 ~/cc.) form a small silver crystal at the exposed point. sufficiently to Silk threads were then used. 9 IV. PREPARATI0N P~1D PROPERTIES OF THE CARBON SILVER CARRIER A. The Preparation. Tl}e .. standard treatment developed employed a carbon (F5B) with high lampblack content, low temperature final bake in manufacturing and made wettable. This carbon is soaked in a hot 10 percent silver nitrate solution for 10 minutes, allowed to air dry on a paper towel, and then to redµce the silver is heated in·a covered crucible in a muffle furnace for one hour ·at 0,75° C. curves of muffle furnace.) (See Appendix for calibration The carbon is made anode in a very dilute sulfuric acid solution (.Ol8 1 N) and a current of 50 milliamperes (ma.) per carbon is passed through the electrolytic cell for 50 minutes. (See Appendix for sketch of carbon holder.) After treatment the carbon is rinsed in distilled water to remove ~~e electrolyte, etc., and allowed to air dry before use. "standard carbons," Carbons so prepared will be referred to as and show less tban 10 percent variation between individuals. "The development of this pro9edure and the conditions affecting the amount of silver emitted from this prepared carrier are discussed below. l. Lampblack and the Dependence on the Type bf Carbon. Pmorphous carbon is considered by most workers to have the same type of structure as graphite, except that the crystal units are smaller. (57) .As expressed cy Thiele (58): 11 Iritermediate members of this series (nf~forms lying between crystalline graphite at one end and amorphous carbon at the other) comprise all the transition forms of crystalline graphite, namely, amorphous graphite, graphitite, 10 graphitoid, retort carbon, etc., up to amorphous soot carbon: further, no sharply defined boundaries exist in this series between graphite end amorphous carbon; and X-ray diagrams shovr that even amorphous carbon still possesses some graphitic structure. 11 (see also (39) (40).) This means that there are just the two crystalline forms of carbon--graphite and diamond--though Ruff (41) says that amorphous carbon forms a third. The ty-pes of carbon tested (Table I) were made with varying amounts of lampblack '(amorphous carbon) and coke. The carrier properties of the carbon improving with the increased amount of lampblack. These carbons also test differences in the manufacturing process (42), including the temperature of final baking, effect of boric acid, skin usually on carbons from extrusion die, .wettability, addition of silver in the carbon dough, and. a wide range of lampblackcoke content from almost pure petroleum coke to a very high lampblack content carbon, with just enough coke to serve as a binder. The carbons as indicated in the composition below are not pure carbon (45) (44) (45). The composition of W5B as given by the National Carbon Company is as follows: It is 99.8-99.9 percent carbon. The total impurities amount to .08-.17 percent, all water insoluble. Of the impurities the proportion is: Si0 2 50-6 0 percent Iron and Aluminium Oxides, Fe 2o6 and A1 o 2 5 Calcium Oxide Cao 25-40 percent Silica Mn, B, Mg 1 percent, approx. each a trace. The ash of this carbon as obtained by heating at 6000 in the muffle furnace amounts to 1.0-1.5 mg. 11 TABLE I CARBON TYPES, THEIR DESIGNATION AND COMPOSITION Designation Size hole j diam. x lengtb. 61 LCl 11 W4B WBB W2BC yes yes yes yes yes W2BD yes W5B no NlA NlB V.UB2 yes yes yes WBB2 yes W5B6 no no Wl.A. , WlB 81 SWl SAWl no no W4B no W4BS2 no W4BS5 no W4BS4 no W4BS2A no W4BS5A no 1J.i4BS4A no W4BS5 no W4BS6 no W4BS7 no W4BS8 no 8 mm. 8 mm 8 rnrn 9 mm 9 mm 8 mm 8 mm 8 mm 111 1 11 Composition high coke content 2 parts coke, 1 part lamublack 1 11 high lampblack 1 11 highest lampblack content:, low temp. bake 1 11 • next II II II II 11 1 high u high If 11 1 11 sam.e as WlA low II 11 1 lower lampblack, contains n boric acid 11 same as W2BC but no boric 11 acid 8 mm 1 11 purest petroleum coke available 11 n same as Cl but low in sulfur 11 8 mm 1 same as WlA but nonvrettable 1 11 same as rrrlB bui;, nonwettable 8 mm 8 mm 111 same as WlB but outer skin, produced by the flow tb.e the material through the extrusion die, removed by grinding. Centerless ground stock 9 mm 111 same as V15B. Baked at 1000° (factory duplicate of previous laboratory lot) 1 11 same as W5B except baked at 6000 7 mm 11/8 11 impregnated at factory with ca~ .45 percent 7/16 11 Ag, about 15 mg. ratio of silver of others are with Sl taken as 1.25 11/8 11 same as Sl but wettable 7/16 11 7/1611 11/8 11 same as 81 but "factory activated" 1 11 high lampblack 7/1611 8.75 5/811 19/16 11 7x silver of Sl; taking '31 as 1. ~ 5 11 11 5/811 12.50 11/8 11 lOx ratio ll/8 11 l5x II n 18. 75 5/8 11 11 19/1611 "factory kctd.va,tefl,lt- W4BS2 8.75 5/8 11 11/811 W4BS5 12.50 5/811 11 18.75 11/8 11 W4BS4 5/8 11 111 ?.00 8 mm 111 .4.00 8 mm 111 6.00 8 mm 111 8 mm 8.00 8 mm 1 11 Lampblack (powder) itself can be used as a carrier for the silver. A lampblack powder, .5 gm., charged, by holding the powder against a silver wire with a cotton sack, at 55 ma. for 10 mins. gave .24 mg. Ag in one case and .96 mg. in another sample, as against a control of .006 mg. impregnated and reduced but not electrolytic charge. This powder is so fine it is difficult to handle. 6.0 mg. Ag were given off by a 5 gm. weight of calcined lampblack given "standard treatment. 11 The calcined lampblack is a lampblack whtch has been heated with some pitch or tar and then ground to 100-150 mesh. The porosity and wettability of the carbons are important. Carbons given a treatment at the time of maki~g to have them wettable (designated by w, non-wettable by N, or no designation) were found to reduce·the variation between individual carbons given the same treatment. The porosity measurements do not necessarily give an adeauate idea of the permeability or adsorption capacity (46) of any variety of carbon. The kind of pores are important; the pores must be intercommun- icating (47) to 0e efficient, the larger pore size (48) (49) permits more electrolytic action (50) and more oxygen adsorption (51). Oxidation increases the pore size (5~~- Table II shows the amounts of silver which different carbons will absorb when soaked in the same silver nitrate solution and heated at 600° to ash. Types 11, LCl and Cl could not have the other material from the coke fraction removed even at soo 0 , though ' there is a high ash, there is actually no more silver in them, but probably less, since.their silver emission of those with much coke (C) is about 1/10 that of LL It will be noticed from Table III that those carbons which have a high emission rate absorbed 2 to 5 times more silver. 13 TABLE II -.. VARIOUS- CARBONS Af\1D THE Al10UWT OF SILVF!R ABSORBED Type Center Hole • Cl Weight Total Ash no 1.14 gm. LCl no 1.34 Ll no 1.12 W5B no 1.76 W3B6 no 1.27 W5B yes 1.63 W2BC yes 1.40 W1B2 yes 1.19 1'\iJ.A yes 1.55 NlB yes 1.26 NlA yes 1.26 WlB,._ yes 1.20 W4B yes 1.11 156.8 mg. '159.3 213.0 195.0 63.4 65.4 37.0 38.9 36.1 52.7 51.l 58.1 20.8 19.0 25.8 lost • 20.0 22.5 25.5 25.9 25.2 22.. 7 55.4 35.7 64.0 49.4 • 1 - TABLE III SILVE..B. EMISSION FROM C.ARB01:S WITH SAME PREPARATION Type W2BC WlA WlB2 1111A W4B W2BC WlB NlB W5B W3B Emission in 90 minutes 2.8 mg. 2.5 4.0 5.6 6.9 4.7 9.5 5.4 4.6 9.0 -2.9 mg. 2.2 . 4.1 3.8 8.6 4.8 9.5 4.0 4.5 12.0 111 m~ 10 9 .. H r ;_ 8 ~ : -t= I:": 1:---i-= ~f .. f 1f§B 'fl ft f. I ··t-i tl _,., 5 ~ etc:!". ~ r- " !~ .m :8 ++ .fl H I!:, fi :m ~ ' :: i k + . . .. +JL!tl ct, t ; llll! :\1 E1c: +~ ;-~Pf!tI fi1~ .. ~ 1,5 2,5 -• 2 a Tu ';tl:t Ctr : ~± H '. ta :it :.l: f 3 -~ :11+1 n: ·•• - 7 9 10 t:r ·• == I~:t: :t !$ :l..;.t :t ltt:J::t ~ n!rfrw .,I F luffi '=t Hf :t: lt!:H t"!.ffi }!1 j+ Jf:f-fj : '§f·, L. rri (:.ii ~-+ ~ I~ , -- _J- fill: Il:E H ' ~ $. :::tl :1 R= I+ Utt 6 l i:l t:1·:-t ~H:itffl . ·H • ·. w+ cf: ·i : 1 lf f'. 4 5 6 8 1,5 2 2,5 3 4 5 6 7 8 9 10 14 ,~n extensive etudv of the tempers_t1.rre of 'T E: heatim . oefore trPa,t ment and the te mper a ture of r ec_ uction of th e silve r nitr•tte a s a function of the emount of silver erni tted i n wa.ter found a v~.rietion ~·ith diffe rent cr:rbons. :,,:os t of th e c✓. Tbon :c he,d t hsir emi s s ion incre ased by ,)r eh er,t ing , if t.1:e ,r 1ner F: not 1~·r ch e:3 t ed t hen "'- higher reduction t er.r,ier e ture w1:.,_s n6wrntP,2:eous . This t erii;Je ratun: e ffe ct is probably rel a t ed to increas ing the oore s ize. :toB , the 1 carb on ad o ted , ha c_ but e. sm8.ll temoer r, ture ef f ect of t h i s k ind . Ti::.ble III c ive s the emis s ion amo1mts for V!".r j ous c1:1-rb ems ,,r,~h ee_ ted at soo 0 for l hr. Rnd rec ucecl <>_t 500° for l h.r. I n fi q . 1 the emis sion curves e,re given, thr, 1:un01mt viven in h"lf-ho1Jr rer iod_~~ -olotted HP,'Ains t the time . L5 fl.'?. Introcuction of ~ilvF,r into the Ca rrier. The silver c&n be introduced into tne carrier o--- electrolvtic, chemical and vhysical rnetl1ods. The electrolytic cieposits silvsr on the Cctthode, but since only on the exterior, this i2 similar to usinp a silver sheet. The cnernical method coPsists of so2,King the carrier in a solution of a silver se.l t. The physice.l method is by mi:xinp: the c~irrier in pov.rder form 'tri.th silver or a silver s,.:. l t. Chemical :,lethod. Silver nitrate, wit.1-J. its hj_gh solubility, i-18.s been found to be the most satisf1cctory silver salt to introduce into the carrier bv so.s.king. Silver nitra.te is the usuel comrnerci11l form of silver. A high solubility is necessary since a carbon absorbs the order of l cc. of solution and with the less soluble salts such P,s silver c:irbonate, oxide and sulfate, not enou~h silver could oe introduced. into the carbon to be efficient. Since the amount of silver in the carbon de- termi.nes the amount wi:ich can be obtained 11.fter tre8 tment, the lowsolubility silver salts v1ere undesirrJble, as confirmed by tec",ts, because of the low A.mounts of total silver introciuced into tile carbon. The amount of silver which is sm1ked into ti10 carbon seems to be a linear function of the concentr,qtion of the salt (fig. r:). The resulting activity when 0;ivcn a. usual charge of 5 1) ma. for 60 winutes is also shown, as well as the emission from an 1mreduced thouG,.h charged carbon, s.nd the amount of residue, e,fter sosking, from both reduced. e.nd unreduced carbons vrhich 1'1:tve been cn-'3.rg:ed. The a.mount of emission denends on the charg i11g time and current. \\hen 10 ma. c.r.arging current 1:ier carbon for 10 r;1inutes w.s.s used, study of the concentr2tion of sj lver P,s nitrate and silver emission found, this lin8ar relatton wac" roui-:hly true for 0.1, 1.0, and 5.0 percent, but that 10.0 to 40.0 ·oercent emission were about t he s ,:i.me as 5 oercent solution. There is nrobEJblv e.n optimum 16 chRrginf, cond.i tion for e2ch sj_lver ni tratr, concentr::dion. 'i hus if s. nigh chr3,rge is given for a long tj1lle li t ·sle s i lver viil.L be le f t for emission and no increase in emis :c ion r:1te or a mount is obtained. The 51) ma.• for 0 1) mins. c)~g_rge is based on u. 10 t:iP-rCf., nt s olution. It was noticed t:-iat the silver nitrate solt;tion tencLs to become more concentr2.ted ,,i th use; a 10 Dercent solution ,·.'hich through use had been reduced to a frn.ction of its original volume beca me 55 oercent. The ce.rbom: impref!'nc·ted ,.,.i t.h ti:->..is ,J1., rticubr solution of silver nitrate received increasing amounts of ~::ilver as the volume of the im:or8,m,;ting solution decreased. This we.s confirmed by the emission and the silver residue after em:j..s e:'.ion, a nd 2.ccounts for some of the variation of tests m2.de in that ·oeriod. It 'Fa s found tha t more silver ni tre.te oenetrated into the c1irbon when the c a.rbons were soaked in a hot solution and t his :,ractice was 8.ci.01)ted. ,,; rhen the carbons ::i. re immersed in hot silver nitr~1te solution it is t·:no1r,rn thP.t ·oart of t.he silver nitru te is reduced i::Jy the carDOn to metaLLic silver, and part is a dsorbed as oxide and pert P,s ni tr;;te (62) (63) (64) (65) (57). Further evidence is the smell Pt the time of immersion; a s meLL like t ent of coke ourning in B.n o oen grill. Probabl v not a lfire:e oi2rcent.s.?"e is reduced since -r)ra.ctica.lly ,,. 11 the silver wi l l come out ,,:hen the c ,i rbon is so,J.k eo ir.. c istil:i_f,ci 1r ater, see fig. ~. ;;•ith the ni'.!ht-cr coke containing c;:;rbons t :,,crs is ,; fine stYcr kli.ng surf?,ce of silver cr~vs tal s on the outer c::i.rb on s urfnce '11en 01 the carrier is r emoveci. from tne silver nitr0.te solution, t ilE.y '. tre als o visible immediately after iml!lersion (66). t compo.rison test of Feigl 1 ~, mang:anese method 1 53) anc:. the electrolytic method of activ.:-, t ion 2,nd silver nitrr, te giwe the results shovrn in Table IV. four 11 c<::.rbons ·ere s o2ked in 10 uercent silver 17 nitra te and four s opJq=>d (lJ mins.) in Fe i,~1 1,: mmmer in :_i. 4 0 cc. solution (2-.64 gm . silvEr ni t:r-,3_ te r, nd 4 cc. of 50 pPr ce nt m;;;.ngane.~e nitra.te solution, mul.e up to 4:) cc.) 'l'i,7 0 s::;rnpl es , l. B vn:. E:0ch of silicr, gel were a lso so8.ked in Feivl's solution. Two of the silver ni trc1.te tre a ted, two of t he F'eie-1 r.nd one s.?r.,ple of s ilica gel vrere sM.ked 10 n ins. in hot l 't1 " a OP, then d ried. The other sampl es were heated to 600° for l hr. and che_rr.ed electrolvtic2.llY. 'I'he silver nitrate c,,.rbons treeted vri th Nt.0H gnve an off-color rhodanii1e test. Phvsical. The mixing- of si:iver vd.th its c2.rrier may oe d one in severr: l ways. Mixtures of silver powder or s i .1 ver Rci.lts wit.Ii. va rious oxi ces of coba lt, corrp er or rnanganese wer f. not efficient, litt,le , if 1=rny more, <At silver went into solution tbm would be exoecteci ,, it ,f.,_ t r1e B.cc:ed foreign S-':1.l t. Ca.rbons with w,.rying mnounts of silver rnixe6 j_n tne carb::in oougr: during the -or o cess of manufacture (see Table I where S means silv,or .<:td.c?ed durinF. mH nuf?.cture). 'I'he emount of silver -3.c.cec.; r- ·:ngE:·d from about 15 rng . De r cc1rbon to 34 1) ( l n.r ger d ze) . The amo unt of silver emitted increa sed with the silver content of th e ca r·oon, tr1-s ···as 1 true whether the cn.rriers 1"erE, s o ~'.ked in wi:i.tr=::r As the-.r c.' ,.mn from the factory, or whether they v1ere ~iven an electrolytic c.ctivntion, the latter f; ivinF .sn ewission of ? to :) tii.-w:s more si lver. Ev en though t l~ey h~d 18.I'ge a.mounts of silver e lre:, d'.' , the s ilver n:i.tra te treatment 12:ave a still greater ~cctivity. '.3incs the ruriount of silver Eldcec3 in the dough he.d to be four times t hP..t fJiced in the usmJl silve2' ni tr8.te im-ore,a,n c:;tion thi s s cheme wa c; a.bano oned . Silver oxicie i s not v er s oluble U:o mg . / lite r) but \ hen cL'.<; olved 11 18 :i.n a concfm.trater.l. s olution of a.1-r1,11 oni 1:1 , lar2"er - u,mtities c e n be inrnrer-nr..ted into the C"!T i)on, or so0.ked onto t he c arbon nowc.e r. This may b e then heated ( 54) to drive off the amrroni::i. and vr::i. ter, .s.t around locl, aoparently forming in tr2ns i tion fulminr-tinr: silver ( 55). If t .nen hea ted to still higher temnera.tures r.i ore ,;il.ver is availab Le in the 10 cc. test tubes of emis si on than ·.,,t lo1,1 er temuerature he2, tin£", and more t han the u sual a mount of s ilver oxide to be expected in 10 cc. (. ? 2: m) . The tote.l e.mou.."11.t of silver emitted was indeoendent of the volume of emis ~don. For d,:a t-s. on /1g, .. :, 0 see Table V • The e rt·ect obtaine d bv rr.ixing 50 n•g . silver sulf· 1te v1ith b em . of c::i.lcined carbon and heA ting t o various te:n ner.::, ture: s rna y be ~-ee ·n i n fi g . 3. Only about one-sixth of the amour-t of silv,:r pr csent in t ne water in 36 hr s . was to be found when te s t ed 11.t'ter t v; o h01Jrs . :':3ilvEr sulfate nov1c.er d oes not r; is,, olve raoidlv in wp,tcr. /I small amount of silver, lytica.LLy ch8rge<i. . ? 4 to . 'ci 7 m,Q;. v,as ob tainec'. bv mixing This se ms to ind :i.c-· ,ted e it rer t ~r.t the c nanrec: 0 C"l.r 'o on ce.n oxid tze tne silver ((56 ), ser, V), or t r.ri.t a loca l e l e mer,t n1aY b e formed betv·een the n:{rticles of s ilve r end .113.iooblo cK 8.ole to send the si1vF;r into sol 1.Jtion ( C' f. fi g . 11, (5 7) ( ::it, ) (5::1 ) (t,)) (0) . Since 8. silver vrire v'e.s u s ed. as conta ctircg e l ectrooe ,, i th the l ampble.c1c, some of the silver may be from the electroce , r,, moved h.r the usual nrocess when silver i s i:m 8nocie in rm electrolytic c e ll. Thiele a nd Tr,olf (61) r en ortecJ that . 5 iliP: CE:.rbon mixec v· :i th 1 Fm. silve r pov'c'ier n~d enough loc"' l ele!uent '• ction t o i ncre •? se the ste rj 1.e ✓.on e Q on +I :n ~+.' t:_2 J i:;::; +- j l :fR ill ;+ i-;+ ,-ti -'+•• -:::::.1 m r:r . . :q .fl ] 1 J + ".;l µ..;., ~·+. "T • t..u ri:J Fl' ~ :':. : ; : tt;:;: .:" ~ -:.::1 -j·· .• :.. r:: t:E.. ,:-/" t_ ':: ·. '-H - ~-~+ . °';ft::+'' f'.ImTJ 11:rr.nj_"1~:f:li1 :•· It 4 .,. H·---• i ll :Jlj,:;:;.:t :I .•'- •-t:=-+-:-~ . :.: • rn=r :fu H---t ........-. - ~ ~i. ;:;) ~: .: : T, lfi r.w::+1 - •..-. (!"'1-t"t ~; ➔ ,:·.:::i ~ : •·t+H--t~ ':;.ffllt ::j i+I i J • : • ~T:' • 1.: :. till ,-~H:t-1 •~. :J d ... l·r!_t+ :- : :t±t'• .i., • .,. ~ri + :: •r::TrrL B ~:: :i~EB:l : ---i -H •• H-H++:::±1-<---:•t-+nfil:li cl l lf':1:,, :r" ::-r-:1~:: . :J .. 1 r ~F J:l~ ~:-:. Lr .n. TC '.cii: E:E ,;h IE Jr:: H:~ t-if fil1 '.: :.. ~ E :;: i:. ,+3 (1 q_ :r -L;'. ,.: t·· ;:;." •:__;...: :u.: . ..,, 1+· '?: :; ••• : ➔ I -i-IT.-1 ::;;t • :.J:l •· ,.;.+k. :i:;j l :..;· :I ' ts-r ~ r ,1 • .... 1;;+ •+• 1' j. : - '.1 , ..µi+..;.1..:-1 J ·:~i- !. i •• 11 :i ·.:...t..-.· ··•- • :;.. t-.;.. ' f· tt±:L.:.... .. ~ Hlll ~ !.i ~ , 11:; ,.J:_:.. Fl ~~: :::J '.f'1-I ··-r- 'M t-.-.:t • ~ : !:!E :; :; ri1,; rJ=;iii;· ill -''➔ :1 rrr~· ~~-!;•· - -,~h,Tj_.uf d_ '.ii -7 i:i-::1 T·'· • l ;:.: I.. :;·, fB 11+ ·:--1 i§ 'I'.ABL ~ IV Carr ier Imor env, tion Activa t ion E:1:! i ::-:~::ion i n :~:_/';-: .n r • csrbon 'Z 1 tJ • L.,. ce.rb on lfa OH car b on electr olvtic c':l.r bon ~Hic 0 • gel (a) '1.'emPerr;.ture 'T'ime of He:.1 t i ng no ~-1cd, :ition°,l :50 1) 4 h.rs . l hr . 7 . 18 ~~ . b 600 ?() • ?<') ro 7 ::iY) 4 • Dt.J '~,:: 4i'.}) 1 l 1 1 445 1 SQQ 1 CC\ Z,50 ~) 50 c,50 4-()0 1 /~ 1,. ,._ ~A ~A r::4 4() Lj/)() 70 4 ')() ~I 15 0 ~~4() 35-5 (b) Time of 0 '.rnis s ion Yi!1 isc:j_on ,·· C .t' {, f , ~ ~- ?? 2i!. ,: r_ min . ?.4 24 hr s . ?4 ' ·''/. .6 . l,j 1.1 2. 0 ~ . 1J • 86 . 7 D '.{ - 4 . ;-) 1. 2 4.2 1. 8 4.0 4:. ~1.6 ;,_; . ~ 4.4 . ?? ' ~~) . 6 A. '.5. Reriuction of Silver Sal ts in Carbon. Silver ,:,21 ts c::m oe deconr-:osed by hen t.in ~r to w ,rious tPrnne r ,: tuJ'e s , silver nitr2.te (444 0) end silver sulfa.te (l:JS5°). The decom pocc:ition is a function of sever el va riables, incluo. inp- t ne tir-!e , oe ine ,"i th a more rapid rate e.~1 the tem :,er•·ture incrrc:r ses . It rn ~r-ht be slrnoo.c;ef. th::-it thes e s ;:;1 ts will be decomnosed at t ·;e s i;me tem ·, E;r 1ture ,,:0.en they 0 B.re in the caroon, or E.t least in some wh 0,t the sar.-:e r a n ~e . !~ctuelly, they are all reduced e.t a.bout the some tempera ture, e.l1o,ning for reRction r n.tes. Caroon ha.s a reducinp; -:1.ction bt t he temnern. ture it begins to oxidi ze (68 ). "i.lver o:x.ide is not re ouced until t hi"' n oin t (6 ;:J ), and silver sulfa te is likewise reduced (70), ev en Nhen only mi xed mechanichLLY with C!'c.lcinE1.i. c1:, rbon, fir-. :3 . The r o te is .c:,.l ower in the lstter CB.se 2.ince the contf:,ct between CF.•rbon ,,_nc, silver suJ.f,,te ir, not very gooo.. T},e ?Oint s ,,.re for 1 rir . :n8'.. tin F R.nd for l::i mins. :::ie e 8 lso DJ 13. Tne c~rbon (ii' {1b ) is cor:role tel-,r ox:i_Li,,ec to c:i. bout ::-._ l.0-1.S mr'. . ash --Oy heating to 60J O for 1 :-'. hrs or les cc , tds i s not the C-'."'se , ho,:ever, wi t n carbons cont; ininr,i: l a r2"e a.nnunt s of co k· e. In 60 hr2. (' 1ct 46') a. vr:53 ha d oxi r3 i7 ed to 5 mg . The re duction temoer a ture of the s ilver nitr~te "':-,en ne,, te c. for 1 hr. oid not sei:;•m to aff"'ect the 8mount of s :ilvor l~•t•~r e ,5 tteo, v-ith tern,:i E:ratures tuc.ied above 4?0°, with other lower-le.moblr,.ck content carbons, the nreferred re duction temper ature vm.s h~ rsher. The formP-tion of silver c <irbke is not to be e xpectE-d. (41) (71) Th.e reduced silver is very finely c•ispersed throughout the Cf:lrbon, there is no O!)tical difference bPtween t n.e cPnter and bottom c2rbons in fig. 4, the center is 11:ithou.t silver , the lower c ,rbon '"i th. :F'ig. 5 sha v;s a silver skeleton or co it of mail obti i ned by burnitA'. off the 0 0 a ca.r bon at 600° vvhich 1 ,:.2.ves the silver in the s~.me sha.iie a1, the C8.rbon, even to the fluting in the center hole. Fig·~, . 6 a m ' 7 show the surface of t '.1e co t of mnil 2, no. t hf: smalJn ,:,~,,: o~ the crvstn.ls b roken from t-11.e silver s tructure . Fi.Es. 4, 5 , 6, 'l ,1 re from nhoto.-rran hs ov Profes~or Goetz. Al th ouEh uncier some conditions some of the ce r iJon um tle oxidized r:.t ri::,la tivel:v low temperature s (7~), anu: oegins slowly Pt low tem;'.• erat. 1Jres, lo"'er tam are import'1.nt in such conci itions a.s nre used to reduce silver se.l ts, the oxida tion becoi"e" r o.oid enough to become imc)ortant in ti1e range 400-450° (fi"' . 10) (64) (:'.5 7). If the ce.rbon is reduced a t 60D0 for 1 hr. there :is no cetecbble hmount of silver which will be emitted from t11e c~.rrier in a halfhour, but At temner , tur<os in the range 40D-50:) 0 t•1er e i:~ e.bout .1 me . v:1-' 5.c ":-: can come out on s va.idn;:.' ::.n W8.ter. Cg- . 4 . ,)9 c·roon : untre•<tf'C, hole , (u_.uern cut in tv·o (:c1iacle) ; 1t 11 rerucec c::i Lv,=;r (lo•""r) . 1 . ;: ; r· "'"nj ic,,.tion . f·,.,. . ;, . 0 ilver sk"P.lFton from ashine:,B imnre.an,- ter' C"'rb<n. i:; . ~ rr:3.i, i.fic ti•)n. fig . 6 . ~urfGce of silver skeleton illuminBted by reflected light qno dr.rk fielc. . 70 11n.€_;nific,~tion . 7. -~·ter~ 0 1 r om bro''en .,· 1 vrr 9r,=,lPton illurr-in-~tc:.d oy reflEccter J.i ·t • r.a. "fr'{ fiPl • . 14') rr"' r.ni fi cetim . r · i:r . f.1. • 4 • ..Activa t ion of t he Ca r bon Pilver Car rier. TTe/,.t. i:t we. s found t hat t he ca rbon silver ca r rier c2_n be a cti va t ed by h ea t when t he method of silv er oxide i n ammonic. i s u :,.ed to get the si1ver into U1e ca r rier , se E T1-cble V end fi g . 9 • .c·ith silver ni tr'?, te the solubilit y is s o high t l:X'. t t he amount of silve r impr ep;n a ted into t he ca r bon makes such an ~ctivation rmlike ly since ·or a ctic9.l ly all t he silver nitra t e sec~ ms to come out a gain vrhen t he c a rr ier is s oaked i n vmter without first r ed ucing t he silve r (fig: . 9 ) . Fi t h r el e.. tively insolubl e s?.1 t s su c h as s i l ver c ar bone t e nnd s ulfr,.t e the e ffect is not certa in, though some de t a se em to ind icate a maximum P,t about 350° j u s t before t he r e ducing a cti on og t i>e c:,rbon s t a rts a t ab out 400° . The K:➔.tad:vn beads seemed to be somevihe.t im pr oved by heatinf . Efforts to activa t e the reduced ca~b on s i l ve r by prolonged heatin g in ca rbon d iox ide a t mos phere or b v cooling from r ed he8 t in en oxygen a t mos phere were tm su cc essful. The maximum s ilver from tre o:xye-en tre e.trnent v~as 3 . 5 garnr.a . Rlectrolytic. 1. Char /!ing Cond itions . Ry ma king the carbon carrier t !'.le anode in a n el ectricP,.U .y cond uct i ng solution ana a ·pplying a potentia l mor 2 t rnn the ctecom~Josi tion potentia l of ll'rater a t El.bout 1.7 volt s (Tf:, ) (or with ce.r b on ele ctroctes 8.bout 1.6 volts (74 ) (74a) ) oxv.;;en i s usualJ.v evolved a t t be anod e, and vari ous s orts of oxidc,t ion nro cess e ~; t ake pl a ce (75) . To fi nd out t :ne bes t current de n sit y P.nd t im ro for t his ele ctrolytic tre8.tment of th e c11rbons •?. number of studies wer e rnacie . Ta ble VI s t>o•,•;s the r esult s with 1;1:~B using 8.bout . 01 8 N. s ulf ur i c a cid as e l e ctrol y te, each point be ing t he averag e of t wo ca rbor!s . The silver re s idue Time ? .5 Li. Current i n mr.:i. • ::ier csrbon 81) 4() 10 16() 20 5 min. 4:J() 1 . 0 mr! 5 10 1. 5 r-0 . 76 ( 57 . ) 4n 1. 5 ~.? (5n.l) ( 4.:., . :~ ) 7.1 1. 0 :. :, . 7 5.~ 5. J lf") . 8 ~. b .3 . ·)'? 6 . 8 10 . 11 . ( 4 ... . 5 ) ( :. , .~: . 2) ( ?i0 . 6 ) l !: . t~ 7. 9.8 8.4 -:z,: ( t)() .1 ) 8() ~➔ . 7 7.8 (12 .7) 6.8 .:, 7?.0 ~1 . 6 /\ f! ~J.6 .s. :,; fl5. CJ ) (l. ?,) Carbon f,_g Tmor ApnDt ed Ch'3.r /J.'e Loss After Cb,r g in2· E:,, i ss ion i~.E- sic.ue v:r:·m 59. ~ AgNO 33 . 7 •;43 "•'43_c:2 W4B:-,3 1f"4:3:°'4 25 ..s 1~ . ? l ?~). ~) A~;tJo::~ 161.l mfg-. 6 4~l . 6 T,.7 L • "l. 5~i . :i ?? . 2 4.1 158 . 9 24~'. .6 II 40 • .:5 l 5tj .9 197.1 31 8 . ~ II 28 . ~; ?90 . 5 . ~:1 14 . 3 2i:l7 .:1 1 'Pll8T}i' 16. 6 U?. 7 VJTI Ele ctroly te P'-1 of ·: 9, ter in 1 1) cc Fmi s :0don Tube .s .o m.s: . Fv ~-. 7 °'olubili ty in 10 cc. .0.:_11 t 39 . 4 nw . 4. 5 :,; • 7-() .1 1420 0 .8 4 • 7-'fi • t_t slivhtlv 2. 5 2. 9 3. 8 .s .1 1.4 . or- .6 .6 3 .7 . ~.5 11 • • . 1 C' ;. in the C'•.rbon a fter emission shown in f1°:.rent h8s :i_"' . rn:,on the ba.s is of th.i.R tablP-, the c ;-en,;inr; ti.-rne 2nd current v:as ,ot-"ncm rci zec Rt ' 5U me. oer Cl'Jrbon( P, current density of .s.iJait 7 m,J ./cm. ' for V'3B), F:.nd a time of :50 minutes. The e.vsrc,£'. e ootenti a l P.p ,>lifoC' "cross the electrode,:, of the cell for 6 carbons in the holder ~,e.1; 1~. vol ts, enc 1 the totn.l current . ;.:; 2Jnfl. The charging V18 s ci.one in a tv:o liter iJee,ier. 'l'he ce. thoo e '-''8.s t, carbon rod imd the J-:.ol r, er for t '.1 e cr,r rien: to be t 't tCi.e o.noc-e is shown in f:l.17. f-1. nnii 'l'he end r,lr-::tes ?nd cornect5n/2" piece "rP ot.' b-?.kelite the t 1·ro rods of c ·rbon ere covered vd th · hr" ffin exce: :t for notches e.g~inst ,vhicn t·,e CB.rriers F.tre held bv a ruo.,er ·ounc. ""he rubber band ;Julls the mi6.ole of t: 1e c.-;rrier to"'RTd the projection on 0 ti:1e connecting r;j_ece, tlms hold.in~ tt.e Ce1rrier firmly agein '. :t t:.1e notch 0 in t .rie carbon rod. at each end, for cont,,ct. This arrrrne-ement ws.s found to fr,ivu e. uniform ~1ctivity to citrbons charged togetr1er. To 13. ttempt to increase the activity of the Cc.rriers, the cr;rbons with reduced silver were c1m.rged with hyci rogen ns a cathode before oeini;- r iven the usu?.l ;:moC: ic tre.cctment. C&thocic tre·'i. tment might remove loosel;r adsorbed oxyg en n.nd l.e&.ve sp,::ce for r:1Dre c.ctive electrolvtic oxv0:en. 'i'his tre a tment did not eJ'fect the ~,mount of :c-ilver emitteo. 'Phe electrolvtic r:ction te.:-:cs ,,lace throur hout the c2.rbon (76) (71) ( 5·')) 8.S SfiO"m ·ocr the followirw 8X')fTiment. i1. ' 'S'S C-":rbon l I! X i:l mm r_;_j_Rmeter Nas cut to a smaller size :=.,t various sti, ,.:rec; in the ur oce,; c: 1 bv cuttiwz the c.ir;.r,1 eter to 5 mm in a. l n the e.nd cutti:rw l mm from e r. ch end. Uncut, the silver given off ,vus 4.5 mq.: cut to SH!Fillt=-r si7,e before silver nitrn tP imnre£nr,tion, c .I) ma.: cut c;fter jn, m •ef!nRti on, 1. 1·i me·; cut E1.fter reduction, 1.1 1,iP.; e.nd cut after c <ere-inf!', :.. 7 mp. The surf8.ce of the m,cut CP.rbon v12.s 7.5 cm Bnd its volumP l.;:.:; cm.3, -0- -, 0 0 the surfP. ce of the cut c •:irbon Tr,s 4 . n cm' , the volurue . 4;.; cm· '. The gre11t er r e l ,.t i ve t,.ctivity of t he c'.:.i. r b on cut ::oft rr 0 C11">.rf:.in.: is riro·o b l v c.ue to cutting ofi' a n outer shell f r on; ,;hj_ ci:1 th e s ilve r ::: electroly tic-9.l ly r s mov ed . 0 . ~: been '::'hi s .Li::.•;d to ::m "J.ttemp t t •J c :,Ei r ge t r:e ca r bons 1":itr10ut tt1e 12.r ge e l e ctrolytic los s by usim·; t he ;,ro ,;erty of the electrolvtic a.ction t aking pl '.'t c e , to some extent & t h ,2. ~:t, thr owthout the car bon. A lfiiSB cc,r bon waF: char2"6d bv the inserti on of 2. f.: ilv er wir e c.s.t hode along the axi s of the hole in t1E c ente r. ·J nly . 6 mg. v·•a s oo t.,rdned fro m th r. s i l ve r emi ss ion. In an e ff ort to imorove t he araour:.t of efi1i tt: :1ol e silve r cornom•eci to the :silver .ie ft es r csir;ue Aft er emisc'ion (r:f. T;cole VT), longe r charf;in~ times v;ere tried ,. '.''i th the fo llov.::i_rJ£ si lver erni tted : Y) 1 '. i th 67 minutes and longer (76) t r,e r e wro.s ", li.2'ht or ovm co lor j_n t rn emi s ~i on (45) (78) (61) ( 58) (74) , t hou~h & browu color i s not n e c c"; °' sar y for t he existence of such :oro:i uct s ( 4S ) ( :, (~) to be formec . :~ilver in Ca rrier ut Vari ou s St ages of Pr e ~,,:.. r ,0.tion am.. Us8 . An idec, of the fate of the s ilver im pr e rw :1.t ed into tiie c ~: rbon by s ilver nitra te or ,at t he fa ctory (<' c,::,rborn ) shO1', S t he de :if::'naen ce on t he Droce r s used . Tnbl e VIIT ;;nd fif . 2 s no~,, tnP. nrnount o f s ilver orig in<,.l ly in the carrie r , the s11notmt los t by charging , t he n!:lount reme.ining i n t he ca rb on ,.f t E:r c har virn: , the emi ::;s ion in 5/ r: h our s oa k in distilled v,,ater, c1n d the r esi due re maing afte r '"mi ~~s ion. 'J'he si l V8r '-''P..S deter ,dneci. by the usual P. shing . Conside r able v:,ric.ti on in si1v r"r con t ent of t l,os f8 ctory pr e ,xcred. v:a.s n oted . :'. 'i th the c hc.r ging of ::i ~; CDrbon s , n:::, ch·::.n 0·e of1 el ectr olvte, e,n averae;e of ;:_:;__ mg . of silver lo '.".s t),ll c n.-'J.r1':inv ,,ro s foun c b ;r H:i ;.,· hinP." t he ! ';! H ~ 1li JW1++!-+Hi-+!t19114j, ' '! !1 1ll -I :,: I .)l -frfH •. t :;!. ·r; ' I ;, .' .. :t ti +Ell .;. : il' , . :..; _, r l!. Ll . • H l i tl rT'! :i: f, •---r-t --~ •• ., .. : . : ;~ cj:: _•;: ::.. :± i:t'"" ~:t :, .:C f=l :;-;-q , ·7B . ::i Ri l ver obt;j_ned from fi1. t eri rn::r t he electrol7tE· : ..nc ,._,,1-,,hin;C",, frorn t i1e cat hode. ·shi ch 1/3 is u s eci in the ce.se of w::,3 ( ':'i::ble VTT) to t r. r:e '.':'ilvsr from charg ing n,.,,r nv cic1.rbons TFoP.checJ .L 5 mp . /cc. in 011 1:: in<;;tw ,ce. Untrer-:ted. c ,:,_rb :Jns, or carb on2 vdth no sL. ver uut 2" :iven the usunl :, nocic tre::,trnent, when l r:.t 8r soo.f;eo in cJistiiLe<:, w2:ter v ive ;a_ s11,;,JJ_ .•, mount of silvet·, lP-s .·. t , en a tota l of 1 0 1<c:.1,u,:,a , unlt:e:,1:; the f::lectr ,l vte srioulc. re6.Ch conc~intra.t::ons of t..ne orcer men tion c o ::; oove . The pri o f t h e Fffects of t he "?lectrolvte. 'T'he concentrs tion of H •'; •.:()4 in the Pl e ctrolyte nas bee n w 1ried from .45 N to . 001 2 l'!, there i s<: v,:;rintion in silver emi':-.s ion likev·ise , r:' ro r.nine: f rom 4 . H to ;5 . 7 rnz . Th 0. Hmount of sul fur ic >:'. Cic !"'Y "' ,;r;en t t:en sot.ked in 6 istiU. ed water for 3 /;. hr . :.rnc, the nl!. of t ! k ; v,;eter measured. All pH measuremf?.: nts were H :.c e ,·!ith a T,eeos ' Uinrw(rone pH notentiometer. <md. Nort hrup From the DF t he c1.mo1mt of s ulfuric Bcir..: c an be c:·,.lcuL..,ted ::i.r,c fror,1 this t he e r, uiw1.l en t mnount 1) f silver in rni:c: ., c ~:.r bons so~'.teo. only in the eJ..ec trolvte (no si.i.v P.r) n ·-•u R silver e •uiv::1.l ent from 1, . ~ to ,. .LO to 27 5 mg . over t he ab ove vc:.ri tion of H so4 con c e nt r a tion . 2 P.n unus ed. un s oak ed in ele ctrolv te cio.rbon r educed the pH to ~: . 5- ?. . 4 (s e <:c> oelov1) , or a silver e,i ui valent of 5. 8 t1g . There i s a m;;,r ke6. incr e a s e of concentr ation of sulfate ions due to the c hn,rf! i ng . (76) (?9) (80) 1t is kn own t hpt t he va r i ous f,lectroly t es pr ouuce different r e a ctions a t the anode in el e ctrolytic proce sses (75 ) . This is par ti cul a.rly true with ca r b on ele c t r odes (38 ) (50) (74 ) (78) (-51 ) (81) (45) , . a.nd of cou r se dep ends on whet er tr1e electrode t ake s pR r t in the r e a ct i on (8 ~) . The e f fe ct of t he kind of e l ectrol yte u <e1 ed in c ha r ging , on t he a ctivi t y , i s s hown in Te.ble VIII gi ving vari ous ele ctrol y t es , a ll in t he r an e; e . 01--.02 l'J . The ordi ne r y f i gure for t r:A s olubili t v of the c orre sponding salt of the 8lectrolyt e a n·on (in 10 cc.) is als o g i ven . A gr ea ter e mi ssion (3 . 5 mg . ) can be obt a.inea. from the chl oride s olutions (as 1ith the s ulfa te ) if a carri er with mor e i mpr egna ted silve r is u sed . Other exr;;erimen t s have sh avm t h<i.t t he effect i s inde pe ndent of t !-:e c r.1.tion of the electroly te; ba.r ium , a mmonium and s oo.ium hydroxic.ie s .,, e r e the s"3.me witiiin e xp erimenta l error, ferrou s sulfa t e and sul fu.ric a c id, soclj_um chloride and hydrochlor i c a cid . ·:hen the electrolyte i s r aCl or ~{el the carbon anode lib er a te s 11 chlorine ( smella.ble) in s tead of oxyg E.:n been.us e c hlorine has a lov-:er dis cha r ge potenti a l t han oxygen ( 9~ ) (93 ) . In time , h owe ver, oxygen a nd 1:0 2 tend t o be develop ed along wi th chl orine (94) (96) (102 ) (10::i ), t he proportion de pend ing on the conditions (95) (77 ), c hlor a te s a.re for med . nd rri th oxy~en The ordina r y s oluoili t y of Ag Cl (97) or the f orma tion of silv er compl exes (98 ) (99 ) (100 ) (104) s eems to be inade• ua te 1 t o e;c, l a in t he hi gh amount s of silver emis si on f rom ca r r ier s chr-.rged 28 in a chloride electrolyte, silver chlorate, however, is very soluble. The oxidizing action of chlorine has been used to prepare silver for oligodynamic purpqses. (101) 'Ihe electrolyte used talces on the color of the corresponding silver salt of the anion, especially if the salt be relatively insoluble. The sulfate leaves a clear solution; chloride, a white cloud and white covering on the carbon; carbonate, brown in the top of the cell, while below; thiosulfate, dark brown crust on the carbons and some bro"l'!!l in solution; phosphate, bro ,.n above and lemon yellow below in bot tom of the beaker; borate (hot saturated solution had to be us ed to get sufficient current), slight b\.own; hydroxides, brown; citrate, greenish brown; acetate, light brown. Since the carbon itself can increase the hydrogen-ion concentration, distilled water can be used as a charging electrolyte. This property of carbon, to raise or lower the pH, is due to the formation of acidic or basic oxides and is determined by the temperature to which the carbon has been heated. (83) (84) (85) (64) (86) (87) (88) (90) (91) 11 If completely outgassed ch.arcoe.l is treated with oxygen, the surface is covered with oxides, whose properti es de pend on the temperature and pressure of the treatment. These oxides will absorb from solution con- siderable quantities of acid,. and sometimes also of alkali (i.e. they are sometimes amphoteric (89)). The actual proportions of acid and alka.li.absorbable depends on the temperature and presi::ure of the treatment with oxygen. 11 (37) Those oxides formed in the 450° are acid in character. (85) (85) This property of carbon in lowering the pH was utilized by making the water conducting (pH 3.8), with an mused carbon, in a copper rn cy lind er 3/2 11 in d ie.meter and ~" dee p . t, C8.r b on so c harge d em j tted only 1/5 t hat of a ca.rbon simila.rly c har ged u s.ing s ul furic a c:i.d electrolyte. Difficulty wa s experience in ke eping the current density high enough, the re s i s t1mce of t he electrol:rte increa s ed r api d ly when a current was passed thr::>ugh, a. t t he end of c hnr gi n g wa s 6500 ohms. The concentration of silver in thi s small c ell wa s 9-(/cc. a fter char ginf one ca rbon. 30 P. Physico- Chemical Prooert iE-,s of PreDa r ed Carri e r. 1. Rate of Emission. 2 . Stabili tv of E.mi tted Si lver in Solution. The rat e at which the silver is given out by the carri er is found by measuring the a.mount of silver in succes s ive hal f-hour periods . l'ihen t he l og of the amount of silver emitteo in a ha lf hour is pl otted agai ns t log 0~ the time the rele tion seems to be a stra i ght line, whether the s ilver comes from a c h?.r ge - carrier (fig . 1), or fro m just s oe.k ing t he ca,rbon in a silver salt s olution (fig . 9 ), when a lmo s t as much silver comes out as vms a daed in impregnrt ti on. A property of wat er irith the emitted silv er is s t 1i bili ty since the concentration a fter m~ny day s r emains t he s ~~me , a nd t here is no vis' ble preci pit a tion. Anoth er characteristic i s tha t s trong positive r eactions are found when te ~ted for the pr ese nce of t he a nion used in the charf!ing electrolyte. Barium nitra t e , for examole, give ~ a pre- Ci:?ita te 'lith carbons chRr ged in sul fo.t e or car bona te electrolyte s but not with nitrates . This inay be ex ected since the dr y ca rrier ab s orb s electrolyte s , the concentration of action in c har ging (p . 2.6) . (hi.ch i s furt her i ncr,,ased by t he The amount of s ulfa t e a nion i n t he emis s i on tube in t he ca s e of sulfuric a cid was found to be a bout t rn.t neces sar y for t he silver to be in the f orm of R sulfa t e . A t er:; t was made by determining the amount of emit ted silver in the 10 c c . (by r hodanine ) , t hen making a solution of t he same concentra tion of s i l ver using silver sulfa te. The t wo were te s ted for amount of s ulfa te u s ing barium nitra te. The amount of pr e cipita ted materia l was a b out t he same . The sul fate solubih tv limit wa s not ex€ eded oy s oaxing 100 mil'. A Emission 9 8 7 6 5 4 3 " 2 ~•-· ' Ii i 0 = ~ :¼ . I• lr1 ~ l,iic 2 9 ~ A 7 ' - ~'' ~ '" w., 4 ; ->-~ ·tr -~ :F - ' t- I 'I I 11 I t:l+ I .. ::: -•+ 4 t ,_.. it-- 8:: tJr L' + ~, ·Hh ..: I + -t • ++ 11 +-t-tt-,-r+-,, ·+ .,. ~ t~ >'• •- 1 t t--t ft t a 4 S 6 7 8 9 10 2 :1 ~~! a i "· ,,. + ~~ ~-,.: l I- ~LJ ~ ...' +,+ 4 5 ·+ i1 ~ L Ii- I 6 7 II L •- 8 9 10 II II - .... 2 a • 5 S 7 I 9 1Q si::r. c2.r b on s ( em h· c:i on of B m~-- .) in ~ucce- ? ion 5n 8 cc. rfj_nq 1 vol. 5 cc. ) t he 1'-'tq t oe reduction in volume of t :,e v•<> t er from thEi fin:;t to lest ccir bon i s t 8.l<en into account. The r;1ea.sur ec) con centnJtion v:es 5 . 5 mg. _::g/cc. (the solubi1i ty of silver in silver r-rnLfnte e.t ::,cJ°). <' i th t he c !-:loride, hydrox ide ,;i.nd nho sph-3.t e (th:io s ul fr t,e uro b.'. '.OJ.'.r oxid:Lzed to sulfate) tne usual fivure for solubility of the s.s.lt is e xce ocied . 103 mg. silver m·:i de 2.nu 3 rnf' . si1ver cBrbonr.te v·ere eF, ch soaked j_n 10 cc. distiEeu v-,ater. 'T'he concentr :J.tion in t he oxide ca se , ," lfter .U· mi:;. !cc or l. ? mg. in s ol 1.1tion (e xrec ted 9.mount. f rom A. ,ireek, wr-is the usu.s.l figure for solubiE tY • : . mg. in tne snme voJ_u me ); t he silv0r concentrntion in the carbonate after 3 days w;::is .11 rr.g. /cc. or 1.1 mg. in solution ( coi!2oared to . : 5 mg.) :1'h8.tever t he r eas on for thi : :', ap :Jarent higher value it is "'uff'icient to remove the difficulty in the amounts found for ca.rbona te and hydrox 5-de electro1,,·si s in T"l.ble VIE. Any substance v,hich 111il l ,jrP.ci : :J i t a te s j l ver (9) su ch as T:f, ? n ,;, turally C r ~moves the silver from solution. A fine aluminium um•1der of several cc. volume was shR.ken for 15 minutes w:i th 10 cc. o i s tillec: vm. ter v,hich had h8.d 1 rr:g./cc ,~>7_ as silver _nitr~, te adc1ed . After t his D8 riod no silver was detectable in the V.'~ter v:ith the rhodn.nine te s t. The em ;.ssion of silver is not aff ected by the nresence of n eutral salts. KtTOr- in .5 mg/cc. did n ot affe ct the initial eff,hrnion nor v,,as it ::i able to re .cwtivate a carbon which }w.d oeen s oake(1 for 5 cays in wa ter only . There was no marked variation in t he total emissio:r; i 11hen the volume of water varied from 10 cc. to 8 liters. a . Time a nd Storage Cond itions. The a c t ivity of the ca rbon carr ier s i s no t s.f i €'c t ed by s t or 2.;'e und8r or<ii na r y c one i tio1•s . .',ome ca r bons (2. protot;r uc ':-:i t n 75 :· er c ent 1 l Arnnbl a ck) v,·ere or en:,:.re6 in 19 ii9 by i"Oak ing i n a 1() ~nerce nt s ilver nitrR.te solution, reduced by j u s t h ea ting to r e d .ri.ef: t in <i. cruciole, then char ged v;ith a current of 10 ma . for 1 5 min s . These c a r b ons I nd i a <i.nd b9.ck by T1r. R. /' . fi l 'L ik1rn. i1 Thour:h t here V-'!t " 8. varia t ion of a lmos t :;;() oercent bet,.·,een ino. ividu al cnr b on s, t ne aver ':'ge efr, is s i on 1 939 . The relr.· tion betwer:on t he a mount of s i l ver a.no c r.ar g i ng concii tions vras such tha t a rec t·a r P-:e (irdthou t e miss i on ) a.t 10 ma . for 1 0 mins ., or 5 () ma . for '37 rni ns . a ll g;,;.v e the s cn c a mount s of s i l v er, v.·:i.t hin an '3.ver1::.ge of 5 percent, !:l. s t he ca r b ons v:hich :me been gi v en no f urther tre~, tment llfter s toring . ~nother set of sta n dard ca rbons we re s to re ci f or ~,e rioo ~, un to 9 months under the followi."1g va ri ed cond itions ; v,T "WCE:Ci in c ellophrme , sealed in e. i!l ass tube ab ove s olid s od i w.i hydrox i de (to r0.rnove v,.,,_ t er), in a gl2.ss s eale d tube wi t h ca lcium c hloride in a 10- ::· mm H2: pr essure v a cuum, 2nd in a s ea l ed gl ass tube -:,b ove ab out 1 c c . of se. t v r •➔. t eo P Q wB.t er. These carb ons when rnaae :t:.o.d P,n emi sf' ion·o f 4 . 5 to 5 . 0 mg . /l,g in 3/'? hr s . !l.f t er 9 months in vrr :i•1red cel l onhane and dr y a. i r ~t or ed carb ons ,,,_,er e un a f f ected , t hose i n v.s. cuum sli r)1t i_y le s ~ ,;ctive , noout 3 .7 mg . i\ g , a nd those wtt h ~Ir:~ ge.ve , i n one inf' t nn ce , . l mf! . 2.nci J )0:' .5 mg . in :mother, t he 7-! S ca r bon t e,;t ed a t t wo mon t hs g::.v e . 8 mg . The 2 rr,,. s ca r b ons unfor t une, tely v: ere al l wetted by the ' 1a t er . :fo ,:,rnell of r' l{.(-_, c' was or s sent wh en the tu·oes we re openeci ; a "'.Jpar entl7 t n.erP hc: d . been 8Uff icient s ilver to r emove t he s ulfi6 e ,;n o f: ti j_l "~•.ve PO~r!e a cti ve s tlver J_eft . r'hemj_ c3.l. In adoi tion to the :{ ,:, poi s oninr; just mentioneo , t he CB.rrier s 2 c : :; n &l so be poi s oned oy s o,~kir. s in a l ,',ercent ,,r~cl sol1J t ion, oroth or T)enton e, f or e:xe..mnle. The noi s or: i u_r ''.'8c, v e r v ffo1.r keci c,f t e r l min . exn osure and 1r) or t, 0 min°' . ne1:1.rl sr d_P" tro:ver: it. ca rrier s c:rn be r -9activa t ed b~,r 'i' ·;es e noiconed rech::,r f! in r.7 , R.lt t,ougr1 ti1.i s :is nst a s ef f'e ctive c1.s the orhrirn:;, l urrnoisoned c: ;.rri er . The arnount t i1e r en ct- re sult holds for s hort, low chr-:.r gin g conai tion s , wj t h the s t:c:. ndr,r d char ge it i s diff erent. C-?.rbors ~dvin c- :1 .l ms- . r:v er1•ve ···i:en r eche.rged p .ve an average of 1. 5 l!lf". . ad,.- itione l; if retr ee.t eo t• fte r emi s,don , they gnve a n P..vera,v.e of . 8 mr . !'-. f! more t nn.n d i o t he fir s t time . The a sh from the onl~r r E: c harged ,'as ? • ? nw ., VThi l e fr om the r e tr P. ::i.ted a nd C;a thooic Reduction. The a ctivity may be oestro,red ;y,r c h~r ginE<- t he st,_,no a r a carbon cat hod ically , ':i.S sriovn oy the follo,: in v t,m ic2. l fhures (5!) ma .); no 0 Re1:<. ting. The destructi on of '3 ctivit;v by ht:Pt i s s i10 \rn i n f i g . 10 ,,.' ht:r e sulfuric aci o a nd s oci1Jin c~i.r oor. , te el1:;ctroly t es n.re sr..m,n. Thie; ,,1r, y be 34 cori ,:,ar ed to fi~. 3 , the etifferenc e beinv in tne int j_rnct CV oi coriti:tct oe t mr., en t i1e s ilver b n ct c.c, rbon. C:,;.ri:, on c::1rrier s :3 0 2.Keu in s ilver salts /:J.nd i·1ec:,.ted s hov, ttLts same 6estruction of ~Ictivi t\T (rF:: c, uction) ab ove 4oo0 • 'T'he e1ectroc1e notentiF:.11° of the vecri )usly trF'"' t eci or u.ntre~' tee 1 cPrbons ,-,ere rnec.sured ? 1:i th r s s,,ect to e ,'. Ch oth er 8no rnetell.ic silve r cy --:::,or; s· endorf f 1 s com penr~ition methoo (JJ )5) . ;,hile & C(;Ul'>t te ele ctrod e ootentir,J. value ~, ar e not to oe ex ,;ected wit ho ut consideraole eff ort in ri r;ic:tlY control1 6d conditior" , :v.ct th e fip; ure ::3 P' iven e .r(-1 orob>blv ,,.,.ell wi t..1-iin the corre ct oroer of magn i tucie , in vol t f~ , s n 0 1·cn in fie: . 11 . + /'.FI, - - - - .07-.14 ~ - rec. fiv . 11 Electroc.e Potenti.<1.ls of ()-,rrier s TI ::.:::_/ =i='J:L •-• 'l-1 '.L~· .. I n• lli •~:1 i:'. :j_l 1 +:-'t-f ~i. . :-· ~ ~tii 'fl+H-H-H++-H~ :f,.:-. - ;~-~ F:11_1:: ,. r I]. ~ - "' -~: i ,..,I irtl it h• • I'. ·: 1 -i-· :;• .:!. t!! . . :T:;+ -+ L .S ,!'.: I ~: 't. .iJ.· 1· f--~ ·• . . ~· . •-~j-; j :..w ::! 1m1:r:1+1r:H t ;:~:~..., ~i •.l.::: .. , ..,i-•I ..i 'I t ' . fl f-i-i:":,; i "T • '·1I'i[+ Ji:+ ..., • :-i•.i. _j • ,7TI ·:: ':+ ' ·it, .. .. :'~ ¼l-+"'+ : rm-: +L ·~· + it l • ''+ :i:: :-: .. '. ·-•·. ~- . ·- 13 -i- !Jl' ..:m .1 ,... .11 - :-t:.i ;t~ ..... :..::+ EE , t: :~t! • !J I-++• al :nri -!+ t·•· ,.. ,... + !:i! ;~ ~ l. :i; 'it r.; k =i :! :J.i :: .... t tt .. ' >,rn : ! #~ r.: :5-:"'!-~ ·:_r. t ,.,. rmHl+fHfFFfl-Jµi ':> ~~:.i. ' !"':....H-H-H++-H++lf+l-hH++lf+I-++:: ~: •-• I ! I t. ' .. ; !t.1 ~ f: l lff+l-lH+f+-1 j : :: :;1 1:•-...... .. "; h:+' ltH-H++-H-H-IH+HH-++11 1-' c +< L.i ::i:i~ ·: !tt 1 ·: ·-:1:: ,. f-,• I. .,. I+ "" 1 rr .fT i + E I .H-1 ~- ~t il= ! ~:+. '!" t.I.: 11 .. 1 r ri : ' J tJ t l:ti i ·::1 +:..1 _ii ri:t "';'ii q :~ ;ijH i 3,5 In order for '. ,ilver, in its r eouced state, to l[O into solution, an oxio.e.tion, i.e.> th(s r emow:i l of ele ctrons of t ~1:- rnet<i.l, rnust tRke •Jlsce. F'l'°' ctrolyticallv this mev be eces cribeo tn the folloi;-irw term" (106): "At the anode, vrrhere electrons ·,.,asp frorn t ne solution to the wire, s orne substrmce is oxidi7,ed . Ttd_s oxic) n.tion mny be the liberr,. tion of oxygGn p;as , the l:\bern tion of he.lo;::Pn g,c;_s, tte dissolving of a rnete.l electrode, the oe~Josition of' a hi r:- her oxide :=mch a::-. Yon,., or ( ",'Ylo2 u rJon the ~mode, or the oxic 'J tion of some s ubr;t~nc e Drec- e nt in. the electrolyzed solution such R p. a fer r ous c;8l t. The c[,.rbon silver C?.rrier rhen macie t he r:noue is l:l. surf~,.ce ex oosing bot h sil ver ana c2rbon to t:1e el8ctroly-te. Carbon o oe s not f orm an ion an ci. go i nto s olution ( 4b) , but silver ciOes . Gas , oxygsn or chlori ne , C)l "' o ma.y be evolved. and ac1so1·oed . In the conc'ii tions in stanc2.rd ·,)r e ,')i:.r.c-. tion l a r ge .3 rnount0 of oxvrrem ,.f f e nd sorbP-d . The rels.tion of silver to oxygen mav be brh,fl7 consic.e reci. . .C'. ilver finP.l:v c3.is·:rnrsed form a. s po,·,oer . (107) (lns) (l,'! J ) (11 ') ) (111) The '; U8.nt i ties of silvo,r ,_,,1-,jch RO int0 solution f roni s11ch P.n r-..ctiv1:1tion n.re f,:,_r too smn 11, evc.n though fr0m the hcnt of acisor ption th<? ·:.c.d sorDtion of oxvusn rF oxide (11 2: ). P,t the silw, r is 8.ctuPlJ.Y %;_ c:1emic ul com·oin·,tion e:c: c-"i:l.ver i 'hen silver, "l.s in the ce se of ot, ier rr:et::, j_~, fr rnf'l.d/3 ~mode potentfo..ls belo··.· t)-r-1 t of the deco1i,Dosi ti un po t t-;nti,-1 1 of wa ter, oxi 6e polariz¾-tion fil1: :s ":.re formed or,, the surfn ce (lL; ) (l.l.4 1. Unc,er c e rtain condi tion.s n:i.r; her oxida tion 2t• ,t ec o t' sLLver, u-9.rticui1:1rlv oxiC: s , be ·Jrormceo s.t t,,e 1mocle . (l:>4) lff :f (116) (J.17) (Ub) (U,➔) (1:::'l) (Ul) (lr; ? ) (Lo) The i1ig,her o:xice r: of s ilver 'lre stron , oxL izinr ,, r, P.ntf' (L,'.', j •md decomDose U.l'lder the influence of wa ter. 'rhe ,-, e pr,i 1 ts ,,r t; not obt-:'1.inec in pure form, out ru:we tne si l ver s :::lt of t ne electroJ_yte included in V"X:Vinp: qwintities (5S). These n_i. v:1P-r oxic1E"" T!,riv 01- the source of t he active silver. us inf! a c,:i.rbon n.te electrol•rte (115). 11 'hP exi s ter, ce of s ub oxides of to l' g , o+ h'3.ve been r enorted , t ut t her e i. s cons ider-9.b le • I'..' doubt concerninf not onlv the exi s tence but e ::;ue ciri llv t he s tc1.bili t:v in solution. T~wle.tion of t hem hlls not been R.ccomnli s bed . (5b) (114) Oxyf?en p;e.~ itself h:'3. s not an a :.JnreciBblR 1:1 .CtivPt"ine ef; ect on the carrier ( n. f ?.). Fro;-, the enerv. y con s ider,, tions it i s to be ex uectei:! free ener2-y of !• g ,_r) i" - 2 59:.J c:::i.1./mol. anc, t rn.,t oi CO - ,_, .,Jl u , r,nC:t •. CO,:.. - 9 1·450, (1 25), ~m 0 t he il er-> t of e.d sorntion of oxvrc'.Pn on C,!rbon vJCJries, c.eoendinp.; on the J,d nci of a.d .s or:•tion, u~.1 to 64 , 'J j_-; c, ,1./mol. on t ;1,e C:-?.rbon ~·:ill not h :.:tV ' ' the ener p-~-.r to c.'enct s i Lve r i nto s oluti o!'l, in f a ct, to rn<:. v::e the follov·in ~- r"nctiori 4. fJ,g (met ·i lJ.ic) + ()I ,roce ed ~ + ? (··ds:Jb 06 ) 'r-.7 , ,' )')!) C8.J.• ./nol. (nep-lectin;;,: the lar q,e e.rnount n E: Ce','. :'"T v in enerpy to 6esor'o the oxvgE:n) v•ould be r, e er;ed , t his i ::, r,, 1J iv- lLnt to D. :-. volt. 1 0 m1ms to w:d-::e a local element f unction in orc f:: r to s end silve r into 'The oxic.'<tion ,m,rnr of c.s,rbon i ::; gen er u.LLY nscribec. to t he c nemisorbed b.yer of o:x-ygen on its ,:,ur fr: c e ( 8::, ) ( l r:'.'. j) . The ca t c:tl:vtic e.ctivi t y is o.etermined o:v the s tructura l t 7pe of the carbon (1 5;)) , and is an 00timum f or the a cid ic t :rpe of Pur fi,,ce ( 85 ), thi s f its wit:i the s uperioritv of l nmribb ck ,,.q rbon r of the tyne used. The effe ct of diff erent electrolv te s ma-· Le pe,rtly ex ,1a ined bv the forrrtRtion of obstructin;:· films (lfl) . Thot~R'h ce.rbon forms many tyries of bond s with oxypen (L~3 ) (/,7 ) (41) (64 ) (13~·) (86) Uib) (56) (P-i :C:, ) (1:s ~; ), ther e i s one t vne of na rticul8.r interest. There i s a, ori rnE.r y ox ide of bb d'~ c,:.rbon form ec:'i bv elPctro- l"tic oxi<l8.tion (:i8) (56) (1 CS::' ) wri ch is ,.,. str on P' oxidizing -?sent and who s e form!'>..tion va ri e,s wit h the electroly t e:: m :ed . "rhii.e the clrn.ra cter of t he err:ittsd e.ilver is not yet cs rt'.'·in , it i s not ~rob~ble th"l t it is emitted in t he fo rm of ?. !1ydroxic e, since thi s , in a. .s atur •. ted solution, hns " i,i~~ i3 .t; I l~•'.-), r.nc t h e emi tt.ed si lver s o Lution -=: ?Te ':c~!,·:avs a cic , irre:=: -:- ecti ve of the electrol7 te used.. 38 /1 nrocess has been developed, in v; d.ch a c ·, rbon carrier comnosed mostl;r of h trnpb le.ck is u s ec5, to obt;::,, in a source of s i l ver for oliiiodvnamic action. The oroces s consi,:- t s of: :i.mpref?ns ti1.1.g t he ce.r oon wit h silver ni tr'3.te ~o l uti.on !'i nc reo ucirw t he s ilver to R. finel y r3 is ner sed fo rm in t ne electrolytic':'J.lv a s a.noc:.e . mec hB.nism :i_ ,-, CETl)on tN he,,, tir:F , ,: nd c h,,, r pi rw Throuf!h t l:is o:Yic1.<' tion nrocecc T!10"'e not yet U11r~er s torxI , t t e cr> r·oon si l v e r C"rrie r i.s i:-.ctiv;:i ted so t ha t :i.t v.- ill e;d t s i .Lve r ·,i.n en t he cnrri er is in •1,,9 ter . P...nd The nr er,"r P-d ca rrier i s unf' f fecte6 ov l1ee t U l) '.C O" keo to ;,);)()° C. it ret::::. i ns its i:t ctivi t ,.r over periocs of mor e tr w n a. yHr . :f, H ~ I TT :! :i J ; ':r::. i::' · -:- t ~ ''•--. • ,~ ::1 4 +: :.· ::. ,,;r'l l:i , • • :t [ .., '"" ~ • " .., l "'I '1 ] l :+- ::: '-·· P+l ~..:1.00 u -+-· : .. ';. >t ._ . : " ·- 1 11 . :i't :I H .= = =a - I .TT: i! ~i1 ~ ": . ~ : t:-: . .L:.i . '" SQO .' ~..; -i rt I :l±t± ::~~ ... .... : •;;. ii::i H ti -- ,r ··~ C, .u ... .I • ! :c:. !U : ! : ~ ,_ ~ i I!:~~ : i: r: ... tl 'l±Jc.=:. ~:::....'t::::i t -;+++~:' -n . t,t rl r-:, l...i , , . r .·, : : :t •r : -, !. : i ' : H :;_· " •L..... .... =f. l+:;,. :: ~i :t • 1.i(j !:" tri i t;.-::rl ~jii - .,, ·1 ±: _;_: ~. ti :t I ~ ? 7. Tl ~i': '-t+I-,""•,-++++H-,0 ~i i , -+ t~ +-i •. i •• I '. :i T: lj :1·1 :i t ;ff :J. , : , ~ :-1 ~ j 1-t ' ti l•.ll •; n ..., l+I - ':tt '. I .. tt l:+ . ~-:i i·;::- if ,__ ' . :i ffl _I ,j'. -I ~ r. ttt-t-1 t-r:tttt1 L.ll .. :. ~:i ~ .... . - :g I f ' . f' •~; A·· ,m ·p+j ii - 1:.::.: w, l:l- .. H· j H 11· . ·+ .. - .. .. + t' -+-';; ~~ .: . ;:;.. [1t1 ;i:; ·[~ i;.r. +-·". ·:: ,J~; ,. . • ~i -'-i .::r .··+t• f-i..i..,H H+ ., • t-:: 'f:~t 'f: :i fil.::" +• -- ;, :::.:1 b..:(:J=1 •-+• ., -· ... :.·± •(.~L::: +, l : , .• ...;'.!. ; :j: 'IH .' '4 !' .. 1: l .. ··:1 ., •: ~t:-,. -•· t)J =4 =h1 +''·i :rht ; ~n .ti! C .: •·• i 1... Ll " .'. jiifBij nl EHi t ., +···1'1 l: ' t+ ' h·t• ri i •~.;_; .:i i ·• rt :t:I ➔ ·- :tr ...l ' ·! " . •·•·• ......: ,.~: ..'" j I ·I •+ +! :ti ..-;:1 81}~ ~. ~ ..,_,, -+ =l:l :;.. l •=!:li' ..·:-+ ==i ti-! L F"''?..aci:=:veld, C. Y,., Chemisch 'i ee kb lad. ~"il, 4 :08 (Hk 4c) . 3 . Historv of uerocotus , l:, ch . .182 . rageli, A. 1 7. 0 c., I)enkschriften der s chreiz. nlo.turf. Gee' . :i : :, 1 (1893), iebeneicher;1 n. , •"."oll. ?. 59 , 115, ?4 ;, (193~-) . Fffect of Qilver ., ll :-c:i.lver i1, Inc'U:-trv, edited 1-, •• • ' 'T'oul, CoJ.l . 0 o' r T, . toci cks, r:2iriJ1 old . ze cho,:,lov2. K. !'hern. Com., l, 155 ' 7 'Z.) ( 7_y., ' • ll. U. ( . udent 306,54-7 . 14. U. 15. V 435,543. n. K. 2.9 , 04~). 16. F. Q 1,64?,)89~ 1,685, ~ na; u. 17 . u. ~ - ? , r:x36, 71n; n. Y-: . 43 7 ,UfJ . 18. TT '• r, 19. TT • " V. "- . 157,:-'8 •) ; TJ . \ . lri), :f/ 5 . ?l. U. ~. 384 ,46 6 . 24 . i;,cB£:.in, J. 30 . 0 r· ., The .c:on ,t:ion of Gase.s end Vri.nours bv :=' olios. :churnacher, J., 13ioc hem . 7 ., B4 , ?i.::l8 (19~_; ), bl. vr ~.inick, H. G. 7 r,.i ikrochemie , ~-6 , 15tl (l-213 ~) . 3? . (K"r~.u,: e , r', .) re s cr intion of th(, K.s.ta dyn hpparcitu s tor the Deter minP..tion of "'.ilv e r in '.· a.ts r. 4rJ . RandAll, J. (m imeogr !=!.,hed) . r., Diffraction of Y-"Pl':l.Y!" qnd 7".lectron s b, Am ornhous 0 41. "Ruff, o., Fara.day c; oc . Vosburgh, F. J ., F,lec. 4;5. :",troud, , :• F. ~ .Jr., in Duns ta.n et a.l., Science of Petroleum, iJxford Univ. Press, London (19::'i 8). i, ,:77'r: . 44. Gould, D. TT ., ibid. i, ~774. al i gemeine Chemie, ,YIII, ()t. , • Ake.derni s che v(~Thcf.J l,eipzig. (HJ'.'Sl). p . 549. 4f. Sproesser, L., Z. Sle ktroc nem. 1, 10~7 (19 01). 48. r ubinin, r·l . 1.1 ., 49 .. • • •,,,as ., n.ourn 1 E'· • ••• • , .J. Gen. Chem. (TJ. --:;. • • B.), 1, ~8~; (l do l). ~ J. f-'.ff1. C:era.rn. .-,·- oc., .''.:::, ".•v 16 (1~1 •·~' 1) • 51. Foerster, F ., F.lektroc !:e1Ttie v1e.s ~· erh·er l,os urw en, ee;. ,:, . B1;rth, l,ebzig . (1% ?). r:n. 450-51. 51. Sihvonen, V., Acta Chem. FennicP, _7.!}_, ::.:b IFFi4 ) . 54. Ger. ::il5, 031 , Cf. Koll. 7 . 5:-J, f 5 i: (FL'<.) . .5 '7' . F'ronrierz, .' '/ . 7lektroc ner:,. lT • 4 :'.i , 561 (19:-;7 ) . 59 . Yyronoulos, "' ., Z. !:l.n orq. c ;,ern. _ll:i:., 157 (F:2 ) ) • 4 64. Ls.rr.b ert, J. 8S. i'_. ~ellor, J. •~; ., P- Corr!prehen~.-i~,e Treati~e on Inorqc:nj_c arid 'T'heorPticPl 71. Ln ti ri:er, µilrtebr?nc, ~eference Bon~ of Inargnnic 74. Thi ele, >-T., ? . 1:'lektroc nem. 40, r.'.6 (18;,4). 13 oller, :·[ . D. Bur. of ,c,t?nd-.-c.;ci. Pi::oe:::·s, i!l, no. S04 (1\:l;.-5). 75. Gli;;.sstone, s., c>n o -''• Hicklin2", ·s:1ectrol,rtic )Y:ie'~tior: Pre Rer; uction. 74P..• 76. Sproe s~.e r, !,. , '.i • .Slektroc hem . 'J.., 10;,:? 1 1'::171 (l :Vll). 77. Joffe, ,• • )., 2. Flektrochem. 42, 71 (1936} . 78. ~,ihvonen, V., F'e.radP.y ~, oc. Trans. M, 106 :C:, (h:;'it, ). 7J. Kr em'lnn-illiller, or, . cit. o . ,57 ,1 . 81. Sihvonen, ·-..r. and P. ~ arkemi;c;s. :~uornen Xemistiledi (13) 11, 1 9 (Hi38). 5 83 . 1/"' ,'- lng , 84. King , •·,, 8£, . . c. C (H336 ) .' . . . . - (:c%7_) A.' 1 'eiser : T u T ~) (' ·, ' ' 1668 . 1489 . ·,. B., 85 . 101. TI . ~. 410 , 838 . ibiC . , ch~ . 6 1" ~. 3enton, J, . 11 ; . r ure.u, l ? l. r,_ be ,; r,:, F . e nd v. ~'uerb,,ch, Pr:n dbuch der anor f.'8 Di.c' c J·.is n Cnemi e , l'irzel, LI, 1, 70'7 ( l \Y)H). r,einzi 2: . . F • ' ant J. J elinek, 1/ . &n 0 T g . 1 ::'4-. irreme.nn-' ffliller, on . cit.., 1) ::, . 418-1::1 . ? -q. 1.18 . liniv . .::-ress (ht'.--F, ). D. ~W) . l:'.'> 1 . U:offmirnn , U. , :P . Groll and.,. . Lemc trn, L , ~,i,r e i:· . Criem . 44 , 841 (19::i1 L Vi2. P.i6ec: 1, f. 1<: ., ::e nc ,-- ,·:. ;, r i!!ht, .J . C. '"~ . l ~: 7, l ;':47 (1 & 5) . 1 - 5 . Foer s t e r, on. cit., o . ~41. l ;',4 . ;\'i iiller, J . H., tm . Dhil . f) oc. Droc. L7, :)' h {l'. -::,6 1.