Comparison of the silver and iodine voltameters and the determination of the Faraday

Vinal, G. W.; Bates, Stuart J.

doi:10.6028/bulletin.238

Cited by 22 publications

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“…However, 4 years earlier (in 1912) Washburn and Bates [ 3 ] had proposed an improved 2 iodine coulometer for which high reproducibility and accuracy were claimed. In 1914 Vinal and Bates [ 8 , 9 ] made a direct comparison of the silver and iodine coulometers in the laboratories of NBS and found that the two methods yielded different values for the faraday. Since the two types of coulometers were run in series the ratio of the results given by the two methods was independent of the electrical units and the durations of the runs.…”

Section: Introductionmentioning

confidence: 99%

Determination of the value of the faraday with a silver-perchloric acid coulometer

Craig¹,

Hoffman²,

Law³

et al. 1960

J. RES. NATL. BUR. STAN. SECT. A.

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An accurate value of t he faraday has bee n deter min ed by the e lectrolytic dissolution of metall ic silver in aq ueous solu tions of perchloric acid. Standards of electric curren t mass, a nd time a s maintained by t he National Bureau of Standards were utili zed in th~ determinatio ns. Th e electri c c l1l'rent was m easured in terms of th e standards of cle ctromotive force and electrical resistan ce. Silver of hi gh purity, freed fr om oxygen, was used.The value of t he faraday was found to be faraday = 96516.5 ± 2.4 coulombs gram -equival e nt-1 (physical scale). faraday = 96490.0 ± 2.4 coulombs gram -eq ui valent-1 (chemical scale) .These values were obtained usin g 107.9028 ± 0.001 3 and 107.8731 ± 0 .0013 for t h e atomic weigh t of silver on t h e phys ica l and ch e mical scales, resp ectively . ' The electrochemical eq uiva lent of sil ver was found to be electrochemical equivalent of s ilver = 1.117972 ± 0.000019 milligram coulomb-I.This value may be used in a n alternate meth od of defining t h e ampere in absolute value, llamely, t hat steady current which will d issolve 1.117972 milligrams of silver per seco nd a nd de pends only on t he standards of mass and t ime. The indicated un cer tainties are overa ll limi ts of error based on 95 percent co nfidence limi ts for t he mean an d a ll owan ces for t he effects of kn own sources of possible systematic errol'. I . IntroductionThe classic m ethod for the determination of the faraday involves the electrolytic deposition of silver on platinum from an aqueous solu tion of silve)' nitrate. This method h as been extensively studied and tmder closely sp ecified condi tions [1] 1 was used for many years in defining the international amper e. In the original work at th e National Bureau of Standards the national standards of electric current mass, and time were used, and great emphasis wa~ placed on the r eproducibility of the method as a ch eck on the stability of th e existing standards of electromotive for ce (Weston cell) and electrical r esistan ce (mercury ohm). In 1916 Rosa and Vinal [2] sum.-m arized th e work that h ad been done with the silver coulometer not only in yielding a value of the faraday but also in ftttaining conditions wherein reproducible r esults could be obtained. At th at time the consensus was th at tIl e silver coulome ter gave highly accurate as well ftS reproducible r esults and yielded a value of the faraday acc ura te to within 0.001 percent (10 ppm).However , 4 years earlier (in 1912) vVashburn and B ates [3 ] h ad proposed ftn improved 2 iodine coulom-1 F igures in brackets indicate the literature references at th e end of this paper. 2 T he iodine eoulometC!· bad bren studied earlier by H elTOtul [4]. D ann eel 15J, Kreider [6J , and Gallo l7J b ut tbese experimenters did not cla im higb aecm aey for t heir \vork .eter for which high reproducibility and accuracy wer e elaimed. In 1914 Vinal and B ates [8,9] made a direct comparison of the silver and iodine coulometer s in the labor atories of NBS and found that the two...

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Section: Introductionmentioning

confidence: 99%

Determination of the value of the faraday with a silver-perchloric acid coulometer

Craig¹,

Hoffman²,

Law³

et al. 1960

J. RES. NATL. BUR. STAN. SECT. A.

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“…Silver dissolution e,f based on the relation 1 NBS ampere = 1.000012 absolute ampere based on the relation 1 NBS ampere = 1.000011 absolute ampere based on the silver/iodide weight ratio [24,25] based on coulombs used to liberate iodine [24,25] based only on the vacuum values of Craig, Hoffman, Law, and Hamer [28] f using 107.8685 for the atomic weight of silver s value recommended by the National Academy of Sciences-National Research Council [23] calculated on the basis of the coulometric titration of ASpCU with electrogenerated iodine reported in [21] x values obtained in this work. 55 Accordingly, one must use the faraday on the "NBS" (legal) basis (96485.8 NBS C/g-equiv) .…”

Section: Analysis For Lead In Lead-tin-telluridementioning

confidence: 99%

“…After storing in a desiccator over phosphorous pentoxide for about 24 hours, samples weighing about 0.27 g were ashed slowly to 500°C.…”

Section: Analysis Of Lead and Zinc Cyclohexanebutyratesmentioning

confidence: 99%

Microchemical analysis section:

Taylor¹

1968

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“…In 19 16 Vinal and Bates [22,23 ] made a direc t co mpari so n of th e silve r a nd iodin e co ulom e te rs in th e la bora tori es of NBS . Th e silv er co ulome ter was used .. to es ta bli sh th e c harge in internati onal units and in 6 of 10 expe rim e nts th e inte rn a ti ona l co ul o mb s we re de termin ed direc tl y fro m th e dura ti on of th e run a nd > va lu es of s ta nd ard cell s a nd s ta nd a rd res is tors kn own in inte rn ati onal units.…”

Section: Iodide Oxidation Methodsmentioning

confidence: 99%

Resum of values of the Faraday

Hamer

1968

J. RES. NATL. BUR. STAN. SECT. A.

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A resu me is giv en of the de te rmin ations of th e va lu e of th e Faraday. Va lu es ob tained by sil ve r de positi on, iod ide ox id ati on, oxalate oxida ti on, th e o megat ron , a nd ilve r di sso lutio n are rev ie wed. Ali valu es a re converted to th e unified 12C inte rn a tional scale of ato mi c we ights us in g th e inte rnational a tom ic wei ghts of 1967. Va lu es of th e Faraday are given in terms of both th e NBS (legal) and abso lute unit s of elec tri cal measu re. In th e la tt e r th e new valu e for th e accele ration du e to grav it y is used in co m· puting th e absolute valu e of electri c curre nt. On thi s basis and using th e atomi c weight of silver de termin ed by Shi elds, Craig, a nd Dibeler, and co nve rtin g to th e I2C scale, the value of the Faraday is 96,486.9 ± 1.6 abso lute co ul ombs per gram·eq uival e nt whic h diffe rs by on ly 1 part per million from th e valu e recommended by th e Natio nal Academy of Scien ces -National Re searc h Coun cil. If the atomic weight of silver recommended in 1967 by th e International Atomic Weight Commission is used , th e Faraday on th e new grav ity value is 96,486.5 ± 1.6 absolute co ulombs per gram-equivalent whi c h diffe rs by 5 parts pe r milijon from th at reco mm e nded by th e National Academy of SciencesNa ti onal Resea rch Cou nc il. No c hange in th e va lu e of th e Fa raday a dopted by th e NAS -NRC Committ ee is reco m mended.Key Wo rds: Cou lom e ters; Faraday; in clusions in sil ver co ulometers; values of Faraday.In 1962 , Remy [1] 1 in a review article converted all publis hed values of th e Faraday to the 1961 unifi ed 12C scale of atomic weights. In so doin g, he used th e inte rnati onal atomic weights of 1961 and several inappropriate co nversio n fac tors. It is the purpose of thi s resume to clarify this matter and to brin g the where th e ± 0.001 represe nt s th e "experim e ntal un . certaint y" in th e atomic weight of silver.I values of the Faraday as de te rmin ed by various exAt t he tim e th e above definition was formulated it was realjzed that additi onal a nd more acc urate measure me nts were needed to place th e electri cal units more closely on the theoreti cal MKSA elec tromagn etic units. By 1948, after interruption s caused by the two World Wars and after improve ments in te chniques, an accurate determination of the electrical quantitie s in centim e ter-gram-second electromagnetic units was achieved and on January 1, 1948, changes from inte rnational to absolute units were officially made inte rnationally. These conversion factors for the volt, o hm , ampere, and coulomb were as follows: f peri me ntel's, up to da te. Intern ational atomic weights of 1967 a re used.

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Comparison of the silver and iodine voltameters and the determination of the Faraday

Abstract: Chemicals and solutions 429 3. Methods of standardization and analysis 431 4. vStrength of the standard arsenious acid solution 435 B. The silver voltameters 437 1. Forms used 437 2. Materials, eic 437 IV. Tables of results 438 V. Discussion of results

Cited by 22 publications

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Determination of the value of the faraday with a silver-perchloric acid coulometer

Determination of the value of the faraday with a silver-perchloric acid coulometer

Microchemical analysis section:

Resum of values of the Faraday

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