Resum of values of the Faraday

Abstract

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.

A century and a half of silver-based coulometry

“…The 1968 figure for the Faraday given by Hamer resulted from an examination of values obtained by various methods (28). These were…”

Volt Maintenance at NBS via 2e/h: A New Definition of the NBS Volt

“…By December 1969 the emf's of several cells in the NRG showed large instabilities due to the formation of gas bubbles. I n order to maintain the stability of the legal volt, a new mean for the NRG was calculated (neglecting the unstable cells) using well established procedure [20]. Measurements of the reference cells were made using the "pivot cell" technique whereby all cells are read against only one cell (the pivot or favorite cell).…”

Absolute determination of the electrochemical equivalent and the atomic weight of zinc. I. Method, apparatus, and preliminary experiments

“…are not accurate due to th e variation of the amount of occluded mother liquor in the deposit. This aspect of silver deposition coulom e ters has been di sc ussed by Hamer [18]. A more direct approach to the determination of the electrochemical eq uival ent is through the use of absolute curre nt and time meas ure ment.…”