RICHARDS AND ROGERS. — ATOMIC WEIGHT OF ZINC. 161 



Gladstone and Hibbert deposited silver in one cell by means of a 

 voltaic current, while zinc was being dissolved from an amalgamated 

 plate in another. Although the experiments are interesting, it would 

 appear from the results of Vanni * and others that the possibility of 

 side reactions makes the strict applications of Faraday's law for the 

 determination of atomic weights of rather doubtful efficacy. One 

 would exi^ect the method adopted to give a result larger than the true 

 one. 



Marignac's work upon the chloride of zinc and the double chloride 

 of zinc and potassium is even less satisfactory than his investigations 

 of other chlorine compounds ; it merits no further notice. 



It is evident from these statements that the three least unsatisfac- 

 tory determinations are all vitiated to a greater or less extent by con- 

 stant errors ; the work of Morse and Burton by one which tends to 

 lower the result ; the work of Gladstone and Hibbert by one which 

 may tend to raise the result ; and the work of Baubigny by two which 

 tend to counteract one another. One would expect the atomic weight 

 of zinc to prove in the end equal to about 65.4. 



It seemed very desirable to obtain a series of determinations which 

 should be wholly different from any of these ; and for this reason 

 zincic bromide was chosen as the starting point of the present re- 

 search. Additional advantages presented by the use of this substance 

 are the fact of its ready and accurate analysis, and the fact that a 

 determination of the ratio 2 Ag : ZnBr, would bring the element into 

 a series of elements which have been determined by Stas and others 

 with great precision in this way. 



* Berichte d. d. Ch. G., XXIV., Ref. 882. 



VOL. XXXI. (n. S. XXIII.) 11 



