268 Flora — Estimation of Cadmium taken as the Sulphate. 



Art. XXIX. — The Use of the Rotating Cathode for the Esti- 

 mation of Cadmium taken as the Sulphate; by Charles 

 P. Flora. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — cxxxix.] 



In a recent paper from this laboratory* has been described 

 the application of the rotating cathode to the rapid estimation 

 of copper, silver and nickel ; and, in a later paper, f its fitness 

 for the estimation of cadmium as well as several other metals 

 has been shown. The object of the present investigation has 

 been to more thoroughly study the conditions under which 

 cadmium may be estimated by this means. The apparatus 

 used was that described in the previous papers. Since it had 

 already been shown + that cadmium taken in the form of the 

 sulphate can be estimated by deposition of a solution slightly 

 acidulated with sulphuric acid, this formed the natural point 

 of departure. 



I. In Solutions containing Sulphuric Acid. 

 A solution of cadmium sulphate was prepared, containing 

 approximately 16*6 grams of the salt to the liter of water. 

 Portions of this solution were carefully measured from a 

 burette, diluted to the desired volume, a few drops of dilute 

 sulphuric acid (1:4) added, the proper connections made and 

 the electrolysis conducted as previously described. The fol- 

 lowing were the results obtained upon two different solutions : 











Solution A. 









No. 



Sol. 



H 2 S0 4 . 





Cur't 





E.M.F. 



Cd. 



of 



taken. 



(1:4) 



Time. 



read. = 



N.D.Voo 



approx. 



found 



Exp. 



cm 3 . 



drops. 



min. 



amp. 



amp. 



volts. 



grm. 



1. 



15 



5 



18 



O'4-l-O 



1-2-3-0 



8 



0-1111 



2. 



15 



5 



10 



0*4-0-5 



1-2-1-5 



8 



0*1090 



3. 



15 



5 



16 



0-4-0-9 



1-2-2-7 



8 



0-1115 



4. 



15 



7 



35 



0-5-1-0 



1-5-3-0 



8 



0-1117 



5. 



15 



12 



25 



1-0-1-5 



3-0-4-5 



8 



0-1115 



6. 



15 



10 



35 



1-0-1-5 



3-0-4-5 



8 



0-1120 



7. 



15 



18 



30 



1-5-2-0 



4-5-6-0 



8 



0-1119 



8. 



15 



15 



25 



1-5-2-0 



4-5-6-0 



8 



0-1117 



9. 



30 



Indef. 



15 



3-0-4-0 



9-0-12-0 



8 



0-2235 



10. 



20 



12 



35 



2 0-3-0 



6-0-9-0 



8 



0-1491 



11. 



15 



Indef. 



60 



2-0 



6-0 



8 



0-1120 



In experiments numbered 1 to 4, the liquid at the end of 

 the period indicated showed traces of cadmium remaining, but 

 in the seven experiments following these the cadmium was all 

 deposited upon the cathode in a satisfactory condition. These 



* Gooch and Medway, this Journal [4], 320 (1903). 



f Medway, . is Journal [4], xviii, 56 (1904). % Loc. cit. 



