Flora — Estimation of Cadmium taken as the Chloride. 393 



it was found to be absolutely unfitted for the estimation of 

 cadmium when taken as the chloride. The deposited metal 

 was always spongy, often non-adherent and unfitted for quan- 

 titative work. The sponginess was less marked when no potas- 

 sium sulphate was present, but the metal was still poorly 

 adherent and nnweighable. The modifications tried are given 

 for the sake of comparison in the following table. The cur- 

 rent potential throughout was 7*8 volts, while the dilution, 

 excepting in experiment No. 4, was 45 cm3 . In No. 4 a dilution 

 of 65 cm3 was tried, but it offered no apparent advantage. 





Od. 



NaOC 2 H 3 0. 



K 2 S0 4 . 



Our't= 



N.D 100 



Time. 





N 



3. grai. 



grm. 



grm. 



amp. 



amp. 



min. 



Notes. 



1. 



0-1324 



1-5 



0-5 



1-5 



4-5 



13 



very spongy 



2 



0-1324 



1-5 



none 



1-0 



3-0 



8 



0-1314 grm. fd. 



3. 



0-1059 



1-0 



a 



0-75 



2-25 



20 



non-adherent. 



4. 



0-1059 



1-5 



0-5 



1-5 



4-5 



— 



j spongy, non- 

 ( adherent 



5. 



6. 



0-1059 

 0-1059 



1-5 

 1-5 



none 



1-0 

 0-75 



3-0 

 225 



— 



( 2 cm3 formalin 

 ( added, spongy 

 non-adht., cryst. 



7. 



0-1059 



0-5 



0-5 



1-0 



3-0 



— 



a a 



III. In Solutions containing Cyanides. 



The use of a cyanide solution gave results with the chloride 

 of cadmium as satisfactory as were given when the sulphate of 

 cadmium was taken. As in that case, care must be taken to 

 avoid foaming of the solution. The best dilution seemed to be 

 6 5 cm3 . The time required is a trifle longer than in the estima- 

 tion of cadmium sulphate by this method. The following 

 results were obtained : 



No. Cd. KCN. NaOH. Curt = N. D 100 E.M.F. Time. Cd. fd. Error, 

 grm. grm. grm. amp. amp. vts. min. grm. grm. 



1. 0-1324 1-5 TO 4 12 7'8 35 0-1322 —0*0002 



2. 0-1324 1-5 1-0 4 12 7"8 40 0'13l7 — 0'0007 



In experiment No. 2 there was much foaming, and a trace 

 of cadmium remained in solution, the deposition being much 

 retarded. 



IV. In Solutions containing Pyrophosphates. 



The different modifications of the pyrophosphate method 

 gave results which were quite satisfactory, and in every 

 respect comparable with the results obtained with this elec- 

 trolyte in the estimation of cadmium sulphate. As was the 

 case with that salt, the use of ammonium hydroxide to dis- 

 solve the precipitate gave the most satisfactory results ; while 

 after that, sulphuric acid seemed to be the most suitable 



