Oy THE KLECTIiOr^VrrC MKTIKJDS of QlAXTrrATUE ANALYSIS. 173 



Expenment A. 0'2407 gr. of bismuth in solution + ?> gr. of citric acid 

 gave after eighteen hours a fairly firm reguline deposit, which weighed 

 0-2382 gr. 



Experiment B. 0'1805 gr. of bismuth gave under the same conditions 

 a perfectly firm deposit weighing 0'1807 gr. 



Experiment C. 0'1805 gr. of bismuth with 2'5 gr. of citric acid gave 

 an excellent deposit of 0-1804 gr. 



The concentration of the solution in experiment A was too high, as 

 already pointed out ; but the results obtained in the weaker solutions used 

 in B and C were as good as could lie obtained in any determinations of 

 this class. 



The effect of the addition of sulphuric acid is shown in the next three 

 experiments. 



Experiment D. 0'1805 gr. of bismuth in solution with 0"5 c.c. of pure 

 freshly distilled HoSO^ and 2 gr. of citric acid gave, after twenty hours, as 

 good a deposit as in B, and weighed 0"1807 gr. 



Experiment E. 0'1805 gr. bismuth with the same volume of H.jSOj, 

 but with 4 gr. of citric acid. The metal came down very slowly from 

 solution, but in good condition, even when a stronger current was used 

 for a longer time than usual : at the end the weight obtained; after 

 twenty-six hours, was 0'1801 gr. The proportion of citric acid used was 

 therefore needlessly large. 



Experiment F. 0']504 gr. of bismuth in solution, 1 c.c. of H^SO^ and 

 2 gr. of citric acid gave a good deposit, which weighed 0-1507 gr. 



Therefore good results can be obtained in presence of much more free 

 sulphuric and nitric acids than would probably be present in actual 

 analysis, or could be separated from mixed sulphates. 



In the remaining tests cadmium or zinc salts were present. 



Experiment G. 02106 gr. of bismuth in solution, 1 c.c. of 11,80^, 2 gr. 

 of citric acid, and 0-125 gr. of cadmium in the form of sulphate. Result : 

 0-2687 gr. The deposit easily oxidised and contained some cadmium, 

 though the current was kept as low as possible throughout. 



Experiment H. 0-2106 gr. of bismuth in solution, in all respects as last, 

 gave 0-2986 gr. of deposit containing cadmium. 



Experiment I. 0-1805 gr. of bismuth as last, except that only 0-5 c.c. 

 of H2SO4 was added, gave a fair deposit, but contained cadmium and 

 weighed 0-2096 gr. 



Experiment J. 0-1925 gr. bismuth ; treated solution as last, but with 

 4 gr, of citric acid, gave 02340 gr. deposit, easily oxidised as in the other 

 cases, and cadmium was found in the film. 



The results with zinc were similar ; for example : — 



Experiment K. 0-1504 gr. bismuth; the solution containing zinc in 

 the form of sulphate instead of cadmium, O'S c.c. H2SO4 and 2 gr. of 

 citric acid. The metal separated in fair condition, but was easily oxidised ; 

 it weighed 0-1642 gr. and contained traces of zinc. 



Experiment L. 0'1805 gr. bismuth as last, and with zinc sulphate, gave 

 0-1851 gr., and contained zinc also. 



Therefore, while bismuth can be determined electrolytically with 

 accuracy in simple and dilute solutions containing citric acid, and even 

 relatively large proportions of free nitric and sulphuric acidc, we are 

 unable to recommend its electrolytic separation from any of the metals 

 with which we have experimented. 



