ON THE ELECTROLYTIC METHODS OF QUANTITATIVE ANALYSIS. 297 



II. — Deposition of Zinc frovx Solution of Double Oxalate. 



In 1881 Classen, and also Reinhardt and Ihle, suggested the addition 

 of potassium or ammonium oxalate, or of both oxalates, to the zinc salt. 

 The electrolysis is carried on at the ordinary temperature. 



The method yields good results when the quantity of zinc does not 

 exceed 0*2 grme. ; when larger quantities of zinc are taken the deposit 

 is liable to be dull and spongy instead of firm and bright. 



In experiments 1, 2, 3 and 12 the zinc salt dissolved in water was 

 poured into a hot solution of potassium oxalate (8 grme.) ; in 4 and 5 

 ammonium oxalate (8 grme.) was substituted for the potassium salt ; 

 and in experiments 6 to 11 a mixture of potassium oxalate (6 grme.) 

 and ammonium oxalate (2 grme.) was used. This mixture gave the 

 best results. 



III. — Deposition of Zinc from, Solution of Alkaline Oxalate 



and Sulphate. 



The addition of potassium sulphate (3 grme.) to the potassium 

 oxalate (4 grme.), as recommended by Miller and Kiliani, does not 

 appear to improve the process. 



Experi- 

 ment 



1 

 2 

 3 

 4 

 5 



Zinc taken : 

 grme. 



0-2044 

 01051 

 0-0732 

 0-2729 

 00740 



Zinc found : 

 grme. 



0-2032 

 0-1047 

 0-0733 

 0-2726 

 00734 



C-D-ioo 

 Amperes 



0-4 



0-14 



0-17 



0-28 



0-2 



Remarks 



Black spots 

 Bright 



Black spots 

 Bright 

 Bright 



The zinc is deposited as a bright, firmly-adhering film, occasionally 

 marked by black spots. Classen quotes experiments in the fourth edition 

 of his ' Quantitative Analyse durch Elektrolyse ' showing that this method 

 yields low results. 



IV. — Depositio7i from Hot Solution of Alkali Oxalate in Presence of 



Tartaric Acid. 



The solution of zinc sulphate is mixed with 4 grme. of potassium or 

 ammonium oxalate, diluted with water, and electrolysed at a temperature of 



