and its Separation from Arsenic. 315 



(8) Distilled water __ .Reported no Ge. No 



cloudiness. 



(9) 0-1 grm. As^Og + 0*0001 Ge Reported Ge present. 



Good test. 



(10) 0*2 grm. SnCl Reported no Ge. Faintly 



cloudy. No ppt. 



(11) 0-0001 grm. Ge Reported Ge present. 



Good test. 



(12) 0*2 grm. ASjOg Reported possible trace 



of Ge very faint. 



In all of these tests potassium permanganate was added with 

 the hydrochloric acid before distilling, to provide the chlorine 

 necessary to prevent reduction and distillation of AsClg in the 

 event of the presence of arsenic. Blanks were made with 

 KMnO^ to determine whether the chlorine evolved would 

 cause a precipitate of sulphur in the distillate when hydrogen 

 sulphide was added. The results of these determinations 

 showed in only a few cases a faint cloudiness, probably due to 

 sulphur, but in no case did a precipitate settle as in experi- 

 ments where O'OOOl grm. Ge was present. Experiments (2), (4), 

 (6), (8), (10) and (12) also showed that the use of potassium 

 permanganate does not vitiate the germanium test. The dis- 

 tillates in Experiments (2) and (4) w^ere allowed to stand over 

 night after saturation with hydrogen sulphide without any pre- 

 cipitate separating from the very faintly cloudy solution. 



Winkler* recommends the following method for the separa- 

 tion of germanium from arsenic. The sulpho salts formed by 

 fusing the mineral containing the elements with sodium carbon- 

 ate and sulphur are dissolved in water, and the solution is care- 

 fully neutralized with sulphuric acid, when the sulphide of 

 arsenic is precipitated leaving the germanium in solution. By 

 treatment of this solution with hydrochloric acid and addition 

 of hydrogen sulphide the germanium sulphide is thrown down. 



Two modifications of this method were tried by us to bring 

 about this separation. First, a solution of the sulpho salts was 

 saturated with carbon dioxide. This treatment caused the pre- 

 cipitation of from 60 per cent to 75 per cent of the arsenic, 

 while no germanium was precipitated. Second, a solution of 

 the sulpho salts was treated with ammonium acetate, acidified 

 with acetic acid, and then treated with hjdrogen sulphide. 

 Under these conditions the arsenic was completely precipitated, 

 and the germanium remained in solution. This process was 

 tried on solutions containing arsenic only and germanium only, 

 as well as upon mixtures, with equal success. Finally, some 

 solutions of content unknown to the experimenter were pre- 

 pared by one of us, and the report by the other showed the 

 accuracy of the method. 



*.Tourn. prakt. Chem., xxxiv, 177; xxxvi, 177, June, 1917. 



