106 PROCEEDINGS OF THE AMERICAN ACADEMY 



and when raolybdic oxide is digested with a solution of an alkaline 

 antimonute. 



Analytical Methods. — The separation of an.imony from molyb- 

 denum cannot be effected by sulphydric acid, because molybdic sul- 

 phide is always precipitated in greater or less quantity, even when 

 phosphoric acid is present in the solution. The only method which I 

 have been able to devise consists in fusing the salt to be analyzed or 

 the mixture of oxides with potassic cjanide, as in the case of the 

 separation of antimony from tungsten. In this case also it is always 

 advisable, and sometimes necessaiy, to add a sufficient quantity of an 

 alkaline carbonate to form a mixture of neutral molybdate and anti- 

 monate, as suggested by Mr. Herman Schmidt. AVith proper care 

 the two oxides may be precipitated together by mercurous nitrate 

 and mercuric oxide, and ignited without sensible loss of molybdic 

 oxide ; but there is then always a certain amount of reduced metal- 

 lic antimony present, and on the whole the method is not to be 

 recommended. 



7:3:5 Amnionic Antimonio-molyhdate. — Antimonic hydrate dis- 

 solves readily on boiling with a strong solution of 14:6 ammonic 

 molybdate. The hydrate should be in excess, and should be added in 

 small portions at a time, until, after long boiling, a part remains undis- 

 solved. After standing twenty-four hours, beautiful colorless crystals 

 are deposited in quantity. These have a nacreous lustre, and are 

 readily soluble in hot watei\ In this salt, 



1.0647 gr. lost on ignition with W04Na2 0.20,32 gr. = 19.55 p^ 

 1.2234 gr. gave 0.2418 gr. NH.Cl = 9.60 % (NH4)20 



0.9576 gr. " with KCy 0.3321 gr. Sb = 46.24 % SbnO.. 



The analyses correspond with the formula 



7 M0O3 . 4 Sb^O^ . 5 (NIl4)oO + 12 aq, 



which requires : 



Calc'd. Found. 



7 M0O3 1008 36.47 36.52 



4 SbaO. 1280 46.31 46.24 



5 (NH^jO 260 9.40 9.60 

 12 HoO 216 7.82 7.64 



2764 100.00 



The formula may also be written 



7 M0O3 • 8 SbO^NH^ . (NII,)oO + 12 aq. 



