OP ARTS AND SCIENCES. 269 



The solution of this salt gives a beautiful scarlet precipitate with 

 argentic nitrate, and a fine yellow precipit;ite with salts of strychnin, 

 which after standing some hours becomes granular crystalline. 



12 : 2 : 3 (?) Vanadlo-vanadlco-tungslate of Stiver. — The salt an- 

 alyzed was in beautiful scarlet crystals, and was prepared by precipi- 

 tating the ammonium salt with argentic nitrate, and washing with 

 cold water. The salt is not distinctly crystalline Avhen first thrown 

 down, but becomes so after standing in the liquid. It is very slightly 

 soluble in cold water, but dissolves in much hot water to a yellow 

 liquid. Of this salt, — 



2.11 93 gr. lost on ignition 0.0621 gr. = 2.93% 

 0.7511 gr. gave 0.7420 gr. AgCl = 28.21% Ag.p 



These analyses agree with the formula, 



12 WO3 . 2 V2O5 . 3 VO, . 6 Ag, + 8 aq, 



which requires : — 



4935 100.00 



The analyses which I have given may not be considered as suffi- 

 ciently complete to establish the formulas assigned, but they serve to 

 prove the existence of at least one class of vanadio-vanadico-tungstates. 

 In substances of such high molecular weights the agreement between 

 the formulas of three different salts prepared under precisely the same 

 conditions has a certain value, but it is less conclusive than when 

 the molecular weight is lower, because such a change as is produced 

 by writing, for instance, 2 VO.^ for VgO-? f'o^s not greatly affect the 

 percentage results. If we admit the correctness of the formulas given, 

 it will still be necessary to double them in order to construct a structu- 

 ral formula which shall be symmetrical, since the number of molecules 

 of VOg, either free or contained in V2O-, is uneven. For the complete 

 analysis of compounds of this class it will be most advantageous to de- 

 termine the vanadic pentoxide by heating with strong chlorhydric acid 

 in the manner already indicated, and then to determine the dioxide in 

 another portion by means of hypermanganate, if possible, or by first 



