76 PROCEEDINGS OP THE AMERICAN ACADEMY 



the analogy which I have shown to exist between VgOj . O3 and 

 WO3 or M0O3, we may perhaps extend the above conclusions to 

 the cases of the tungstates, molybdates, chromates, etc. Thus we 

 may regard KgO . 2 CrOg as the initial term of a series corresjionding 

 to the third series of vanadates. If vs^e double the usual formula of 

 potassic terchromate, and write it 2 K2O . 6 CrOg, we shall have the 

 second term in a series corresponding to that of the metatungstates, 

 the first term being the tetrachromate KgO . 4 CrO^. 



As a further support to my view that the metatungstates form a 

 homologous series, I shall here describe two new tungstates obtained 

 since the first part of this work was published. 



IG : 3 : 4 Sodio-ammonic Tungstate. — I obtained this salt accidentally 

 in attempting to prepare a series of glycero-phospho-tungstates. The 

 thick syrupy liquid obtained by heating pulverized glacial phosphoric 

 acid with glycerine, and allowing the mixture to stand for some days, 

 was neutralized with ammonia and poured into a hot solution of 12:5 

 sodic tungstate. A beautiful white salt, in shimmering talcose scales, 

 separated as the solution cooled. After careful draining, the salt was 

 recrystallized for analysis. The crystals had a fatty lustre, and were 

 quite easily soluble iu hot water. No phosphoric acid could be found 

 in the salt by the most careful testing, and no organic matter. In 

 this salt, 



2.3796 gr. lost on ignition 0.2825 gr. = 11.87 % 



< 2.1691 gr. " " 0.25G8gr. =11.84% 



1 2.1691 gr. gave 1.8209 gr. WO, = 83.94 % 



2.0956 gr. " 0.0973 gr. (NHJ2O = 4.64 % 



The analyses correspond to the formula 



16 WOg . 3 NagO . 4 (NHJ^O + 18 aq. 



4430 100.00 



This salt is especially interesting because it supplies a new term to 

 the series of metatungstates, : — the highest as yet obtained. 



