OF ARTS AND SCIENCES. Ill 



8491 100.00 



All the compounds of this group which I have obtained belong, as 

 will be seen, to the same type which contains the frequently recurring 

 chemical mass of twenty-two molecules of tungstic oxide, united to 

 nine molecules of pyrophosphoric acid or a pyrophosphate, together 

 with a certain amount of base over and above that required to saturate 

 the phosphoric oxide. We mny represent this group provisionally by 

 a structural formula containing nine groups of the form : 



HO I I OH 



\ ro _ o — OP ( 



HO ''^ I 1 ^ OH 



Further investigation will doubtless show that there are other series 

 of pyrophospho-tung'itates and analogous pyrophospho-molybdates. It 

 is especially desirable to study the compounds which remain in solution 

 after the precipitation of part of the pyrophosphoric oxide by means 

 of cupric sulphate. 



It may here be remarked, that Wallroth * has described a series of 

 pyrophosphates which contain nine molecules of P.,0- , united in each 

 case to thirty-six atoms of metal. Thus we have 



Cajo Na,y (PoO^)^ 

 Mg,„ Na„ (PA)o 

 Co,„ Na,„(PA), 

 N,„ Na,„(PA),. 



It would therefore appear that similar complex molecules enter 

 directly into combination with twenty-two molecules of tungstic oxide, 

 but tliat the complexity is not necessarily due to a determining action 

 on the part of the latter. 



* Bull, de la Soc. Cliimique, [2,] xxxix. 81G. 



