OF ARTS AND SCIENCES. 67 



it is much more probable that the acid really contains an atom less of 

 water, and that its formula, apart from the question of basicity, is 



24 Mo0 3 . P 2 5 . 6 H -4- 55 aq, 

 like 



24 W0 3 . P 2 5 . 6 H,0 -f 55 aq, 



already described. This formula requires 23.38% water, instead of 

 23.75%, as found. Debray found 23.40%. As already stated, the 

 crystals analyzed were dried by pressure with woollen pane]-, after 

 draining off a syrupy mother liquor, and may therefore not have been 

 perfectly free from extraneous water. Finally, the analyses of Finke- 

 ner led also to the formula with 61 atoms of water, and I shall adopt 

 this as the definite constitution of the octahedral hydrate. Finkener's 

 work has not yet been published iu detail ; but from the abstract which 

 he has given, it clearly appears that we owe to him the establishment 

 of the true constitution of the only phospho-molyhdie add yet obtained. 

 As already mentioned, there are two other hydrates of pkospho-tung- 

 stic acid, having, respectively, the formulas 



24 W0 3 . P 2 O fi . 6 II 2 -f 47 aq, 

 and 



24 WO a . PX)-, • 6 IFO + 34 aq. 



The two hydrates of phospho-molybdic acid described by Debray 

 would correspond to the formulas 



2 1 Mo0 8 . P 2 0, . 6 H 2 -f 24 aq, 

 and 



24 MoOg . P a O s . 6 H 2 -f 43 aq, 



if we suppose them, as is most probable, to belong to the 24-atom se- 

 ries. The first formula requires 13.05%, the second 19.66% water; 

 Debray found 13.09 % and 19.60 %. Finkener obtained still another 

 hydrate, containing about 32 atoms of water, basic water included. 



Phospho-molybdic acid dissolves very readily in water, forming a 

 colorless liquid which has a strong acid reaction. As already stated, 

 the solution is always accompanied by a slight decomposition, with for- 

 mation of a very pale greenish white crystalline substance. A pre- 

 cisely similar decomposition is observed in the solution of the corre- 

 sponding phospho-tungstic acid. The crystals lose all their water when 

 slightly ignited. According to Finkener, three atoms of water remain 

 at 140° C. The solution readily expels carbonic dioxide from the 

 alkaline carbonates. The question of the basicity of the acid will be 

 discussed farther on. 



