OP ARTS AND SCIENCES. 57 



gradually becomes orange-red, orange, and yellow, and the original 

 salt is finally deiDOsited. The changes of color observed are due to the 

 decomposition of the ammonium salt by water, and the formation of 

 ammonic phosphates and of phospho- vanadates differing in constitution 

 from the original compound and containing a greater proportion of 

 vanadic pentoxide for one molecule of phosphoric oxide. Phosphoric 

 acid is also set free in the reaction. The deep red solution, on stand- 

 ing, deposits beautiful small granular ruby or garnet-red crystals. Of 

 these crystals, 



( 0.3156 gr. lost on ignition (alone) 0.0691 gr. = 21.89% 

 1 0.3 156 gr. gave with KMnO^ 0.2377 gr. = 75.32% 



The analyses correspond with the formula 



20 V2O5 . F.p, . 6 H,0 + 53 aq, 



4864 100.00 



The phosphoric oxide was determined by the difference. The solu- 

 tion of the acid has a dark red color and a strongly acid reaction. It 

 gives cmnani on-colored flocky precipitates with nitrates of silver and 

 thallium. The silver salt is readily decomposed by potassic chloride 

 in presence of a trace of chlorhydric acid, giving a red solution which 

 deposits beautiful square thin tabular crystals, the red color of which is 

 so deep that they appear black by reflected light. In preparing the 

 salts of this series it will probably be best to saturate a small propor- 

 tion of the acid with an alkaline base, and then to add the rest of the 

 acid. For the present the basicity of the acid is undetermined, and 

 the assumption that it contains six molecules of water is merely pro- 

 visional. It also appears probable that salts of this and similar higher 

 series may be prepared by mi.xiiig solutions of alkaline metavaiiadates 

 with those of alkaline phosphates in definite proportions, and then 

 adding dilute sulphuric acid in small portions at a time, stirring or 

 shaking after each addition of acid. The precise quantity of acid to be 

 added should be calculated beforehand, which may of course be easily 

 done if we assume a definite basicity, as, for instance, that each mole- 

 cule of salt shall contain three molecules of fixed base. 



