OF ARTS AND BCIEXCES. 116 



faintly violet liquid gives splendid large transparent crystals of phospho- 

 tungstic acid, which are sometimes colorless and sometimes sulphur- 

 yellow. The crystals effloresce with great rapidity, and therefore do 

 not admit of measurement. They appear to be regular octahedra. 

 The solution of the acid is colorless, and has a strongly acid reaction 

 and bitter taste. Of these crystals, — 



1.2791 gr. lost on ignition 0.1809 gr. water = 14.14% 



1.3005 gr. lost on ignition with fused borax 0.1842 gr. water = 14.16% 

 1.4151 gr. gave 1.2130 gr. WO, + P^O^ = 85.72% 



1.5416 gr. gave 1.3201 gr. WO, -f PjO^ = 85.64% 



1.7365 gr. gave 0.0616 gr. Pp-Mg^ = 2.269^ Pp, 



l"Tie analyses lead to the formula 



24 WO3 . P2O5 . 6 H/J + 47 aq, or VT^^'P/^n^^^O)^ + 47 aq, 



which requires : — 



6664 100.00 99.83 



As the phosphoric oxide in the analysis was determined after a single 

 precipitation, a correction of 0.15 is applied to the direct result of the 

 analysis. The crystals had slightly effloresced in drying, which explains 

 the deficiency in the water. 



A quantity of the 18-atom potassium salt 18 WO, . P^O^ . 6 K^O -\- 

 26 aq was dissolved and precipitated by mercurous nitrate. The mer- 

 curous ?alt was then decomposed by dilute chlorhydric acid, and the 

 solution of phospho-tungstic acid obtained evaporated in a flask at 

 about 50^ C. by means of a water air-pump, and then allowed to stand 

 in a partial vacuum over sulphuric acid. After some days splendid col- 

 orless crystals formed, which appeared to be octahedra, but which on 

 standing became columnar in structure, opaque, and yellow. The 

 analyses of these crystals corresponded very closely to the formula 



24 WO3 . P^Oj . 6 HjO + 34 aq, or ^.uPiOn(^^)u + ^^ aq, 

 as the following analyses show: — 



1.4482 gr. lost on ignition 0.1636 gr. water =z 11.30^ 



and gave 0.0492 gr. P.O.Mg, = 2.17% P^O, 



1.5109 gr. lost on ignition 0.1708 gr. water = 11.31% 



and gave 0.0521 gr. P^O-Mg^ = 2.20% PjOj 



