120 PROCEEDINGS OF THE AMERICAN ACADEMY 



24 : 3 Acid Potassium Salt. — When a solution of the 24 : 2 acid 

 sodic salt is added to one of a salt of potassium, a heavy ^vhite crystal- 

 line very slightly soluble precipitate is formed, either immediately or 

 after a short time. The salt forms very small granular crystals. It 

 requires a large quantity of water for solution, a white much more 

 insoluble salt being formed in small quantity by the action of water, 

 so that the liquid is, and for a long time remains, milky. It is best, 

 therefore, simply to wash the precipitate with cold water until this 

 begins to give a turbid filtrate, and then to dry the salt by pressure 

 with woollen paper. The salt is also formed when chlorhydric or nitric 

 acid is added to a solution of potassic phosphate and tung^tate in the 

 proportion of 2 molecules of the former to 24 molecules of the latter, 

 — the two solutions being previously boiled together for some time in 

 a platinum vessel. The reaction in this latter case may be expressed 

 by the equation 



24 WO.K, + 2 PO.KH^ + 44 HCl = 24 WO3 . P.O^ . 3 K,0 + 



44 KCl + 24 aq, 

 and in the. case of precipitation by the acid sodium salt, by the equation 



24 WOg . P,03 . 2 Na.,0 . 4 H,0 + 6 KNO3 = 24 WO3 . P.O^ . 3 K,0 . 

 3 H,0 + 4 XaNO. + 2 XO.H -[- 3H2O. ' 



In this salt, — 

 1.1478 gr. gave 1.0588 gr. WO3 + P^g =92.25^ 



1.1764 gr. •' 0.0468 gr. PA^ga = 2.049^ P^ 



1.7383 gr. lost on ignition 0.0576 gr. water = 3.31 r^ 



1.7638 gr. " " 0.0578 gr. " = 3.28% 



The analyses lead to the formula 



24 WO3 . P.,0, . 3 K,0 . 3 H2O + 8 aq. 



6191 100.00 100.00 

 n another preparation of the same salt, — 



0.7340 gr. gave 0.6660 gr. ^0^ -f- P,,0, = 90.74^^ 



1.1400 gr. " 1.0317 gr. " = 90.50% 



0.8028 gr. " 0.0310 gr. P20-^g2 = 2.47% P^Og 



1.5568 gr. lost on ignition 0.0805 gr. water = 5.17% 



0.8822 gr. " " 0.0455 gr. " =5.16% 



