120 PROCEEDINGS OP 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 white 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 tungstate 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 W0 4 K 2 + 2 P0 4 KH 2 -4- 44 HC1 === 24 W0 3 . P 2 5 . 3 K 2 -f 



"44 KC1 -4- 24 aq, 

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



24 AVO3 . P 8 0. . 2 Na 2 . 4 H,0 + 6 KN0 3 = 24 W0 3 . P 2 5 . 3 K 2 . 

 * 3 H 2 4- 4 NaN0 8 + 2 N0 8 H + 3H 2 0. 



In this salt, — 

 1.1478 gr. gave 1.0588 gr. WO, -f P 2 6 =92.25% 



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



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



