OP ARTS AND SCIENCES. 129 



The corresponding formula is 



18 W0 3 . P 2 5 . 6 K 2 + 30 aq, 



5424.4 100.00 



The prismatic and granular salts, therefore, only differ in water of 

 crystallization. It must be remarked, however, that the corrected 

 percentages of the phosphoric oxide in the analyses of the granular 

 salt are too low, which is unusual. 



18:1 Acid Potassium Salt. — When the normal salt is dissolved in 

 water and chlorhydric acid is added in excess, a White crystalline 

 precipitate is formed, which is but very sparingly soluble in water. 

 Of this salt,— 



1.2955 gr. gave 1.1828 gr. W0 3 + P 2 O s = 91.30% 



1.3200 gr. " 1.1994 gr. " =90.86% 



1.1390 gr. « 0.0592 gr. P 2 O r Mg 2 = 3.32% P 2 5 



1.5900 gr. " 0.0817 gr. " = 3.29% " 



1.5225 gr. lost on ignition 0.1087 gr. water == 7.14% 



1.1966 gr. " " 0.0856 gr. " = 7.16% 



These analyses corrrespond to the formula 



18 WG 3 . P 2 O s . K,0 . 5 H 2 + 14 aq. 



Calc'd. Mean. 



4754.4 100.00 100.00 



Ammonium Salt. — The ammonium salt of the 18 atom series may 

 be prepared in the manner given above for the normal potassic com- 

 pound. When amnionic acetate and alcohol are mixed with a concen- 

 trated solution of the sodium salt, no precipitate is formed at first, but 

 after some hours a mass of white crystals is thrown down. After 

 washing with alcohol and re-solution, crystals may sometimes be ob- 

 tained, but the salt usually forms a nearly colorless gummy mass. In 

 this case white opaque crystals separate from a thick and sirupy 



vol. xvi. (n. s. viii.) 9 



