196 On Tribasic Phosphoric Acid. 



and ammonia was added t<» alkaline reaction. A slight pre- 

 cipitate was filtered off, washed out, dissolved in nitric 

 acid, and precipitated by molybdic acid solution. The small. 

 yellow precipitate was dissolved in ammonia after washing. 

 This Bolution was added to the main one, containing the 

 phosphoric acid. After evaporation to the required volume, 

 PO was precipitated by magnesia mixture. The fluid til- 

 tered from the yellow precipitate was treated in a proper 

 manner, and the slight amount of alumina weighed. The 

 insoluble residue that had been freed from PO, by washing 

 was separated from SiO a in the usual way. and the Al, (>. pre- 

 cipitated and weighed. Results are as follow- : 

 (a) L.027 (1>) 1.032 (c) L.03 



PO, 32.31 32.28 32.35 



a , lM1M _l < -»-«»4+ -M...U+ IQO1-19-07+ 



A1 - '••'• 0.15 ' A 0.14 ■•'-•- ou 



ttO 4-.:." 48.54 48.44 



mean PO 32.31 

 Al.n. L9.19 

 IK) 48.50 



111. Method with SiO, (Fuchs' water-glass). 



The analyses were made in the manner heretofore described, 

 hut the tli i id containing the phosphoric acid, after having 6epa- 

 rated si i » .. and boiled with a little concentrated HO, SO,, w as 

 mixed with PbO,NO„and then precipitated bj Nil and Mlo, 

 I i < . The precipitate was filtered elf and washed out ; the ni- 

 trate < tained no trace of P< >,. The precipitate was dissoh ed 



in a I in le ll< >. \'< ) . diluted with ll< >. and the had separated 



by 11^. After < pletely washing out, evaporating and filter* 



from separated sulphur, ammonia and (disregarding a very 

 slight precipitate) magnesia mixture was added. 



1 ■ • operation with lead was interpolated \<< gel rid <>i the 

 Large amount of alkaline salt.-, that exert a dissolving influence 



