a E. Munroe on the estimation of Phosphoric Acid. 335 



ferric was reduced to tlie ferrous salt by the addition of me- 

 tallic iron, by passing a stream of sulphydric acid through the 

 solution, and by the addition of sulphurous acid, but without 

 better results. The phosphate was dissolved in potassic cyanide 

 and the ammonio-magnesian solution added to precipitate the 

 phosphoric acid. I boped that potassic ferrocyanide would be 

 formed which would remain in solution and allow the phosphoric 

 acid to combine with the potassium. The experiment, however, 

 proved unsuccessful, and with these results the further investi- 

 gation of ferric phosphate was suspended. 



Although the ignition with cupric oxide leaves nothing to 

 be desired in point of accuracy, and is a much quicker method 

 than any now in use, yet it was thought that some other agent 

 might be employed which would hasten the process still more. 



Stannic oxide was tried for this purpose. To a weighed 

 quantity of pure tin* the nitro-mercurous phosphate was added, 

 then sufficient nitric acid, sp. gr. IITO, was poured upon tlic 

 mass to oxidize the tin completely. The whole was evaporated 

 to dryness on a radiator, ignited and weighed. The plan 

 seemed very promisino-, but the results, from some unknown 

 cause, were far from being satisilictory. 



Another idea was to fuse the nitro-mercurous phospliate witii 

 some substance which had a low fusing point, so that tlie mcT- 

 cury might Ije volatilized, the phosphoric oxide ]-emanini,--. 

 Accordiuglv it was fused with free sulphur but some of tlie 

 phosphoric 'oxide was always volatilized. Potassic dichroraate 

 and plumbic chromate were both subjected to trial, but as the 

 results were very unsatisfoctory, further investigation in this 

 direction was ab:indoned. 



These results prove couclu 

 the estimation of phosphoric 

 lerricf and uranic phosphatet 



lue lea^t possible quantity of water and add an 

 causes tlie double chloride to crystallize out imi 

 recrystallization from acid solutions. Dry the s 

 equal weight of a mixture of one part of potassi, 

 foun? '" "" P°'^^^^^^ ^""^'^^^^^ 0° ^'°°^^° "" ^""^ 

 obtabed J.™P^^®' ''' *^ "^^''^ °^ ^^'^^ ^^°ls«oh 

 precipitate witli th? anmoib-mngnesian^Solution 

 separation. 



Otto's process of precipitating the phosphoric! 

 Pbate in the presence of tartaril acid was modifl< 

 phosphate was prepared by precipitating lernc 



