ls»; On Tribasic Phosphoric Acid. 



Btilphide of ammonium, the operation was repeated in the 

 Bame manner, the Biilpliide of iron having been previously 

 dissolved in hydrochloric acid. The Becond filtrate contained 

 no trace of phosphoric acid, the Bulphide of iron was then dis- 

 solved in IK'l. oxydized with ll< >. N< • . filtered from the sepa- 

 rated S, precipitated by XII. ami carefully washed out. It 

 was weighed after drying and igniting. The filtrate contain- 

 ing the phosphoric acid was evaporated to a suitable volume, 

 slightly acidulated, filtered from separated sulphur, and pre- 

 cipitated by magnesia mixture, in the usual way. This 

 method will yield better results than the ordinary method of 

 fusing with carbonate and nitrate of soda. Yel all phosphoric 

 acid cannot even here he separated from the iron, and while in 

 the method by fusion ahout 1..". p. c. (respectively 1 p. c.) of 

 phosphoric acid will remain with the iron, not to mention that 

 part of the phosphoric acid, which, in the latter case, is dis- 

 solved a- ammonio-phosphate of magnesia in the alkaline sahs, 

 hei-e 0.7 ]». c. will he found to !,(• missing. This deficiency of 

 phosphoric acid we onghl to find in an increase of the weight 

 of the iron, bill instead of this, we have still less, owing, in 

 in\ opinion, to the Bulphide of iron being soluble in poly- 

 Biilphide of ammonium, under the influence perhaps of the 

 remaining phosphoric acid. 



[I is a well-known fact, that Bulphide of iron will dissolve in 

 poly-sulphide of potassium ami sodium to a larger extent in 

 hot than in cold solutions. Am! now we cannot hut consider 



this to he also the case with Bulphide of ammonium. Ii i^ lost 

 to the analysis probably in this way. 



In evaporating the alkaline Bolution of sulphide of ammo- 

 nium containing the phosphoric acid, it separates in Buch a 



fonn. and i- covered with the separated sulphur in such a way 

 to he not easily attacked by dilute hydrochloric ;icid. A.8 a 



method it is nice and clean, the results being as follow.- : j 



