2S8 



SUPERPHOSPHATE OF POTASH. 



^ XVIII. 



Experiments on the acid Phosphate of Potash : fty Mr. 

 Vauquelin*. 



Crystallizable XVJL K', Vitalis, secretary to the academy of sciences, letters, 

 *^aS"o"Hc°^ and arts at Rouen, and professor of chemistry in that city, 

 acid and |,ot. having formed, in the course of his operations, a compound 

 **^* of phosphoric acid and pota>>h, each extrenaely pure; and 



having obtained, by suitable evaporation, a perfectly crys- 

 tallized salt; presumed that other chemists, who have all 

 announced the uncrystalhzability of phosphate of potash, 

 were deceived. 



Too modest to take on himself to contradict what had 

 been said on this head by the ablest chemists, he sent me a 

 small quantity of the salt, that 1 might examine it, and give 

 him my opinion of it. The following are the results of ray 

 researches. 

 |te prpperdes. ^' This salt is very white, crystallized in prisms with four 

 equal sides, and terminated b, pyramids with four facescor* 

 responding to the sides of the prism. 



2. It has a very sour taste, and powerfully reddens in- 

 fusion of litmus. It is not alterable by the air. 



3. With lime-water it throws down a copious, white, floe- 

 culent, and as it were gelatinous precipitate. 



4. Caustic potash evolves from it no ammonia. 



5. It forms a copious precipitate with solution of muriate 

 of platina. 



6. It gives out no phosphorus by the action of heat, but it 

 melts into a clear glass, which crystallizes and becomes opake 

 en cooling. 



7., After having been thus melted, it does not dissolve in 

 water so easily as before. 

 Uncrystallua- 8. A portion of this salt having been saturated with pot- 

 bie when neu- ash, and subjected to spontaneous evaporation, did not crys- 

 tallize: it was reduced to a kind of viscous liquor, resem- 

 bling a solution of gum. 

 A superplios- From these experiments it evidently follows, that the salt 

 •sh^'^^^ ^^'* in questiovi is an add phosphate of potash; consequently, 



• Ann. de Chim. tol. LXXIV, Apiil, 1810, p. 96. 



that 



