of Phosphoric Acid. 337 



actions of the most important salts of the metallic oxides with 

 a solution of c-phosphate of soda. 



Sohition of chloride of barium produces a copious precipi- 

 tate, which is neither sohible in excess of the phosphate of 

 soda nor of the chloride of barium. 



Solution of chloride of calcium reacts in the same manner. 

 Traces of the precipitate are soluble in excess of the chloride 

 of calcium, and may be precipitated from the filtered solution 

 by ammonia. 



Its reaction with a solution o^ sulphate of magnesia is known 

 generally, but not perfectly in detail. The sulphate produces 

 a precipitate in a solution of the phosphate of soda, which is 

 insoluble in the latter, but soluble in excess of the solution of 

 sulphate of magnesia. If this clear solution be treated with 

 ammonia, a copious precipitate falls, part of which consists of 

 hydrate of magnesia and is soluble in chloride of ammonium; 

 another portion, which is composed of the phosphate of mag- 

 nesia and ammonia, is insoluble in it. The clear solution of 

 the phosphate of magnesia in the sulphate of magnesia, when 

 boiled, yields a copious precipitate, which however com- 

 pletely disappears as the liquid cools, reappearing if the ebul- 

 lition be repeated. If however this experiment be repeated 

 many times, the precipitate thrown down on ebullition at last 

 ceases to disappear entirely on cooling. 



The precipitate produced by nitrate of silver is insoluble 

 both in excess of the phosphate of soda and in the salt of 

 silver. 



Solution of pernitrate of mercury produces a white precipi- 

 tate, which is not insoluble in excess of the solution of the 

 mercurial salt; but as this always contains free acid, the solu- 

 bility of the precipitate may arise from this. 



Solution of the yrotonitrate of mercury causes a white pre- 

 cipitate, insoluble in excess of the mercurial solution. 



Solution of the bichloride of mercury at first produces no 

 change. After standing for a long period, a slight red de- 

 posit subsides, which is produced sooner and in greater abun- 

 dance by heat. The reaction is the same as with the pyro- 

 phosphate of soda. 



Solution of sulphate of copper produces a bluish-white pre- 

 cipitate, soluble in a large quantity of the cupreous solution. 

 A copious precipitate is produced by heat in the clear solu- 

 tion, which completely disappears on cooling. 



Solution of ihe protosulphate of manganese produces a white 

 precipitate, which is only soluble in a very large excess of the 

 solution of manganese. A precipitate is caused in this solu- 

 tion by ebullition, which completely disappears on cooling. 

 Phil. Mag. S. 3. Vol. 34.. No. 230. May 1849. Z 



