a E. Munroe on the estimation of Phosphoric Acid. 333 



this one the nitro-mercarous phospliate was placed in a mass in 

 the center of the crucible and completely covered with cupric 

 oxide. When the crucible was heated' the cupric phosphate 

 formed coated the outside of tbe pellet and prevented the further 

 escape of the mercurj. This proves the necessity of mixing 

 thoroughly. 



Care should be taken that the mercurous nitrate used is not 

 basic. The salt used in this investigation was prepared in the 

 following way. Pure mercury was dissolved, by aid of gentle 

 heat, in pure nitric acid in a flat, open vessel. More mercury 

 was now added and the whole boiled until every trace of 

 nitrous acid was driven off. The solution was then 'allowed to 

 crystalUze. To the solution formed from these crystals metallic 

 mercury is added to prevent the formation of mercuric nitrate. 

 By this method the salt is obtained perfectly free from mercuric 

 nitrate and the nitrites. 



Ammonio-sodic phosphate. — As the ammonia present decom- 

 poses the mercurous nitrate, it is well to boil with a little 

 caustic soda until it is driven off. In the first analysis magne- 

 sic oxide was substituted for the cupric oxide, but in every 

 other respect the process was the same. 



(1) 1-3500 grms. gave -3991 grms. P^O^ r= 29-56 29'36 ' 



(2) -9832 " " -2902 " " =29-51 " 



(3) 1-0803 « " -3181 " " =29-44 « 



Mean 29-50 



Ammonio-magnesic phosphate. — The solution was freed from 

 ammonia as in the previous case. Bv iffnition the following re- 

 sults were obtained 



(1) -5936 grms. gave -3664 grms, Mff-,P,0, = 43-00 pr. ct. PoO, 

 (•^) -61.35 " "- "4123 " " " ^= 42-99 " " 



Sj the mercurous nitrate process I obtained the following 



(1) 1-0785 gi-ms. gave '4627 grms. = 42-92 pr. ct. F^O^ 



(2) -9500 " " -4084 " =42-98 " 



Mean 42 95 

 Calcic phosphate. — This salt was obtained by precipitating 

 calcic chloride with an excess of disodic phosphate. The pre- 

 cipitate was then carefully washed and dried. This was dis- 

 solved m as little nitric acid as possible. If the solution is too 

 acid the precipitate is not formed until sodic hydrate is added, 

 ^ne nitro-mercurous phosphate was ignited with magnesic 

 oxide. By this means the following results were obtained: 



(1) -6190 grms. gave -1606 grms. P^O^ = 25-94 pr.ct. 



(2) -6765 " « -1755 " '* =25-96 " 



Mean 25-95 



