268 A GENERAL FORMULA FOR THE 



base, it is probably unexceptionable. It does not, however, 

 altogether accord with the object of the present formula. The 

 soda of the phosphate of soda serves to neutralize the muriatic 

 acid of the muriate of magnesia ; a quantity of muriate of soda 

 is of course formed, which remains with the muriate of soda of 

 the water, and the amount of which, therefore, it is necessary 

 to determine with accuracy. This may be done from the 

 quantity of phosphate of magnesia obtained giving the equiva- 

 lent portion of muriate of soda, either by means of the equiva- 

 lents of the acids, or of the bases. But still this renders the 

 method somewhat complicated ; and it may be liable to some 

 error, if any excess of phosphate of soda be added, which, in 

 ■order to precipitate the magnesia entirely, it may be difficult 

 to avoid ; this excess remaining with the muriate of soda, and 

 rendering the estimate of it incorrect. And independent of 

 these circumstances, it would be preferable to give uniformity 

 to the operation, by employing some method by which the 

 product in this, as well as in the previous steps, is removed, at 

 the end of the analysis, leaving only the muriate of soda. 



It seemed probable that this might be attained, by employ- 

 ing phosphoric acid with the carbonate of ammonia, to form 

 the triple phosphate of ammonia and magnesia, such an excess 

 of ammonia being used, as should both be sufficient for the 

 constitution of this compound, and for the neutralization of the 

 muriatic acid of the muriate of magnesia ; muriate of ammo- 

 nia would thus be substituted, the same as in the preceding 

 step of precipitating the lime, which at the end would be ex- 

 pelled by heat, leaving muriate of soda alone. I accordingly 

 found, that when this variation of the process was employed, 

 the clear liquor, after the precipitation, was not affected by the 

 addition either of phosphate of soda with ammonia, or of sub- 

 carbonate of soda, — a proof that the separation of the magnesia 



had 



