A. A. Ramsay 



This powder was shown to consist of : 



293 



In the first extraction the phosphate experimented with appears to 

 have gone into solution as a mixture of di- and tricalcium phosphate, 

 the dicalcic phosphate predominating. 



In the second extraction the hme and phosphoric acid found indicate 

 a dicalcic phosphate, with very minute quantities of tricalcic phosphate. 



When di-barium phosphate is dissolved in hydrochloric acid, barium 

 chloride and free phosphoric acid are first produced in accordance with 

 the equation BaHP04 + 2HC1 = BaClg + H3PO4. According to Newth^ 

 the addition of an alkali causes precipitation of the phosphate un- 

 changed. The reaction proceeds in two stages — (1) the alkali added 

 (say NaOH) reacts with the free H3PO4 forming sodium phosphate, and 

 (2) the sodium of the sodium phosphate takes the chlorine from the 

 barium chloride, and the barium of the barium chloride unites with 

 the phosphoric acid of the sodium phosphate. These reactions are 

 represented by the following equations : 



BaCl2-fH3P04-f2NaOH = BaCl2 + Na2HPOi-^2H,0 (1), 



BaCl2 + 2Na2HP04-l-2H20=BaHP04H-2NaCl + 2H20 (2). 



The solution of tricalcic phosphate in acid and its precipitation by 

 an alkali has not been discussed in any text-book or paper that I have 

 had access to, but the following reactions suggest themselves as such 

 as would occur. 



Solution in hydrochloric acid would be represented by the equation 



^ Newth, Manual of Chemical Analysis, p. 64. 

 Journ. of Agric. Sci. viii 



20 



