PHOSPHATES. 351 



Before decomposition. After decomposition. 



Phosphateof/ 2 ^ d . a ' - -72 nitrate of soda 



soda 1 Water -^ ^nitrate of water 



I Phosphoric acid 

 3 Nitrate of f 2 Nitric acid . . . 

 Nitric acid . 



7 



silver "S 



3 Oxide of silver -A Phosphate of silver 



(Tribasic phosph. silv.) 



Here, then, is exact mutual decomposition, but it is attended 

 with a phenomenon which does not occur when other neutral 

 salts decompose each other. The liquid does not remain 

 neutral, but becomes highly acid after precipitation ; the reason 

 is, that one of the new products is the nitrate of water, or 

 hydrated nitric acid ; and consequently the products, although 

 neutral in composition, are not neutral to test paper. 



The pyrophosphate of soda, which is bibasic, decomposes, on 

 the other hand, two proportions of nitrate of silver, and gn r es a 

 pyrophosphate or bibasic phosphate of ilver, which is a white 

 precipitate; thus 



Before decomposition. After decomposition. 



Pyrophosphate J 2 Soda -^2 nitrate of soda 



of soda \ Phosphoric acid. 



2 Nitrate of f 2 Nitric acid . 



silver \ 2 Oxide of silver ^ Pyrophos. of silv. 



(Bibasic phos. sil.) 



Here there is no salt of water, among the products, and conse- 

 quently the liquid is neutral after precipitation. 



The metaphosphate of soda, which is monobasic, like the 

 sulphates, nitrates and other familiar salts, decomposes, like 

 them, but one proportion of nitrate of silver, and forms a white 

 precipitate; thus 



Before decomposition. After decomposition. 



Metaphosph. f Soda Nitrate of soda 



of soda 1 Phosphoric acid ^S 

 Nitrate of f Nitric acid . . v> < C 



silver \ Oxide of silver ___\^Metaphosphate of silv. 



(Monobasic phos. silv.) 



If acetate or nitrate of lead be substituted for nitrate of silver 

 in these decompositions, a tribasic, bibasic or monobasic salt of 

 lead is obtained in the same manner ; and these salts, again, 



