370 SALTS 



1 atom carbonic acid 



1 atom protoxide of lead 1 4 



16-75 



Phosphate, 7. Phosphate of lead. This salt exists native, 

 and is often crystallized in six-sided prisms. It 

 is anhydrous ; but never quite pure, containing 

 a little muriatic acid and some oxide of iron. 

 It is very difficult to form a neutral phosphate 

 of lead artificially, for the acid and oxide are 

 capable of combining in two proportions ; name- 

 ly, 1 atom acid and 1 atom oxide, and 1 atom 

 acid and 2 atoms oxide ; and in general variable 

 proportions of the diphosphate mix themselves 

 with the neutral phosphate, and render the re- 

 sult uncertain and inconstant. The constituents 

 of the neutral phosphate are 



1 atom phosphoric acid 3-5 



1 atom protoxide of lead 14 



17-5 

 The constituents of the diphosphate are 



1 atom phosphoric acid 3-5 



2 atoms protoxide of lead 28 



31-5 



8. Arscniatc of lead. This salt has been 

 found native in different places. Fine crystals 

 of it in large six-sided prisms of a yellowish co- 



