Additional Observations on Chemical Symbols. 403 



acid, N 9 HP. This is common phosphate of soda; and the one 

 atom of basic water which it contains may yet be supplanted 

 by treating the salt with caustic soda; whence results subphos- 



phate of soda, N 3 P." In fine, there appear to be three classes 

 of phosphates derivable from the three hydrates of phosphoric 

 acid ; and every member of the same class contains the same 

 number of atoms of base. In the following Table this view 

 of the modifications of phosphoric acid is exhibited, and also 

 the salts of soda which the acid forms. The names, when 

 not new, are applied to the salts which they have hitherto de- 

 signated. 



First class, or phosphates containing three atoms ot base. 



Acid. 



| In Atoms. 



Water. Soda. '' Acid. Water. Soda 



Common phosphoric acid 892-3. . .337'5. . . 0- 



Diphosphate of soda 892-3. . .225- . . .390-9 



Phosphate of soda 892-3.. .112-5.. .781-8 



Snhphosphate of soda.... 892-3... Q-...1172-7 



1...3...0 

 1...2...1 

 1... 1 ...2 

 1... 0...3 



Formula. 



H»"P 

 N H a P 

 N 2 HP 



N'P' 



Second class, or phosphates containing two atoms of base. 



Acid. Water. Soda. 



In Atoms, i 



Acid. Water. Soda- Formula. 



Pyrophosphoric acid 892-3.. .225- ... 0- 



Bipyrophosphate of soda 892-3...112-5... 390-9 

 Pyrophosphate of soda- .892-3.. . 0- -781-8 



Third class, or phosphates containing two atom? of base. 



Arid, Water. 



I In Atoms. I 

 Soda.\Acid7water.Soda: Formula. 



Metaphosphoric acid... 892-3... 112-5... 0- 

 Metaphosphate of soda 892-3 0" ... 390-9 



1...1 ...0 

 1...0...1 



HP 



NP' 



I was restrained from proposing any alteration in the no- 

 menclature of these salts, from the difficulty of deciding at 

 present how far the change should be carried. If we confine 

 our attention to the soda in the first class of salts, it is evident 

 that the biphosphate should be called the phosphate, the 

 phosphate be called diphosphate, and the subpbosphate tri- 

 phosphate. But such a change in the names ol common salts 

 would be attended with great inconvenience, and still leave 



f) F 'i 



