Existence of Compound Radicals in Amphide Salts. 65 



to differ from each other only in the proportions of water, or oth- 

 er base which they require severally for their saturation ; so that 

 there is a monobasic, a bibasic, and tribasic phosphoric acid. 

 When in the state heretofore designated as free, they are consid- 

 ered as constituting three phosphates of water. This assumed 

 constitution of these isomeric acids has been represented by Dr. 

 Kane, and other respectable chemists, as affording strong evidence 

 of the existence of compound radicals in certain salts. Dr. Hare 

 has in arguing against the existence of such radicals, adverted to 

 the constitution of the different phosphates of water.* Hence it 

 is deemed expedient to give, in the language of Dr. Kanef an 

 account of the acids of phosphorus to which reference is made, 

 and of their habitudes with basic water and other bases. 



" The phosphoric acid has a great affinity for water, combining 

 with it almost explosively. It may form three distinct com- 

 pounds, phosphates of water, the constitution of which is as fol- 

 lows : — 



Monobasic phosphate of water, - - P0 5 +HO. 

 Bibasic phosphate of water, - - P0 5 +2HO. 



Tribasic phosphate of water, - - P0 5 -f-3HO. 



" This relation was first established by the researches cf Gra- 

 ham. Phosphoric acid combines not only with water in these 

 three proportions, but each of them is a type of a series of salts, 

 which the phosphoric acid is capable of forming. Thus there is 

 a class of monobasic phosphates, another class of bibasic phos- 

 phates, and a third, which is the most common, of tribasic phos- 

 phates ; the water contained in the phosphates of water being re- 

 placed to a greater or less extent, by means of equivalent propor- 

 tions of ammonia or metallic oxides. 



"A solution of phosphoric acid in water, may contain any one 

 of the three phosphates of water that have been described, and 

 when neutralized by bases may hence produce totally different 

 salts. The properties of a solution of phosphoric acid may, there- 

 fore, be totally different according to the manner in which it had 

 been prepared, and hence this acid was at one time ranked as a 

 remarkable instance of isomerism ; but Graham has beautifully 

 shown, that the difference of properties is only the result of the 



* See Effort to refute the arguments in favor of the existence in amphide salts of 

 a compound radical like cyanogen. 

 t Elements, page 485. 

 Vol. xlvi, No. 1.— Oct.-Dec. 1843. 9 



