THE 



LONDON and EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



JUNE 183*. 



LX1V. Reply to Mr. Phillips's Additional Observations on 

 Chemical Symbols. By Thomas Graham, Esq., M.A., 

 F.R.S.E., Lecture)- on Chemistry in the Andersonian Institu- 

 tion, Glasgow. 



To Richard Phillips, Esq., Z.R.S., %c. 



Dear Sir, . , . , 



I SHALL endeavour to supply the information which you 

 consider still required to render my paper on the phos- 

 phates intelligible, in a brief summary of its principal theore- 

 tical results. For the evidence upon which the conclusions 

 rest, I must refer entirely to the paper itself, which is now be- 

 fore the public. . ' . . . . 

 Two phosphoric acids had been previously recognised, which 

 possess very different properties, judging from the characters 

 of the salts which they form with the same bases. I hese two 

 acids were said to be isomeric bodies, or to be of the same 

 composition and atomic weight, and were distinguished as 

 the phosphoric or common phosphoric add, and the pyrophos- 

 vhoric acid. The observation was made by me that there is 

 a third phosphoric acid, which may be produced by heating 

 the Diphosphate of soda to redness, and by other processes; 

 and to which I applied provisionally the name metaphosphoric 

 acid But on pursuing the investigation, a key to the whole 

 mystery of these compounds was discovered, by means ot 

 which the perplexing mutations to which the acids and then- 

 salts are subject might, it appeared to me, be explained in a 

 satisfactory manner. 



Third Series. Vol. 4. No. 24. June 1 834. S * 



