THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



[THIRD SERIES.] 



MAY 1849. 



XLVI. On the Isomeric Modifications of Phosphoric Acid. 

 By H. Rose, Professor of Chemistry in the University of 

 Berlin^. 



IT has frequently been remarked, that no substance presents 

 greater difficulties in every respect to the chemist in its 

 examination than phosphoric acid ; whilst the longer and more 

 constantly we are engaged in studying the reactions of this 

 acid, the greater do the difficulties become. Every time the 

 investigation is renewed, the chemist meets with new anomalies, 

 and numerous new obscure phaenomena are exhibited, whilst 

 even those previously known are far from being satisfactorily 

 explained. 



Some time since, in an investigation upon the isomeric mo- 

 difications of the peroxide of tin, I drew attention to the fact, 

 that such modifications are principally met with in those me- 

 tallic oxides which possess acid properties; they are almost 

 entirely absent in those which possess strong basic properties. 

 The latter certainly frequently alter in density to a consider- 

 able extent when exposed to various elevated temperatures, 

 becoming at the same time soluble with difficulty or insoluble 

 in acids ; when, however, they are once dissolved, they always 

 exhibit in solution the same reactions. 



Phosphoric acid exhibits paradoxical isomeric properties 

 still more than any metallic acid. After the important disco- 

 very of Clark, the ingenious investigations of Graham did 

 much towards the elucidation of the difficulties ; but by new 

 investigations new facts have been discovered, part of which 

 cannot be satisfactorily explained by Graham's views. 



Assuming, in accordance with Graham's views, the exist- 

 ence of three modifications of phosphoric acid, viz. metaphos- 



* Translated from PoggendorfTs Amialen der Physikund Ckemie,vo\. Ixxvi. 

 p. 1. 



Phil. Mag. S. 3. Vol. 34-. No. 230. May 1849. Y 



