THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[THIRD SERIES.] 



SEPTEMBER 184-5. 



XXV. On the Presence of Phosphoric Acid in Rocks and Mi- 

 7ierals. By William Sullivan, Esq.^^ 



¥ N a recent paper in the Philosophical Transactions, Dr. 

 ^ Fownes showed the presence of phosphoric acid in several 

 igneous rocks, and having made some investigations on the 

 same point, I may perhaps be allowed to state them here. 

 About two years ago, Prof. Liebig mentioned to me the im- 

 portance of examining different rocks in order to ascertain, if 

 possible, the presence of phosphoric acid in them, as he con- 

 sidered very naturally that it must be universally present in 

 all soils and in the rocks from which they are derived, as we 

 invariably find it in the ashes of plants. In the winter of 

 184;3-4'4', I made a number of analyses in order to see how 

 far this idea could be borne out, and also to show that impure 

 limestones were better adapted for agricultural purposes than 

 those usually preferred. To these analyses I have since con- 

 siderably added j but the only publicity I gave the matter up 

 to the present time, was a short notice which was published in 

 a Cork newspaper about a year and a half ago, intended prin- 

 cipally for the information of the agriculturists of that lo- 

 cality. 



The ordinary method employed for the detection of phos- 

 phoric acid I found not to answer where the quantity of that 

 substance is very minute ; and besides, it is likely to give er- 

 roneous results where large quantities of iron, alumina and 

 lime are present : indeed, it is chiefly owing to phosphoric acid 

 being thrown down along with these bases in the analyses of 

 minerals containing this acid only in minute quantities, that 

 its presence in most substances of mineral origin has hitherto 

 escaped detection. 



The mode which I adopted is capable of giving the most 

 * Communicated by the Author. 



PhiL Mag. S. 3. Vol. 27. No. 1 79. Sept. 1 84.5. M 



