322 Mr. Maddrell on the Metaphosphates. 



extreme attenuation of which it is susceptible ; and that, what- 

 ever be the quantity of iron contained in a body, it is appre- 

 ciable by the magnetic process as much as it is by chemical 

 means. 



From general considerations, and from very numerous 

 facts stated in this memoir, and from numerous others for 

 which there was no room, it results : — 



1. That iron, although eminently magnetic, is not the only 

 body which possesses this property. 



2. That its tendency to acquire this state is dependent upon 

 its purity, and varies with its coipbination. 



3. Lastly, that the magnetic power acting upon all bodies, 

 either giving them a direction parallel to the current or trans- 

 verse to this current, the fluid, the magnetic agent, possesses, 

 like all other imponderable fluids or agents, universality of 

 influence in nature. 



L. On the Metaphosphates, 

 By Robert Maddrell, Esq.^ 



pTAVING had my attention drawn to a new method for 

 -*- •*- preparing pure phosphoric acid from bone-ash, proposed 

 by Professor Gregory, and a new and apparently anomalous 

 phosphate of magnesia, accidentally discovered by him whilst 

 trying to obtain the above-mentioned acid pure by heating at 

 a temperature above 600° F.f, I was induced at the sugges- 

 tion, and with the kind assistance of Professor von Liebig, 

 to repeat the process, and also to prepare a quantity of the 

 salt, and subject it to analysis. The general results I have 

 found are as follows : — If phosphoric acid, freed from lime 

 and suli^huric acid |, be heated to a temperature above 600° F., 

 it deposits a white substance, having all the general physical 

 characters of the new salt, but in which I found on analysis 

 22'47 per cent, of magnesia, corresponding to the metaphos- 

 phate of magnesia (MgO PO5). After a considerable quantity 

 of this substance had been deposited, I digested the mass in 

 ■water, filtered, and evaporated the solution, and again heated 

 the acid to upwards of 600° F., under the impression that it 

 might still contain the new compound ; by continuing this 

 heat for half an hour, I again obtained a quantity of meta- 



* Communicated by the Chemical Society: having been read Dec. 7, 

 1846. 

 t See Transactions of the Royal Society of Edinburgh. 

 X See Geiger's Handbuch der Pharmaeie. 



