Mr. Warington on the Action of Animal Charcoal. 269 



ture, including the fibrous varieties, belong to the species 

 first described, and are composed of 1 atom of peroxide of 

 iron and 1 atom of water. 



D. 



A solution of persulphate of iron was precipitated when 

 boiling by a solution of carbonate of soda ; the precipitate was 

 washed with large quantities of hot distilled water and then 

 dried at 212°. It was of an orange-brown colour, and had a 

 specific gravity of 3*77. 



To ascertain the degree of purity of this substance, 20 grs. 

 were dissolved in muriatic acicf, and chloride of barium added ; 

 this gave a precipitate which, when ignited, weighed '3 gr. = 

 •1 sulphuric acid. 20 grs. were also dissolved in muriatic acid, 

 and precipitated by caustic ammonia ; the liquid filtered, eva- 

 porated to dryness, and the residue ignited, weighed '298 gr., 

 consisting of sulphate of soda mixed with the oxides of man- 

 ganese and iron. From these experiments it would appear 

 that the substance cannot contain more than about 1 per cent, 

 of impurity derived from its mode of preparation. When ig- 

 nited in a platina crucible it lost 1405 per cent, by one experi- 

 ment, and 14*15 by a second 3 it was therefore 2Fe20j;+ SHO, 



A portion of this substance contained in a test-tube was 

 placed along with a thermometer in a bath of fusible metal ; 

 it began to give off water at about 260° ; it was kept at a little 

 below 400° till no more water was given off; the remainder 

 then lost by ignition 10 per cent. ; it was therefore converted 

 into Fe^Og + HO at that temperature. When the tempera- 

 ture of the bath was raised to 500°, or a little higher, more 

 water was given off, and by weighing it appeared that nine- 

 tenths of the quantity of water contained in the substance 

 could be driven off at that temperature, but not the whole. 



A portion of the native sesquihydrate (B) behaved much in 

 the same manner, and appeared to be converted into FegOg 

 + HO at a temperature between 380° and 400°. 



The native protohydrate (A B) heated to 512° did not lose 

 more than f^jths per cent., this was probably hygrometric. It 

 begins to give off' its water however at a temperature consi- 

 derably below red heat, which is visible by daylight. 



XL. Observations on the Action of Animal Charcoal. 



By Robert Warington, JSsg,* 



A BOUT twelve months since a friend requested that I 



•**• would undertake the performance of an experiment for 



• Communicated by the Chemical Society j having been read March 17, 

 1845. 



