224 On the Composition of an Acid Oxide of Iron. 



the three analyses of this barytic salt should respectively in- 

 dicate, if the loss sustained in these be only water, 2*18 grs. 

 3*38 grs., and 2*44 grs., a result, as will be seen by reference, 

 so near the loss sustained in analysis, that the difference may 

 fairly be reckoned as merely an error of experiment. The 

 results obtained from the three foregoing analyses, reckoning 

 the loss as water and deducting the silica and sulphate of bary- 

 tes as impurities, will give respectively 30'38 grs., 4-6*99 grs., 

 and 33*78 grs., as the quantities of pure ferrate of barytes 

 operated upon, yielding- 



30-38 46-99 33'78 



The mean of which will give 1956 of barytes, 1T64 of ses- 

 quioxide of iron, 3*35 of oxygen, and 2*31 of water contained 

 in 37*06 of ferrate barytes. 



The 11*64 parts of sesquioxide of iron are composed of 

 8-15 of iron and 3*49 of oxygen, which uniting with the 3*55 

 of oxygen gas (within -06 of a grain in 37*06 grs. of the quan- 

 tity theoretically required), will yield 15*19 of teroxide of iron, 

 or ferric acid, combined with 19-56 parts of barytes, indi- 

 cating the formula BaO F0 3 HO as the composition of this 

 salt. 



37*06 37*06 



I therefore consider the acid oxide of iron present in the 

 deep amethystine solution of the potash salt, and in combina- 

 tion with barytes in the crimson-red barytic salt, to be a ter- 

 oxide of iron, containing twice the quantity of oxygen exist- 

 ing in the sesquioxide. Whether the pink salt obtained by 

 the agency of chlorine is another and distinct combination of 

 iron with oxygen, forming a still more highly oxygenated com- 

 pound than ferric acid, I am at present unable to state, but I 

 am inclined to this opinion ; it is certain, however, that another 

 acid oxide of iron exists, probably of a lower degree of oxida- 

 tion than the ferric acid. The combination of this acid with 

 potash or soda is of a beautiful emerald-green colour, pre- 

 cisely similar to the green manganate of potash. The condi- 

 tions requisite to procure this compound I am at present un- 

 able to point out, but I have generally succeeded when I have 



