ON THE OXIDES OF IRON. 



3S3 



Thenard considers as a peculiar oxide. According to him 

 there are three oxides of iron, the zchite, the green, and 

 the red*, I prepared a quantity of this supposed whife 

 oxide with all the requisite precautions, but on attempting 

 to dry it, the colour soon changed. It became first green, 

 then black, and last of all red. 100 grains of iron treated 

 in this way were converted into 158*4 grains of a red pow- 

 der, which lost no weight in a red heat. This red powder 

 contained a good deal of sulphuric acid ; for, when dis- 

 solved in muriatic acid, muriate of barytes threw down a a subsulphate. 

 copious white precipitate. Hence it is obvious, that the 

 supposed white oxide is a subsulphate of iron. In my ex- 

 periment the quantity of sulphuric acid present was about 

 13*4 grains. If sulphate of iron reduced to powder be 

 digested in alcohol, it is converted into a similar white sub- 

 sulphate. 



IV. In some of my experiments on the ores of iron, the Supposed na- 

 result .which I obtained did not correspond with the notion "^^P^^^*^^'^^* 

 which I entertained of the composition of black oxide of 



iron : the oxide examined contained less oxigen. Hence I 

 concluded, that there was an oxide of iron in nature con- 

 taining less oxigen than black oxide. But it is obvious, that 

 what I at that time considered as a new oxide is in reality 

 black oxide, and that my black oxide was in reality a mix- 

 ture of the black and the red. I allude to my analysis of 

 iserine and of iron sand; published some time ago in the 

 6th volume of the Transactions of the Royal Society of 

 Edinburgh + . 



V. I know not whether I onght to notice a remark, with Strictures on 



which Mr. Hassenfratz concludes the paper quoted in the *^*^ ^"^""^'^ 



^ nomenclature 



beginning of this dissertation. "Dr. Thomson," says he, by Hassenfiafz 



*' or his translator, employs in the passage above quoted 

 two new words; I. protoxide to signify the oxide with a 

 minimum of oxigen ; 2. peroxide for the oxide with a max- 

 imum of oxigen." Fourcroy and Hauy, he tells us, had 

 already used the word oxidule to denote the black oxide. 

 He then proceeds to explain the etymology of the two terms 

 which I employ. The Greek numeral t^wIoj prefixed to 



* Journal, vol. kIv, p. 224. 



t See Journal, vol. xxviii, p. 19. 



oxide. 



