OXIDATIONS OF IRON. 277* 



delated, that oxigen has no influence in the red or green co- 

 lour of oxides of iron. I meditated some experiments there- 

 fore, tending to observe the mode of action of these two 

 reagents, when I recollected a fact observed at the beginning 

 of my inquiry, which thus indemnified me for a number of 

 errours, into which ic had led me before. 



In every kind of iron I had hitherto treated I found a sub- White precipi- 

 stance, that fell down in a white precipitate, did not change tate rom iron ' 

 by exposure to the air, gave an emerald green precipitate 

 with prussiate of potash, and which I believe to be what Supposed tobe 

 I-* • • r» • -* pliosphuret ot 



Bergman called sidente, rather than phosphate of iron. On iron. 



the other hand I obtained from some red salts of iron a white 



precipitate, that sometimes crystallized in laminae very soft to Sometimes re ~ 

 11 . ^ , . sembling stea- 



the touch, which the most experienced minei-alogist would tites. 



take for French chalk, but Avhich is nothing but a salt of 



iron with excess of oxide. I thought at the time, that these Both imagined 

 t i ,1 ,t -i to be magnesia. 



two substances were the same, that they were magnesia, and 



that this was nothing but iron at a maximum of oxidation. 

 The name of this earth favoured the illusion; as did the opi- 

 nion of former chemists respecting the transmutation of me- 

 tals into earths. I deferred the investigation of this subject 

 to a future period, making in the mean time only a few ex- 

 periments on magnesia ; and I found, that, on treating solu- 

 tions of this earth with sulphuretted hidrogen, it afforded Sulphuretted 



. ., , . , „ . hidrogen prect- 



a precipitate similar to the green oxide or iron. pitates.magne. 



Though my farther reserches concerning iron taught me, sia & reen > 

 that neither of these substances was magnesia, the way in 

 which this earth was coloured by sulphuretted hidrogen was 

 a fact, the reason of which I intended to make the subject 

 ©f future inquiry ; and which, on recurring afresh to my me- 

 mory, led me to suspect, that sulphuretted hidrogen might 

 have a mode of action different from any with which we were 

 acquainted. I was eager to repeat this experiment, not only 



on magnesia, but on lime and alumine likewise, and I found as \ l does lime 



° h and aluimne. 



in fact, that the soluble salts of these three earths, treated 



by sulphuretted hidrogen, gave precipitates altogether simi- 



.lar to the green oxide of iron*. These precipitates exposed 



to 



* Certain management is necessary, to succeed in this experiment, 

 j which I have not repeated often enough, to be able to give certain in- 

 struction 



