OXIDATIONS OF IRON. g^fj 



alkali* is added to it, and the glass shaken a little: and we ides of iron 

 cannot allege, that this smell is owing to a few globules ©f proved by the 

 hidrogen, that have remained mechanically entangled in the 

 solution, binee the same phenomenon takes place, if the so- 

 lution be previously boiled. If the solution be diluted with 

 six or eight parts of water at 50° or 60° [144° or 167 F.], 

 and it be stirred with a glass rod as the alkali is put in, the 

 smell is still very strong, and continues to exhale as long as 

 an atom of green oxide remains in the precipitate^ so that it 

 is easy to tell by this, without seeing the precipitate, whe- 

 ther the solution be red or green. . When a little green sul- and by the gas 

 phate of iron in a very concentrated solution, like that which evoIv;;d - 

 gives a white precipitate, is precipitated in a phial, and this 

 is corked and shaken, it will be seen, that the volume of 

 gas is increased ; for, if the cork do not fit very tight, it will 

 be forced out, notwithstanding the temperature continues 

 the same. If the air in the phial be afterward examined, it. 

 will be found sometimes to extinguish a candle, or to deto- 

 nate on its application. Now both these are compatible with 

 the presence of hidrogen, according as it is pure or mixed ; 

 and possibly there may be a little iron dissolved in it, as zinc 

 or arsenic sometimes is. 



To satisfy myself still farther cf the presence of hidro- 

 gen, and its influence on the salts of iron, I adapted to a 

 tubulated retort a small receiver, and to this a curved tube, 



the extremity of which opened under a jar in the pneumatic 



-r 1 -r 1 , • ' ' * , Farther proof 



apparatus. Into the retort 1 poured a solution of green sul- i, y expelling 



phate of iron recently made, having- previously boiled it half the hidrogen. 



an hour, to prevent any suspicion cf hidrogen mechanically 



retained in it. This solution I precipitated with caustic 



Boda greatly diluted with boiling water. As soon as the 



mixture was brought to boil, a gas fetid as hidrogen was 



evolved, which detonated on the contact of flame. The 



water of the pneumatic apparatus too had the nauseous 



taste and smell of hidrogen disengaged from solutions of 



iron. 



In order to expel all the hidrogen, or to convert all the 



•side from green to red, I continued the distillation. 



* If am-monia be used, its smell conceals that of the hidrogen. 



Scarcely 



