g^g OXIDATIONS OF IRON. 



boiling. The fact is very true, but oxigen has nothing to 

 do with it. 

 Effects of oxi- The changes occasioned, according to Mr. Thenard, by 

 gemzed muri- p 0urui g oxigenized muriatic acid into a sulphate of iron pre- 

 cipitating white, agree very well with the idea I have formed 

 of this precipitate. As oxigenized muriatic acid is so little 

 soluble in water, and the sulphate of iron in question so 

 concentrated, it follows, that, if the acid be not very abun- 

 dant in the solution, the precipitate will be green ; because 

 the little oxigen contained in the muriatic acid is capable of 

 converting to red oxide but a small portion of the green, 

 which is so predominant as to envelope the red, and prevent 

 its appearance. It will be the same to the eye as if the so- 

 lution were diluted with water, equal in quantity to the mu- 

 riatic acid, by which the white precipitate would have been 

 changed to green in a similar manner. If, on the contrary, 

 the oxigenized muriatic acid be very abundant, there is no 

 doubt, that the solutions will become red, as is the case with 

 all the green salts of iron. 

 On precipitat- ' With respect to the third fact, namely, that on making 

 ing in a closed t ^ precipitate in a phial, and stopping it immediately, ab- 



phial,air is n t r l . x . r . . , 



absorbed but sorption takes place, and the residual air extinguishes a can- 

 evolved, d]^ i gj^u on |y sa y ? th a t instead of absorption, I have al- 

 ways found an evolution of air, which has sometimes forced 

 out the cork. It is true, that, after the white precipitate 

 |ias passed to green or red, the residual air sometimes extin- 

 guishes a candle ; but this is owing to the extrication of a 

 principle, of which I shall speak presently. 



Of the green oxide. 



Green oxide The green oxide obtained by dissolving iron in acids, of- 



bffers three f ere< j me t ^ ree leading facts to examine. First, to determine 

 questions to be , • , . . , , , . ,1 , , v 



ilved. how much oxigen iron takes to pass to the state ot green 



oxide: secondly, to account for its colour: thirdly, to ob- 

 serve the influence of atmospheric air on these solutions. 

 P'ooorUon of To determine the proportion of oxigen, and observe at the 

 fcxigen. same time the influence of the atmospheric air, 1 took 00 



grains of iron filings, which I divided into three equal parts. 

 Each of these was dissolved separately in muriatic acid diluted 



with 



