<g$0 OXIDATIONS OF IRON. 



Scarcely was the mass dry, when the retort burst, and I 

 found in it more than 300 grains of red oxide, with a little 

 green oxide, which occupied the bottom of the retort. The 

 pressure of the red oxide and sulphate of soda, by which 

 the green oxide was covered, had prevented the disengage- 

 ment of the hidrogen from this portion. 

 Proof that In support of my opinion 1 shall add two facts, which, 



fron does' not° though less direct than those I have already given, %re of 

 acquire move considerable weight. When oxigenized muriatic acid is 



oxigen from pourec l on a green solution, if the oxigen of the acid com- 

 oxigenized " ° ° , , . 



muriatic acid, bined with the oxide of iron, a considerable extrication of 



caloric must take place, in consequence of its more dilated 

 state in the acid, and more condensed or fixed state in the 

 oxide, from which the greatest heat of our furnaces cannot 

 expel an atom. But I convinced myself by several experi- 

 ments, that the increase of temperature is scarcely percepti- 

 ble. This slight evolution of caloric is consistent with the 

 combination of the hidrogen, given out by the hidruret of 

 iron, and the oxigen from the muriatic acid, because in both 

 these combinations the gasses are nearly in the same state of 

 dilatation as when they form water. 

 ?roof that sul • Lastly, if the action of sulphuretted hidrogen on a red 

 droSfdoes'" solution of iron be merely to bring it back to the same de- 

 oot deprive it gree of oxidation, as that in which the common green solu- 

 of oxigen. tiong are ^ the p r0 p er ties of both should be the same. On 

 the contrary, the solutions rendered green by sulphuretted 

 hidrogen rapidly change red on exposure to the air ; and 

 heated for a quarter of an hour they become entirely red : 

 which is not the case with the common green salts recently 

 made. 



(To be concluded in our nexi.J 



VI. 



