ON THE OXIDES OP IRON. 355 



Examination of the Red Oxide of Iron at a high Tem- 

 perature, 



A hnndred grains of red oxide were put into a Hessian Red oxide ex- 

 crucible previously weighed, and this was placed in a larger. |j|°^j to a white 

 The whole was kept at a white heat in a forge fire for three 

 quarters of an hour. The bottom of the lower crucible 

 was vitrified. The oxide was become a blackish steel gray 

 powder, with a metallic lustre, attractable by the magnet. 

 It had lost three grains. 



The same quantity of red oxide was kept at a white heat 

 for an hour and half. Its loss then was six grains and half. 

 The lower stratum of oxide was completely fused, of a 

 clean fracture, a steel gray, and a metallic lustre. The converted part- 

 upper stratum M^as imperfectly fused, crystallized at the ^.*?^° 

 surface, and porous internally. It was a mixture of the 

 red and black oxides of iron. 



Though a white heat causes the red oxide to pass to the A red heat has 

 state of black, there is no fear of a red heat producing ""' '^'* ^^"'^*' 

 this effect. 



Manner in which Iron and its Oxides comport themselves 

 ■vcith Nitric Acid, 



Nitric acid greatly diluted with water dissolves iren^ and Action of nitric 

 produces the nitrate in which iron is oxided at a minimum. '^^^ °" "^°"' 

 Proust and Davy had already shown the same. This state 

 however possesses little permanence, for if the liquid be 

 heated ever so little, or the acid be not very weak, a nitrate 

 at a maximum is obtained. 



The latter being boiled down quickly, set to cool, and 

 cold water poured on it, a red substance insoluble in water, 

 but soluble in nitric acid, was separated. This red sub- 

 stance gave out red fumes when calcined, and a red oxide of 

 iron remained. 



The nitrate of iron is not decomposed, when it is boiled 

 down very gently. It leaves a thick residuum of a brown 

 red colour, which attracts moisture from the air, and is 

 perfectly soluble in water. 



The red oxide of iron is soluble in nitric acid in a certain and on the red 

 degree hy means of heat. This action of the nitric acid °^^ '^• 

 2 A 2 however 



