Cast Iron, Steely and Malleable Iron. 5 1 5 



After boiling for more than twenty-four hours, 20*4 grains 

 left a dark-green residuum, weighing only 2*64 grains, and 

 this residuum burnt in a dried stream of air in a horizontal 

 glass tube, blackened with the first action of heat, and drops 

 of water collected on the upper part of the tube. After the 

 water was driven into its receiver, brown spots remained on 

 the glass ; the drops of water collected smelt as if impregnated 

 with tobacco-smoke, and the gas which escaped from the ap- 

 paratus for collectinjr carbonic acid had the same smell. 



I collected carbonic acid O'Oo^ : water 0'238: and there 

 remained white silicon = '1'2)5. 



For 0-954 carbonic acid is = 0-2637810 carbon; and 0-238 

 water is = 0'026394'2 hydrogen. Sum of carbon and hydrogen 

 0-2901752. This last amount is only less 0-1998848 grain and 

 to account for the loss of cai'bon, hydrogen and azote which 

 passed through the bulb glass containing the caustic ley in 

 the form of the before-mentioned nicotianic gas. 



By boiling the residuum of white iron for a short time only 

 in hydrochloric acid, very little iron is dissolved, and the 

 remainder assumes a greyish colour, and becomes white or 

 grey after the first ignition without first glowing like tinder. 



By boiling it with caustic alkalis only traces of silica are 

 extracted, whilst a species of brownish humus was dissolved, 

 which I found never to exceed in amount 2 per cent. ; the silica 

 therefore must be contained in a chemical combination with 

 carbon, azote and iron. 



A short ignition of the residuum on the contrary is suffi- 

 cient to make the greatest part of the iron soluble in acids. 

 If it is only heated, till it begins of itself to glow, the iron is 

 dissolved by acids, and the evolution of hydrogen shews that 

 the iron must be contained in a metallic state in the residuum. 

 When, on the contrary, this remainder is heated as long as it 

 absorbs oxygen, and then treated with acids, no evolution of 

 gas takes place, and a mixture of protoxide and peroxide of 

 iron is dissolved. 



As soon as this residuum begins to glow, carbonic acid, 

 azote and a little hydrogen are invariably evolved, which 

 shows the intimate connexion between the solubility of the 

 iron and the carbon, azote and hydrogen in the residuums. 



Not only the evolution of hydrogen gas, but the powerful 

 action on the magnet, proves, that the iron in these residuums 

 must be contained in the metallic state. Even A^ere we to con- 

 sider it as protoxide, the great increase of weight, that is, the 

 absorption of oxygen, which takes place during ignition, could 

 not be accounted for. But as the iron, notwithstanding its 

 metallic state, is not soluble in acids before ignition, we must 



2 M 2 



