ON CAST IRON. 39 



ceffion ; bat inflead of the frothy fcoria obtained in the firft The fcoria 

 eflay, a very fluid ftratum was formed, which diffiifed itfelf m 

 over the melted metal, and prevented its refining. This fco- It was blackirti 

 ria, when grown folid, was of a blackifli brown colour and £™ ""j^a* *£ 

 vitreous fracture. We endeavoured more than once to re- and not to be 

 ■move it, but the flratum was fo thin as to render it impracVi- reraoved * 

 cable : As foon as one ftratum was removed, another formed. Stirring pro- 

 At the expiration of four hours, the metal being ftill very fluid, J^*^™ 

 we began to ftir it, in order to bring its different parts fuceef- filiating com- 

 fively into contact with the air ; this produced an extraordinary buftion. 

 heat in the furnace, combuftion, and fcintillation, refembling 

 that which takes place when iron wire is burnt in oxigen gas. 

 This oxidation always produced freth fcoria : as foon as we 

 defifted from ftirring, every thing became quiet, and the ftra- 

 tum of fcoria prevented the oxidation. At length, after three 

 hours longer, making feven in all, during which the melted 

 niafs had frequently been ftirred, it feemed to thicken ; per- 

 ceiving too, that it diminished confiderably in quant'* y, the 

 fire was damped, and the matter left to cool in the furnace. It T !? e lton , had 



• i i r it • *°" : muc « m 



was afterward weighed, and found to have loft much of its we ight. 

 weight. Its extraordinary fracture gave reafon to prefume a Its fracture com- 

 high degree of oxidation ; for inflead of being gray and gra- p3 "'very, 



nulous, it was compact, and of a filver white. It was inter- Porous, 

 fperfed with a large quantity of fpherical cavities, greater or 

 lefs in fize, which evidently announced the exiftence of an ae- 

 riform fluid, that had been extricated during the fu (ion. 



This mafs was too fmall to be refined. Having examined There was much 

 the quantity of oxigen it contained in the fame manner as withyj^j^g,. ac _ 

 the other fpecimens, I found that four ounces yielded 87 cubic quired much ox- 

 inches of oxigen gas, and coniequently nine inches lefs than isen> 

 that which had been treated by means of aqueous vapour. 

 Thus probably here too the oxidation was too powerful, and 

 the iron was fuper-refined. As the metal did not become without pafling 



doughy in the courfe of the proeefs, it muft have been fuper- thvou §" t Jj e 



h J ,. malleable ftate. 



faturated with oxigen without pafling through the ftate of mal- 

 leable iron. The carburet, it is true, muft have been totally The carburet 

 deftroyed during the operation, which produced the fiivery deftr °y ed * 

 hue. 



Remarks 



