14 His-toRr of the sociE-rr. 



that there appears no reafon to fuppofe that foft iron can be 

 converted into fteel by carbon penetrating from the fuel through 

 the crucibles. 



Sir George Mackenzie concludes his account of thefe ve- 

 ry interefting experiments with the defcription of one which 

 appears to be entirely new, and tends ftill farther to prove the 

 identity of carbon and diamond. 



Having prepared fome pure oxide of iron from a folution 

 of the fulphate, by precipitation with catiftic ammonia, he mixed 

 a fmall quantity of it with one-fourth of its weight of diamond 

 powder, prepared in the following manner. 



The diamond, being reduced to powder in a fteel mortar, 

 •was boiled in muriatic acid, to diflblve the iron which might 

 have been abraded from it. After proper edulcoratlon, it was 

 heated in a muffle^ to burn off the carbon of the fteel, which 

 remained after treatment with the acid, and which rendered the 

 powder of a grey colour. He obferved the coaly matter take 

 fire at the edge of the heap of powder next the ftrongeft heat, 

 and gradually fpread itfelf, till at laft the whole appeared as if 

 burning. The glow through the powder ceafed foon after, and 

 on removing it, he found it perfedlly clean and white. From 

 the diminution of the original weight of the diamond, he found 

 that a part of it had alfo been confumed. 



The mixture of oxide and diamond powder thus prepared 

 was put into a Cornifli-clay crucible, and expofed to a pretty 

 ftrong heat for half an hour, after which the oxide was found 

 to be reduced into a metallic button of caft-iron *. 



Another portion of the oxide of iron, ufed in this experi- 

 ment, was not reduced, when placed in the fame circumftances, 

 without the diamond. 



MINERALOGY. 



* In the courfe of this experiment it was afcertained, that the fufing point of 

 iron is between 153° and 158° of Wedgwood's pyrometer. 



