On the AJJajmg of Ores hjy Fujton. 389- 



varieties fufceptible of various degrees of carbonation : for 

 the moft part I have ufed chalk and charcoal for the reduc- 

 tion of the ore into carbonated crude iron. In the hsema- 

 tites variety, for i lb. averdupoife I have commonly added 

 6 oz. dried chalk and 3-4ths oz. of charcoal; and for the 

 fplinty blue ore alfo a limilar mixture. From both of thefe 

 I have obtained the richeft fort of crude iron. In the manu- 

 factory thefe varieties are always reckoned to produce the 

 hardeft and moft infufible qualities of crude iron : when the 



carbon or. oxygen will not nearly explain this phenomenon, as theyexift in 

 much lefs proportion; and while the jron remains in a crude ftate, the lat- 

 ter accumulates in proportion as the former becomes espelled. Befides, a 

 greater produft in malleable iron is obtained by following the precautions 

 formerly mentioned, than even of caft-iron when thus expofed. Now, as 

 malleable iron is free from all mixture, or at Icaft is malleabk in propor- 

 tion as it is unalloyed, it is obvious that the deficient weight is not made 

 yp of either oxygen or carbon. In the expofure of one particular button 

 of crude iron, whicji loft gi [>er cent, the furface was agitated in an 

 uncommon and moft beautiful manner; a rapid motion from the ex- 

 tremity of the circumference to the centre of the fluid mafs took place j 

 the motion feemed entirely rotatory, and peculiar to one common 

 axis. The mcta! itfelf was of a blueifh green colour, and emitted from 

 its furface an azure-coloured gas, which preferred a diftinft form and co- 

 lour from the common flame.. This appearance firft led me to fuppofe the 

 preferice of the ferric acid, by which means the lofs of weight, v/hen no 

 oxyde was vifible, would be eafily accounted for. To try, fo far, the 

 juftice of this conj'fture, I expofed tin, lead, and zinc, in difFercnt alloys 

 of thefe metals, to white heats, and found them diifipate in a much ftiorter 

 time, and with a greater difcharge of gas from their refpeftive furfaccs. 

 The fame efiFcft was more fpeedily produced by introducing the pieces 

 upon the furface of hot melted crude-iron. Zinc, in this experiment, in- 

 flames" inftantaneoufly ; explodes with confiderable violence, and with the 

 difengagemcnt of a blueifh flame. Its known inflammable property may 

 add little ftrciigth to this hypothecs; but the dillipation of lead and tin, 

 without any rcfukic, would alfo lead to a fuppofuion of the plombic and 

 llinnic acids being formed by a complete faturation of oxygen. The latter, 

 being found formed by nature in a cryftaUine form, does not entirely con- 

 tradift this idea ; for a difference in the dofc of oxygen, ar.d of tempera- 

 ture, mult iiltcr the refult. 



C c 1. riiet.u 



