184 f-ztur&l Hijtory of Lead. [Book VI 



From the component parts of this mineral, the reafort 

 of the explofion will eafily be underftood.; By the 

 friction, the phofphorated hydrogen gas, which it 

 contains, is inflamed, but being encumbered with the 

 mafs of galena with which it is united, the inflamma- 

 tion is rather gradual than inftantaneous. 



Lead, in fome inftances, has been found combined 

 with various acids ; the vitriolic, the phofphoric, the 

 carbonic, and the arfenical. The ores of lead very 

 commonly contain filver, and fometimes antimony. 



In fmelting lead ores the fulphur is diffipated for 

 want of a proper apparatus for collecting it. Ac- 

 cording; to bifhop Wation's experiments, the Derby- 

 fhire lead ores contain in general from one-feventh to 

 one-eighth part of their weight of fulphur. One of 

 the chief circumftances to. be attended to in the fmelt- 

 ing of lead ores, particularly fuch as contain much 

 fulphur, is to keep them for fome hours in a moderate 

 heat, by which that fubflance may be gradually diffi- 

 pated. After this the fire muft be raifed to fufe the 

 mafs completely, by which the metal flows through 

 the IcoriiE, and is collected in the cavity at the bottom 

 of the furnace. The -.fcoriae being then thickened by 

 the addition of lime, fo that they may be raked afide 5 

 a ftopper is drawn out, and the lead fuffered to flow into 

 an iron pot, whence it is laded into moulds, which form 

 it into the mafies called pigs of lead. 



Lead is foluble in the concentrated vitriolic acid, 



by the affiftance of heat only. The lead then forms, 



the vitriolic acid, a fubftance icarceiy foluble in 



wa:er. It feems to have a peculiar affinity with this 



I, and leaves all others to combine with it, which 



.iot the cafe with the other metals. 



The nitrous acid acls flrongly on .lead. When the 

 is concentrated, it corrodes the lead into a white 



