Chap. 3i ] While Lead. 185 



calx; but if it is confiderably diluted, it diffolves the 

 lead. This folution does not afford a precipitate on 

 the addition of water. Its cryftals, obtained by cool- 

 ing, are of an opake white. Th;s fait decrepitates in 

 the fire, and melts with a yellowifh flame when laid on 

 ignited charcoal. The calx, which is nt firft yellow, 

 is quickly reduced into globules of lead. The vitrio- 

 lic acid added to this folution combines with the me- 

 tal, and forms a precipitation. The marine acid, in 

 the fame manner, feizes the lead, and forms a combi- 

 nation, which., if expofed to heat, melts into a mafs of 

 a brown colour, called plumbum corneum, from fome 

 refemblance to the combination of the fame acid with 

 filver, called argentum corneum. 



The acetous acid, or vinegar, acts on lead, particu- 

 larly when applied to it in fleam, in which proccfs the 

 action of the air probably affifts that of the acid. To 

 procure white lead, fheets, of lead are rolled up lr>i- 

 rally, fo as to leave the fpace of about an inch 

 each coil, and placed vertically in earthen po.-s, v>!,ich 

 have fome good vinegar at the bottom. Ti.c nots 

 are covered, and expofed to a gentle heat for a v ,fi- 

 derable time by furrounding them with horie dung. 

 The fleams of the vinegar circulate in the vrOrj, and 

 attach themfelves to the furface of the Icr ; : c^n vert- 

 ing it into white flakes, v.hich come off when '.lie lead' 

 is uncoiled. The remaining lead is ag T. -xr>ofed to 

 the fleams of the vinegar, till another 6ru& L formed, 

 and the proceli is repeated till its L M ce is 



converted into the white flaky matter dllc-i c^rule, or 

 white lead. 



Such are the deleterious effects of ..> . ', . !u n taken 

 into the huuian body, that? the wr. 

 white lead works are ieldoin knov. 

 three years, when they exp. 



pajn 



