Chap. 31.] [ 181 ] 



CHAP. XXXI. 



LEAD. 



General Properties of Lead. Red Lead. Litharge. Natural Hiftsry 

 of Lead. Slickenjides. Curious Phenomenon. Smelting Lead Ores. 

 *Union iu;th Acids,- Plumbum Corncnm. White Lead', bony 

 made. Sugar of Lead. Union -"with other Metals.~ Common Saltier, 

 U/es of Lead.- Great Danger from leaden F'ejJ~els.De : UGnJhire 

 Colic. Means of deleting Lead in Liquors. Medical Ufes of Lead. 

 Ufes of its Calces in the Arts. 



THE appearance of this metal is well known. It 

 is fo Toft as to be cut with a knife without much 

 difficulty. It is neither fonorous nor elafdc. It has 

 very little tenacity, and therefore cannot be drawn 

 into fine wire. It fpreads eafily under the hammer, 

 but cannot be extended into very thin leaves like gold, 

 filver, and tin. Its fpecific gravity is rather greater 

 than that of filver, being eleven times heavier than 

 water, and it is exceeded in this refpect by only three 

 metals, gold, platina, and mercury. Lead melts at 

 the five hundred and fortieth degree of Fahrenheit's 

 thermometer, before it becomes red hot. 



Lead, like tin, at a certain point between its fluid 

 and folid ftates, poffefles very little cohefion, and may 

 be fcparated by a fmart blow with a hammer into 

 grains, which are ufed in ai&ying the ores of gold and 

 filver. 



Lead, foon after it is melted 3 acquires a film on its 

 furface, which prefents in fuccefiion a variety of co- 

 lours. This film becomes thicker, and of a grey co- 

 lour, by the continuance of the calcination, and is then 

 called plumbum uftum. If the firil pellicle is re- 

 moved, another is o A uickly formed, and in this way 

 N 3 almoft 



