"" CHEMISTRY. 



pWt reacting upon one another, produce sulphurous acid, and free 



Frojy.—Asoru bluish metal ; has a metallic lustre when freshly 

 cut; somewhat malleable and ductile, particularly in the fJZof 

 pipes; not very tenacious; sp.gr. 11.45; melts at 600° F. Exposed 

 to moist air, it becomes coated with a film of the dioxide; also ab- 



Fn in7F"T7r " ^T'^ ^" '^' "P^^ ^''' Sy^b. (Plumbum) Pb. 

 i^q. 106'b. It forms four oxides. ^ 



Dioxide, Pb,0, formed by heating dry oxalate of lead in a retort ; 

 It absorbs oxygen very rapidly. 



Protoxide, PbO the basis of* the salts of lead, is prepared by ex- 

 posing the gray film which collects on the surface of melted lead, 

 and which consists of the protoxide and metallic lead, to a hi^h heat 

 wjth the access of air; this constitutes the massicot of commerce ,' 

 when partially fused by heat, it becomes litharge; in this state it 

 contams some peroxide. It has a yellow colour, is insoluble in 

 water unites with acids, forming salts, from which it is precipitated 

 by alkalies as a hydrate, and as ivhite lead by alkaline carbonates 



Peroxide,puceox broton oxide, PbO„ prepared by the action of 

 nitric acid or red lead, which converts it into the protoxide and per- 

 oxide. It has a flea-colour ; is insoluble ; by heat, it is converted into 

 protoxide and oxygen. 



Red lead, minium, or red lead, "P^O^, or 2PbO + PbO con- 

 sidered to be a compound of the protoxide and peroxide ; is formed 

 by exposing lead to heat in the air, without allowina it to fuse It 

 is a heavy, brilliant red powder; decomposed, with the evolution 

 ot oxygen, by a strong heat; and converted into a mixture of prot- 

 oxide and peroxide by acids. It is used as a pigment, and in the 

 manufacture of flint-glass. 



Chlorine forms with lead a compound known as plumbum cor- 

 nezmz, or hovn lead. Sulphur forms with lead the well-known 

 ga/ena which occurs in cubical crystals. Iodine, bromine, fluorine, 

 and phosphorus also form compounds with lead. The most im- 

 portant salts of lead are the carbonate and acetate ; also the nitrate 

 and sulphate. 



Carbonate of lead. White lead,— is sometimes found in a native 

 crystalline state ; may be prepared by precipitating? from any soluble 

 salt of lead by means of an alkaline carbonaie ;— is manufactured by 

 exposing sheet-lead in coils to the action of the vapour of vinegar, at 

 the temperature of decomposing manure: the lead is oxidized, and 

 then converted into a carbonate by the carbonic acid, which is de- 

 rived from the decomposition of the acetic acid. It is a soft, white 

 very heavy powder, insoluble in water; much used as a pigment. 



Acetate of lead. Sugar of lead,— made by dissolving litharge* in 

 acetic acid ; occurs in colourless, transparent crystals ; has a sweet 

 taste ; is very soluble in water, also in alcohol. There are several 



