588 LEAD. 



solution has been employed to dye the hair black. The oxide of 

 lead combines readily with the earths and metallic oxides l}y 

 fusion, and when added to the materials of glass imparts bril- 

 liancy to it and increased fusibility. 



Oxide of lead is a powerful base, resembling barytes and 

 strontian, and affords a class of salts which often agree in form 

 and in general properties with the salts of these earths. Its 

 carbonate occurs in plumbocalcite, in the form of carbonate of 

 lime ; an isomorphism by which the protoxide of lead is con- 

 nected with the magnesian oxides. All its soluble salts are 

 poisonous, although no salt of lead, with the exception of the 

 carbonate, which is insoluble, is highly so (Dr. A. T. Thomson). 

 Lead is precipitated by sulphuretted hydrogen, as a black sul- 

 phuret, even from acid solutions. Neutral salts of lead are also 

 precipitated by solutions of carbonates, chlorides, sulphates, 

 phosphates, etc., the corresponding salts of lead being insoluble. 

 Iodide of potassium and red chromate of potash produce yellow 

 precipitates in salts of lead, which are highly characteristic of 

 the metal. Iron and zinc throw down metallic lead. If a mass 

 of zinc be suspended in a solution, made by dissolving one 

 ounce of acetate of lead in two pounds of distilled water, the 

 lead is precipitated in beautiful crystalline plates, which are 

 deposited only in metallic contact with the zinc, but extend from 

 it to a considerable distance in the liquid, forming what is called 

 the lead tree. 



Peroxide of lead, PbO 2 , may be obtained in the same man- 

 ner as the peroxides of cobalt and nickel, exposing the pro- 

 toxide suspended in water to a stream of chlorine ; also by 

 fusing protoxide of lead with chlorate of potash at a tempera- 

 ture short of redness ; or by digesting the following intermediate 

 oxide, minium, in diluted nitric acid, which dissolves protoxide 

 of lead, decanting off the nitrate of lead, and washing the 

 powder which remains with boiling water. Peroxide of lead is 

 of a dark earthy brown colour. It loses half its oxygen by ig- 

 nition, absorbs sulphurous acid with great avidity and becomes 

 sulphate of lead, affords chlorine when digested in hydrochloric 

 acid, and the nitrate of protoxide of lead with water, when 

 digested in ammonia. 



Minium or Red lead is formed by heating massicot or pro- 

 toxide of lead, which has not been fused, to incipient redness in 

 a flat furnace, of a particular construction, and directing a cur- 



