590 LEAD. 



a persulphuret of lead, but is almost immediately changed into 

 the black protosulphuret of lead and free sulphur. 



Chloride of lead, Pb Cl, 1737.15 or 139.2. Lead dissolves 

 slowly in hydrochloric acid, by substitution for hydrogen, form- 

 ing the chloride of lead. The same compound is obtained by 

 digesting oxide of lead in hydrochloric acid, and also falls as 

 a white precipitate, when a salt of lead is added to any soluble 

 chloride. The chloride of lead is soluble in 135 times its weight 

 of cold water, and more so in hot water, from which it crystal- 

 lizes in cooling in long flattened acicular crystals, which are an- 

 hydrous. The chloride of lead is very fusible, and may be 

 sublimed at a higher temperature. It combines in several pro- 

 portions with oxide of lead. The bibasic chloride of lead, PbCl 

 + 2PbO, is a colourless crystalline mineral, found at Mendip in 

 Somersetshire. The tribasic chloride of lead, PbCl + 3PbO-f 

 4 HO, is a white insoluble powder that falls when ammonia is 

 added to a solution of chloride of lead. It contains 7 per cent of 

 water (Berzelius). A surbasic chloride of lead, PbCl + 7PbO, 

 is produced on fusing by heat a mixture of 10 parts of pure 

 oxide of lead, and 1 part of pure sal ammoniac, a portion of the 

 lead being at the same time reduced. The surbasic chloride fused 

 affords cubic crystals, on cooling slowly. It forms in that state 

 a beautiful yellow pigment, known as Turner's yellow in this 

 country, and Cassel yellow in Germany. It was prepared 

 in England by digesting litharge with half its weight of com- 

 mon salt, a portion of which is converted into caustic soda, and 

 afterwards washing and fusing the oxichloride* formed. But it 

 is sufficient to use 1 part of salt to 7 parts of oxide of lead in 

 this decomposition. 



Iodide of lead, Pb I, 2874 or 230.3. Appears as a beautiful 

 lemon yellow powder, when iodide of potassium is added to a 

 salt of lead. It is soluble in 194 parts of boiling water, and in 

 1235 parts of water at the usual temperature, and may be ob- 

 tained from solution in brilliant hexagonal scales of a golden 

 yellow colour. A compound of a paler yellow, which appears 

 in dilute solutions, and when the salt of lead is in excess, is a 

 basic iodide. M. Denot finds three basic iodides of lead, con- 

 taining to 1 eq. of iodide of lead, 1 eq., 2 eq. and 5 eq. of oxide of 

 lead, and always 1 eq. of water, which last they do not lose below 

 a temperature of about 400. 



Cyanide of lead, Pb Cy, is a white insoluble powder, obtained 

 by precipitation. 



