H. L. Wells — Double Salts of Lead Tetrachloride. 181 



Laps this is the formula of the compound, but they put a 

 question-mark after it. Their analysis indicates the existence 

 of PbCl 4 in combination with NaCl, but if the solution had 

 contained a compound of that composition, which was stable 

 with water, it probably could have been isolated by evapora- 

 tion. The fact is that the double salts of lead tetrachloride are 

 not stable with water, as will be shown in the present article. 

 Therefore, since a large excess of sodium chloride must have 

 been present in the solution of Sobrero and Selmi, their analy- 

 sis could not have determined the composition of the double 

 salt that it contained. 



Nickles* saturated a strong solution of calcium chloride with 

 lead chloride and chlorine and analyzed the solution. He 

 found it to contain lead, calcium and chlorine in the propor- 

 tions represented by PbCl 4 -r-16CaCl 3 . In conclusion Nickles 

 does not claim that any such double salt exists, but merely 

 claims to have indicated the existence of PbCl 4 . 



In view of the fact that the formulae PbCl 4 +9NaCl and 

 PbCl 4 +16CaCl, merely represented the composition of solu- 

 tions, it is remarkable that they are given in some handbooks 

 of chemistry as real chemical compounds. It may be men- 

 tioned that Carnegief has used the formula PbCl 4 . 9NaCl in 

 support of a theory on double halides. 



O. Seidell mentions unsuccessful attempts to isolate PbCl 4 

 and its double salts with the chlorides of other metals. 



Fisherg dissolved lead peroxide in hydrochloric acid and 

 found that all the lead in the solution was precipitated again 

 as peroxide by the addition of sodium acetate. He was evi- 

 dently not aware of the fact that Rivot, Beudant and Daguin] 

 had shown, long before, that lead is completely precipitated as 

 peroxide by the addition of sodium acetate and chlorine to its 

 solutions. Fisher found that two atoms of chlorine were used 

 (as would be expected) in precipitating one atom of lead as 

 peroxide. His conclusion that his experiments showed the 

 existence of lead tetrachloride has, apparently, little foundation. 



More recently, Dittelj has made some experiments on the 

 solubility of lead chloride in solutions containing hydrochloric 

 acid and chlorine. He apparently does not believe in the exist- 

 ence of lead tetrachloride, for he does not mention the com- 

 pound, while he explains the precipitation of lead peroxide, 

 when such solutions are diluted, by saying that lead chloride 

 is partly dissociated by the act of solution, that the solution 

 then contains oxide of lead, and that this is peroxidized by the 



* Ann. Chim. Phys., IV, x, 323. + Am. Chem. Jour., xv, 10. 1893. 



t Jour, pr. Ch., II, xx, 205, 1879 $ Jour. Chem. Soc, xxxv, 282, 1879. 



I Ann. Mines, V, iv, 239, 1853. r Ann. Chim. Phys., V, xxii, 566, 1881. 



