LEAD. / O 



The third column gives the ratio between PbCl,, and 100 

 parts of Ag- : 



4.9975 grin. PbCIj = 3.8S10 gi-m. Ag. 128.768 



4.9980 " 3.8835 " 128.698 



5.0000 " 3.8S35 " 128.750 



5.0000 " 3.8860 " 128.667 



Mean, 128.721, rh .016 



Dumas,* in his investigations, found that lead chloride 

 retains traces of water even at 250°, and is sometimes also 

 contaminated with oxychloride. In one estimation 8.700 

 grammes PbCL, saturated 6.750 of Ag. The chloride con- 

 tained .009 of impurity; hence, correcting, Ag : PbCL : : 

 100 : 128.750. If we assign this figure equal weight with 

 those of INIarignac, we get as the mean of all, 128.72G6, ± 

 .013. The sources of error indicated by Dumas, if they are 

 realh' involved in this mean, would tend slightly to raise 

 the atomic weight of lead. 



The .synthesis of lead nitrate, as carried out by Stas,t 

 gives excellent results. Two series of experiments were 

 made, with from 103 to 250 grammes of lead in each deter- 

 mination. Tlie metal was dissolved in nitric acid, the solu- 

 tion evaporated to dryness with extreme care, and the 

 nitrate weighed. All weighings were reduced to the vacuum 

 standard. In series A the lead nitrate was dried in an air 

 current at a temperature of about 155°. In series B the 

 drying was effected in vacuo. 100 of lead yield of nitrate : 



159 

 159 

 159 

 159 

 159 

 159 



973 

 975 

 9S2 



975 

 968 



.973 



Mean, 159.9743, rh .0012 



* Ann. Cham. Pharm., 113, 35. i86o. 

 f Aronstein's Translation, 326. 



