72 ATOMIC WEIGHT DETERMINATIONS. 



nitric acid and evaporation with sulphuric acid. In three 

 experiments, Turner found 100 lead = 146.401 sulphate ; 

 extreme difference 0.055. Berzelius had found 100 Pb = 

 146.419 sulphate ; extreme difference 0.078. Turner takes 

 the mean of his own and Berzelius' determinations, 146.41. 

 In one experiment Turner found 100 oxide = 135.92 sul- 

 phate. Combination of these results gives Pb = 103.6 [or 

 more accurately 103.65.] The oxide was prepared from 

 subnitrate. The lead was prepared from plumbic acetate 

 which was converted into carbonate, then into nitrate, in 

 which form it was recrystallized, then again into carbonate^ 

 and reduced by black flux. On testing, it was found per- 

 fectly pure. Weighings reduced to vacuum. [Phil. Trans. y 

 123, 1833, 524.) 



C. Marignac : 207.04 (0 = 16). 



Marignac made four experiments on plumbic chloride by 

 Pelouze's modification of the silver titration method. He 

 found Pb = 103.57-.49-.55-.46. The number taken is the 

 mean. The salt was titrated cold, argentic chloride being 

 soluble in hot solutions of plumbic nitrate. The plumbic 

 chloride was purified by recrystallization, and, after being 

 pulverized, was dried at about 200°. According to Marig- 

 nac there is no difficulty in desiccating it completely at this 

 temperature. Ag = 108 ; 01 = 35.5. Marignac found it 

 impossible to convert the chloride into the sulphate com- 

 pletely. {Bibl. Univ., Arch, des Sciences, (2,) 1, 1858, 223.) 



J. Dumas : 207.1 (0 = 16). 



From a single experiment on the precipitation of the 

 chloride with argentic nitrate. The chloride used wa& 

 heated for twelve hours in a current of dry HOI, and the 

 amount of water retained determined. Dumas found it im- 

 possible entirely to desiccate the salt without decomposition,, 

 drying at 250° does not desiccate it. 01 = 35.5 ; Ag = 108. 

 {Annal. de Chim. et de Phys., (3,) 55, 1859, 129.) 



J. S. Stas: 206.926 (0 = 16). 



According to the mean of 10 syntheses of plumbic nitrate, 

 100 lead = 159.9703 nitrate; extreme difference, 0.023. If 

 1^= 14.044, this relation gives Pb = 206.918. Stas also 

 made six syntheses of the sulphate, which gave in mean 

 100 Pb = 146.4275 sulphate ; extreme difference, 0.024. If 

 S = 32.0742, this relation gives Pb = 206.934. The syntheses 

 were made in the same way as in the determination of the 



