72 THE ATOMIC WEIGHTS. 



LEAD. 



For the atomic weight of lead we have to consider experi- 

 ments made upon the oxide, chloride, nitrate, and sulphate. 

 The researches of Berzelius upon the carbonate and various 

 organic salts need not now be considered, nor is it worth 

 while to take into account any work of his done before the 

 year 1818. The results obtained by Dobereiner* and by 

 Longchampt are also without special present value. 



For the exact composition of lead oxide we have to de- 

 pend upon the researches of Berzelius. His experiments 

 were made at different times through quite a number of 

 years ; but were finally summed up in the last edition of 

 his famous " Lehrbuch."| In general terms his method of 

 experiment was ver}^ simple. Perfectly pure lead oxide was 

 heated in a current of hydrogen, and the reduced metal 

 weighed. From his weighings I have calculated the per- 

 centages of lead thus found and given them in a third 

 column : 



Mean, 92.8271, rz .0013 



For the synthesis of lead sulphate we have data by Ber- 

 zelius, Turner, and Sta§. Berzelius,|| whose experiments 



*Schweig. Journ., 17, 241. 1816. 

 f Ann. Chim. Phys., 34, 105. 1827. 

 + Bd. 3, s. 1218. 

 II Lehrbuch, 5th Ed., 3, 1187. 



