LEAD. 127 



LEAD. 



For the atomic weight of lead we have to consider experiments made 

 upon the oxide, chloride, nitrate, and sulphate. The researches of Ber- 

 zelius upon the carbonate and various organic salts need not now lie 

 considered, nor is it worth while to take into account an}' work of his 

 done before the year 1818. The results obtained by Dobereiner* and 

 by TiOngchamp f are also without special present value. 



For the exact composition of lead oxide we have to dej^end upon the 

 researclies of Berzelius. His experiments were made at different times 

 through quite a number of 3'ears ; but were finally summed up in the 

 last edition of his famous '' Lehrbuch."t In general terms his method 

 of experiment was very simple. Perfecth^ pure lead oxide was heated 

 in a current of hydrogen, and the reduced metal weighed. From his 

 weighings I have calculated the percentages of lead thus found and 

 given them in a third column : 



Earlier Results. 



8.045 S^"'"- ^^'^^ gz-vz 7-4675 gi'in. Pb. 92.8217 per cent. 



14.183 " 13-165 " 92.8224 



10.8645 " 10.084 " 92.8160 " 



13.1465 " 12.2045 " 92.8346 " 



21.9425 " 20.3695 " 92-S313 



II. 159 " 10.359 " 92-8309 



Latest. 



6.6155 " 6.141 " 92.8275 " 



14.487 " 13.448 " 92.8280 " 



14.626 " 13-5775 " 92S313 " 



Mean, 92.8271, =h .0013 



For the synthesis of lead sulphate we have data by Berzelius, Turner, 

 and Stas. Berzelius, § whose experiments were intended rather to fix 

 the atomic weight of sulphur, dissolved in each estimation ten grammes 

 of pure lead in nitric acid, then treated the resulting nitrate with sul- 

 l)huric acid, brought the sulphate thus formed to dryness, and weighed. 

 One hundred parts of metal yield of PbSO^: 



146.380 

 146.400 

 146.440 

 146.458 



Mean, 146.419, =b .012 



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

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

 X Bd. 3, s. 1218. 

 I Lehrbuch, 5th ed., 3, 11S7. 



