/i ATOMIC WEIGHTS OF THE METALS 375 



(1) 10 grams of lead, dissolved in nitric acid and ignited, 

 gave 1078 grams of the oxide (litharge). 



(2) 10 grams of lead, when fused with sulphur, gave 1 1*56 

 grams of sulphide. 



(3) Io grams of lead sulphide, when digested with aqua 

 regia, gave 12*65 grams of sulphate, no excess of lead or of 

 sulphuric acid being left uncombined. 



(4) 10 grams of lead, dissolved in nitric acid and pre- 

 cipitated with sulphuric acid, gave 14*635 grams of lead 



sulphate, in close agreement with the weight -*-^ 5 



10 



= 14*623 grams calculated from (2) and (3). 



From these experiments Berzelius concluded : 



(5) That lead and sulphur in lead sulphide are combined 

 together in exactly the same proportions as when their 

 oxides unite to form lead sulphate. 



(6) That 10 grams of lead sulphide in forming lead 

 sulphate unite with 2*65 grams of oxygen ; the 10 grams of 



sulphide contain IQO = 8*651 grams of lead, yielding on 

 11*56 



oxidation ^ r x IO ' = 9*326 grams of lead oxide, thus 

 10 



accounting for 9*326 - 8*651 = 0*675 gram of oxygen ; the 

 remainder, 2*65 - 0*675 = r 975 of tne oxygen in the 

 sulphate was therefore combined with 10 - 8*651 = 1*349 

 grams of sulphur to form 3*324 grams of sulphuric anhy- 

 dride. The composition of sulphuric anhydride was there- 

 fore : 



Sulphur 1*349 grams = 40'58% 

 Oxygen 1*975 grams = 59*42% 



i.e. sulphur : oxygen = 2:3 nearly. 



(7) In the sulphate, litharge containing 0*675 gram of 

 oxygen was combined with sulphuric anhydride containing 

 1*975 grams of oxygen. The weights of oxygen in the acid 

 and in the base were therefore in the ratio 3 : I, a ratio that 

 held good for the sulphates generally (Chemical Proportions, 

 1819, p. 122). 



