xvi ATOMIC WEIGHTS OF THE METALS 379 



The composition of chalk is therefore : 



f LIME, 5-64 grams= - f 



CHALK, ,o grams = CARBONIC ANHYDRIDE }8, % * " 



I 4-36 grams = \CARBON... 1*24 ,, 



The oxygen in the acid is seen to be double the amount 

 in the base, as in the case of the sulphites. 

 The proportions of the three elements are : 



Formula CaCO,,. 



4. Lead Nitrate. Berzelius found that 



(1) 20 grams of dry, powdered lead nitrate, ignited in a 

 weighed platinum crucible, left 13*445 grams of oxide ; 

 therefore 100 grams of the salt contain 67*22 grams of lead 

 oxide, composed of 4*85 grams of oxygen and 62'37 grams 

 of lead (Klassiker, XXXV. 129). 



(2) Gay-Lussac had proved (p. 203) that nitric anhydride 

 was composed of 2 volumes of nitrogen of density 0*969 and 

 5 volumes of oxygen of density 1*104 ( a i r = ' the com- 

 position by weight was therefore 0*969 x 2 : 1*104 x 5 = 

 i "938 : 5*520. The weights of the two gases in 100 - 67*22 = 

 32*78 grams of nitric anhydride are therefore 



f x 32*78= 8 '52 grams of nitrogen 

 and 32*78 - 8*52 = 24 '26 grams of oxygen. 



From these analyses it is clear that the composition of 

 the salt is : 



( LITHARGE, ^LEAD 62*37 grams 



LEAD NITRATE, J 67^22 grams = \OXYGEN... 4*85 



ANHYDRIDE, fOXYGEN... 24*26 



32 '78 grams = \ NITROGEN 8*52 



ioograms= | NITRIC ANHYDRIDE, | OXYGEN... 24-26 



