74 



SMITH S INTERMEDIATE CHEMISTRY 



however, for the volume which is the standard or unit in chemistry. 

 This is the volume occupied by 32 grams of oxygen, which is 22.4 

 liters at and 760 mm. This volume is equal to that of a cube 

 about 11 inches in height (Fig. 36). At other temperatures and 

 pressures this volume, in order to contain the same amount of 

 material, alters its value, in accordance with the laws of Boyle and 

 Charles (p. 45). The reason for selecting this particular volume 

 will be readily seen, so soon as we shall have 

 presented 'the actual weights of various 

 materials which fill it. 



22 4 LITERS The Weights Filling the Unit Vol- 



ume, 22.4 Liters. The following table 

 contains a few sample substances, and gives 

 FlG 36 the weight (in grams) of each which, in the 



gaseous condition, at and 760 mm., 



occupies the cube 22.4 liters. In the cases of compound sub- 

 stances, like water, we have given also the weights of the constituent 

 elements which together make up the total weight of the com- 

 pound filling the unit volume: 



WEIGHTS OF GASES IN 22.4 LITERS (AT AND 760 MM.). 



The first column (" Total wt.") gives the number of grams of each 

 substance occupying, as a gas, 22.4 liters at and 760 mm. This 

 is the standard or unit weight of that substance. In the case of 

 water, which is a liquid at room temperatures and pressures, a 

 known volume of steam is weighed. The volume is reduced by 



