126 VOLUMES OF ATOMS IN THE GASEOUS STATE. 



Sulphate of lime . . 0.1854 . 0.1412 



Sulphate of strontian . . 0.1300 . 0.1326 

 Sulphate of lead . . 0.0830 . 0.1398 



Mean . 0.1380 



The numbers in the second column of both tables, deviate 

 very little from their mean, but there is no relation between 

 the two means. Identity in capacity for heat is, therefore, to 

 be looked for in compound atoms of the same nature, and 

 which closely agree in their chemical relations, like the num- 

 bers of each group, but not between compound atoms which 

 are differently constituted. 



RELATION BETWEEN THE ATOMIC WEIGHTS AND VOLUMES OF 

 BODIES IN THE GASEOUS STATE. 



Several of the elementary bodies are gases, such as oxygen, 

 hydrogen, nitrogen and chlorine, and the proportions in which 

 they combine can be determined by measure with equal, if 

 not greater facility than by weight. A relation of the simplest 

 nature is always found to subsist between the measures or vo- 

 lumes in which any two of the gaseous elementary bodies unite. 

 This arises from the circumstance that the specific gravities of 

 gases either correspond exactly with their atomic weights, or 

 bear a simple relation to them. The atom of chlorine is 35J 

 times heavier than that of hydrogen ; and chlorine gas is also 

 35j times heavier than hydrogen gas, so that the combining 

 measures of these two gases, which correspond with single 

 equivalents, are necessarily equal. The atom of nitrogen, and 

 its weight as a gas being both 14.2 times greater than the atom 

 and weight of hydrogen gas, their combining volumes must be 

 the same. The atom of oxygen is eight times heavier than that 

 of hydrogen, but oxygen gas is sixteen times heavier than hy- 

 drogen gas, so that taken in equal volumes these two gases are 

 in the proportion by weight of two equivalents of oxygen to 

 one of hydrogen. Hence, in the combination of single equi- 

 valents of these elements to form water, half a volume or mea- 

 sure of oxygen gas unites with a whole volume or measure of 

 hydrogen gas. One volume of nitrogen, also unites with half 

 a volume of oxygen, and with a whole volume of the same gas, 

 to form respectively the protoxide and deut oxide of nitrogen. 



The exact ratio of one to two in which oxygen and hydrogen 



