RICHARDS AND MARK. — EXPANSION OF GASES. 



427 



Since the temperature of the sodic sulphate is referred to tlie inter- 

 national hydrogen scale, — that is, to the increase in tension of hydrogen 

 at constant volume, — this series of results is merely a comparison 

 between the thermal coefficient of hydrogen at constant volume and that 

 at constant pressure. 



A mixture of ninety-eight per cent of nitrogen and two per cent of 

 hydrogen had the following coefficient of expansion : 



IMPURE NITROGEN. 



Carbon dioxide made by the action of hydrochloric acid on marble, 

 and purified by passing through acid sodic carbonate solution, sulphuric 

 acid and over phosphoric oxide, gave the following results: 



CARBON DIOXIDE. 



