﻿Acetylene. 115 



when it is burnt becomes evident and is measured, when 

 we find that the acetylene arrangement or combination of 

 carbon and hydrogen atoms is capable of making the 

 elements do more work, that is to heat 71 kilograms 

 more water than when the same elements are free in the 

 state of amorphous carbon and of hydrogen gas. 



When the carbon from carbide of calcium and hydrogen 

 from water combine to make acetylene heat is utilized in 

 changing the carbon from the solid and the hydrogen 

 from the liquid form to the form of a gas. Heat is ab- 

 sorbed in this process which imparts a new energy of 

 motion to the atoms, in the same way that heating water 

 separates the particles to two thousand times wider dis- 

 tances from each other and gives them the energy of 

 motion which is apparent in steam. In this case we can 

 measure the amount of heat required for this work and 

 which is absorbed while it takes place. Unfortunately 

 we can not get similar measures with carbon vapour and 

 solid carbon, and we can only measure a total absorption 

 of heat during the generation of acetylene, and we sup- 

 pose that the total, 71 heat units, may be made up by the 

 absorption of a larger amount of heat in order to change 

 amorphous carbon to the gaseous state, from which must 

 be deducted the heat which is given out when two carbon 

 and two hydrogen atoms combine to make C^H.^. Ben- 

 zene which has exactly the same percentage of carbon 

 and hydrogen, but combined into quite a different chemi- 

 cal group, shows that more energy has been expended in 

 bringino- about its chemical arrans^ement. The sio^ns 

 which attest this are greater stability, smaller chemical 

 activity, and above all the fact that when benzene is 

 burnt it gives off much less heat than the same weight of 

 acetylene does, and in fact only 4 heat units more than 

 the same weight of carbon and of hydrogen. 



It has seemed necessary to explain fully how quanti- 

 ties of energy, which can usually be measured in terms 



