LECTURE IV 



CHEMICAL AFFINITY HEAT 



WE shall have to pay a little more attention to the 

 forces existing in water before we can have a 

 clear idea on the subject. Besides the attraction 

 which there is between its particles to make it hold to- 

 gether as a liquid or a solid, there is also another force, 

 different from the former one which, yesterday, by means 

 of the voltaic battery, we overcame, drawing from the water 

 two different substances, which, when heated by means of 

 the electric spark, attracted each other, and rushed into 

 combination to reproduce water. Now I propose to-day to 

 continue this subject, and trace the various phenomena of 

 chemical affinity ; and for this purpose, as we yesterday con- 

 sidered the character of oxygen, of which I have here two 

 jars (oxygen being those particles derived from the water 

 which enable other bodies to burn), we will now consider 

 the other constituent of water, and, without embarrassing 

 you too much with the way in which these things are made, 

 I will proceed now to show you our common way of making 

 hydrogen. (I called it hydrogen yesterday: it is so called 

 because it helps to generate water.)* I put into this retort 

 some zinc, water and oil of vitriol, and immediately an 

 action takes place, which produces an abundant evolution of 

 gas, now coming over into this jar, and bubbling up in 

 appearance exactly like the oxygen we obtained yesterday. 



The processes, you see, are very different, though the 

 result is the same, in so far as it gives us certain gaseous 

 particles. Here, then, is the hydrogen. I showed you yester- 

 day certain qualities of this gas; now let me exhibit you 

 some other properties. Unlike oxygen, which is a supporter 

 of combustion and will not burn, hydrogen itself is com- 



* viwp, " water," and ytwow, " I generate." 



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