436 LAWSON CHEMICAL RELATIONS OF HEAT. 



Art. XIIl. — Chemical Kelations of Heat. With Experi- 

 ments. Br Professor Lawson, Ph. B., L. L. D., 



Dalhousie College. 



He explained the nature of heat a^ a form of force, co-relative 

 with light, mechanical energy, electricity, magnetism, and chemical 

 affinity, showing the one to be convertible into the other. These 

 forces influence matter ; upon the varying degrees of heat depends 

 the condition of matter, whether it exists as a solid, a liquid, 

 or a gas. Water is solid at low temperatures, when we give it 

 more heat, raising the temperature to 32°, it becomes a mobile 

 liquid; if the .temperature be raised to 212°, the water has its 

 condition changed to that of an invisible gas, which we commonly 

 call steam. As soon as the excess of heat above 212° is removed, 

 the gas (or steam) passes back into the liquid state, and then if 

 further reduced (below 32°) into a solid, which is the present 

 condition of all surface water in this part of the world, except 

 in the deep sea or in deep lakes, &c., where it has not been cooled 

 down to that temperature. In still waters, however, a foot or 

 tvv^o of the surface forms our ice-bridges and skating ponds). 



Illustrations were given to show that when a liquid passes into 

 a gaseous state it absorbs heat, which it necessarily takes from 

 surrounding bodies, and makes them cold. Ammonia, ether, alcohol, 

 vinegar, all readily volatilise, pass into the gaseous state, and the 

 absorption of heat, to enable them to do so, necessarily produces a 

 sensation of cold on the skin. The most remarkable body shown 

 was sulphur dioxide, which, when poured on the back of the hand, 

 evaporates instantaneously, produces intense cold, and freezes the 

 flesh if used in too great quantity. The freezing of the hand in 

 this way presents all the uncomfortable and dangerous symptoms 

 of natural freezing at an excessively low temperature in an extreme 

 climate. The evaporation of sulphur dioxide in a current of air 

 produces a still lower temperature, freezing mercury, which does 

 not solidify till the temperature goes down to 39° below zero. 

 All these temperatures are of the Fahrenheit scale, the only one 

 known in Nova Scotia except in scientific laboratories, where the 

 Centigrade system is coming into use, and must in time prevail. 



