SECT. II.] 



PROPERTIES OF STEAM. 



79 



with the least range of temperature above the one convenient for condensation : to 

 a vapour of this kind, heat may be applied without requiring so extensive a surface 

 for the fire to act on as when water is used. 



On the other part, a fluid which has a low elastic force at a high temperature 

 may sometimes be conveniently and safely applied to afford a regular heat to the 

 acting vapour ; hence, it becomes difficult to say to what objects it is improper to 

 extend our inquiries. 



Mr. Dalton made some experiments on the vapour of ammonia. The ammonia 

 he used boiled at 140 ; and its specific gravity was '9474. It had a force of 4'3 

 inches at 60 ; but on increasing the temperature, the volatile parts separated first, 

 and left the rest with a greater proportion of water, requiring a still higher tem- 

 perature to convert them into steam : this fluid is therefore inapplicable. 



113. The force of the vapours of petroleum, and of oil of turpentine, has been 

 ascertained by Dr. Ure : the following tables contain his results : 



EXPERIMENTS ON THE FORCE OF VAPOUR OF PETROLEUM, * OR NAPHTHA. 



EXPERIMENTS ON THE FORCE OF THE VAPOUR OF OIL OF TURPENTINE. 



For the steam of petroleum, the boiling point being 316, the rule in logarithms is 



log./ = 6 (log. (t + 100) - 2-37291). 

 For the steam of oil of turpentine, which boils in a tube at 304, the rule in logarithms is 



log./ = 6 (log. t + 100) - 2-36019 ). 



