Heat as a Quantity 173 



vessels may be substituted, but these are not necessary 

 unless a fairly high degree of accuracy is desired in 

 the results obtained. Vessels such as the beakers and 

 copper cans, when made use of in the measurement 

 of quantities of heat, are termed " calorimeters " 

 (Latin, color, heat). 



111. A striking experiment showing the great 

 amount of heat absorbed during the evaporation of 

 a liquid may be performed with the readily volatile 

 and extremely inflammable liquid, ether. This experi- 

 ment must not on any account be attempted in the 

 neighbourhood of flames, and is best done by, or under 

 the immediate supervision of, a teacher. 



EXPERIMENT 59. Into a small beaker pour enough 

 ether to fill it one- quarter full. Let about six drops 

 of water fall on the middle of one face of a small wooden 

 block. Put the beaker on the block in contact with 

 the water. Blow air through a glass tube attached 

 to a bellows, worked by hand or by the foot, by means 

 of rubber tubing, the end of the tube being made to 

 dip under the surface of the ether. The rapid bubbling 

 thus produced causes a large surface of ether to be 

 exposed, and greatly increases the rate at which the 

 liquid evaporates. Since no heat is supplied from an 

 outside source, that required for the conversion of the 

 ether from the liquid to the gaseous state must be taken 

 from the ether and the bodies in contact with the ether. 

 As a result, these bodies, i.e. the beaker, water, and 

 block, have their temperatures reduced considerably. 

 By steady blowing it is easy to lower the temperature 

 of the water to 0, and continuance of the operation 

 causes the formation of ice, the beaker being frozen 

 to the wooden block. 



