GO 



and solids increpse it. A saturated solution of salt boils at io2°C., and 

 one of calcium chloride at i79°C. 



Several other factors have been noticed to influence the boiling 

 point, e.g;., the quantity of water used and the material composing the 

 vessel in which it is heated. Single drops of water suspended in other 

 liquids have been heated many degrees above this i)oint before they 

 suddenly transformed into a volume of steam. In a perfectly clean 

 glass vessel, water has been heated to to6°C. before ebullition com- 

 menced. Together with the first bubble, however, sufficient steam was 

 generated to reduce the temperature to the normal boiling point. This 

 cause of " bumping " may be overcome by placing a piece of metal in 

 the bottom, of the flask. 



The value of water ?s an extinguisher of fire is partially dependent 

 upon the large amount of of heat absorbed when transformed to steam 

 and partially upon the fact that it serves to prevent the oxygen of the 

 atmosphere from coming as readily in contact with the burning material. 

 Combustion of such substances as wood and coal is dependent on their 

 union with oxygen, and this does not take place to such an extent as 

 to cause what is known as burning, unless they are heated to a consider- 

 able degree. 



Although taking place more quickly when boiling, we know that 

 water can evaporate at any temperature between the boiling and the 

 freezing points, in fact considerably below the latter. Ice will evaporate 

 on a cold winter day as clearly shown by clothes drying at such a time. 

 We might therefore be almost justified in saying that we could boil ice. 

 This term is, however, only applied to liquids, and only when the vapour 

 is formed throughout the mass and rises as bubbles to the surface. 

 When this is not the case we speak of liquids as evaporating and solids 

 as volatilizing. The singing noise sometimes heard in water shortly 

 before it reaches the boiling point is produced by the formation and 

 subsequent collapsing of bubbles of steam. 



As in melting ice, the heat rendered latent in vaporization is 

 expended in changing the relation of the molecules to each other. 

 These arc much further apart in steam than in water. One volume of 

 the latter would occupy nearly 1700 volumes when converted into the 



