76 SCIENCE PRIMERS. [MATERIAL 



freezes at a much lower temperature than water 

 does, and at a higher temperature than alcohol does. 

 In fact pure alcohol has not yet been frozen. If the 

 molecules of the alcohol were merely diffused among 

 those of the water as w r ater is diffused through wet 

 sand, they ought to pass into the gaseous state at the 

 same temperature as that at which alcohol boils ; and 

 it would then be very easy to separate alcohol from 

 water by distillation. But the fact is not so ; alco- 

 hol cannot be obtained free from water by distillation 

 unless something which holds water very strongly, 

 such as quicklime, is added > so as to keep all the 

 water back when the fluid is heated. 



Thus alcohol and water, mingled together, give rise 

 to a fluid which is not a mere mixture, the properties 

 of which are known if we know the properties of its 

 components ; it is, in strictness, a new body, in which 

 the molecules of the water and those of the alcohol 

 affect one another to a certain extent, and modify the 

 pre-existing properties of each. 



This effect of different bodies upon one another 

 becomes much more manifest when water is brought 

 into contact with certain solids. 



53. Solution : Water Dissolves Salt. 



If a spoonful of salt is put into a tumbler of cold water 

 and the w r ater is stirred, the salt swiftly vanishes from 

 view ; and, after a time, so far as our sense of vision 

 goes, the water appears to be just what it was before. 

 But if the water in the tumbler at first weighed five 

 ounces and the salt weighed two ounces, the water 

 in the tumbler will now weigh seven ounces ; the 

 water will now taste salt, the salt is said to be 



