CHEMICAL AFFINITY. 2T 



4. This kind of action is quite distinct from simple 

 mixture. When we mix together two substances — 

 such as, for example, brown sugar and sand, no change 

 takes place, however long they are kept together, or 

 in whatever way they are treated, for they have no 

 affinity or attraction for each other; and, therefore, 

 if boiling water is poured upon the mixture, it will 

 soon dissolve out all the sugar and leave the sand, 

 and neither the sugar nor the sand will be at all 

 altered by having been mixed. 



5. When we mix two substances which have an 

 attraction for each other, they are both changed, and 

 the new substance formed by their union is quite dif- 

 ferent from either ; and when two substances are thus 

 united or combined together, they are not so easily 

 separated as when merely mixed, because they require 

 the exertion of some attraction more powerful than 

 that which made them combine, to cause their sepa- 

 ration. In the case of the soap just mentioned, the 

 compound of fat and alkali does not resemble either 

 of its components ; it is different from the ley in not 

 being caustic, and differs from the fat in being easily 

 soluble in water. 



6. It is a rule which holds good in all cases, that 

 whenever two substances combine or unite together, 

 and form a new substance, the properties of the new 

 substance are quite different from those of either of 

 its components; but when two substances are only 

 mixed, the properties of the mixture are intermediate, 

 or half-way, between those of its two components : 



