^Salts. 129 



tity it will dissolve no more. When the water 

 will dissolve no more, the point at which the 

 salts cease to dissolve is called, as was before 

 mentioned, the point of saturation. The pro- 

 portion of water is very different with respect to 

 different salts : some require only a quantity of 

 water equal to themselves .in weight. A satu- 

 rated cold solution dissolves more salt if a little 

 heat is thrown into it. Common salt is, how- 

 ever, one exception to this general rule ; it dis- 

 solves with equal ease in the same quantity of 

 cold water as in warm, Mr. Macquer thought 

 the deliquescent salts were also exceptions ; but 

 this remark is by no means just. We are not 

 agreed as to what salts are to be called deliques- 

 cent, and what not : their deliquescence may de- 

 pend sometimes on the particular dampness of 

 the air, and sometimes on their own particular 

 condition. 



From the phaenomena attending the dissolu- 

 tion of salt, Sir Isaac Newton thought that there 

 was an equal distribution of it through a deter- 

 mined space of water, and hence the deposition 

 is in a regular order ; hence also, if a space of 

 water is increased by expansion, it is capable of 

 arranging a greater number of particles of salt 

 than it otherwise would do. That something of 

 this kind really takes place is evident from expe- 

 riment, as that part of the water which contains 

 the least salt will have the greatest attraction for 

 it ; and thus the distribution of the salt will pro- 



G5 



