36 Historical Sketch uf Improvements in [JuLV, 



that the proposition is generally true, though I am not quite 

 certain that it holds so universally as Gay-Lussac seems to think 

 it does. 1 see no absurdity in supposing that the force of aggre- 

 gation in certain salts may be too strong to be overcome without 

 the assistance of heat, yet after it is once overcome, and the 

 salt dissolved, the particles of it in the liquid may be at so great 

 a distance from each other as not to unite together, and conse- 

 quently to remain in solution in cold water. I do not indeed 

 know any instance of this, though i think it very likely that some 

 one or other will occur whenever the solubility of all the salts at 

 different temperatures is investigated. 



Gay-Lussac has given us ample details respecting the solubi- 

 lity of nine different salts in water of every temperature from 32° 

 up to the boiliiig point of the saline solution. These solubihties 

 he has represented in a plate, to which I refer the reader for 

 ample satisfaction on the subject. 



Of all these salts the least soluble is sulphate of potash. 

 Water at 32° dissolves about 3-25 per cent, and boiling water 

 dissolves about 25^ per cent. 



The most equably soluble salt in water of different tempera- 

 tures is common salt. Water at 32° dissolves about 36-1- per 

 cent. ; while boiling water dissolves about 40 per cent. 



The most singular salt in point of solubility is anhydrous sul- 

 phate of soda. It is most soluble in water of the temperature 

 91i°, as the temperature of the water increases beyond that 

 point, the solubility of the salt slowly diminishes. Water at the 

 temperature of 32° dissolves 5 per cent, of the salt ; water at the 

 temperature 91^-° dissolves 50^- cent.; while boihng water 

 dissolves only 42 J- per cent. 



The nitrate of potash is the salt whose solubility increases at 

 the greatest rate with the temperature. Water at 32° dissolves 

 only 12 per cent, of it ; while water at 118^-° dissolves 80 per 

 cent, of it. 



The rate of the solubihty of sulphate of potash, common salt, 

 muriate of potash, muriate of barytes, and sulphate of magnesia, 

 is represented by a straight hne inchned at different angles to 

 the axis according to the increase of solubility with the tempera- 

 ture. 



The rate of the solubility of nitrate of barytes, chlorate of 

 potash, sulphate of soda, and nitrate of potash, is represented by 

 a curve convex towards the axis ;* and in sulphate of soda there 

 is a point of contrary ffexuve corresponding to the temperature 

 of 9\4r°, where the solubility of the salt is a maximum. 



Gay-Lussac has given the equation of the line of solubility in 

 several of the sali.s, and has shown the method of determining 

 that equatioii. For the details, I refer to tiie paper with which 

 my readers are doubtless acquainted. 



2. I have inserted in the Annals of Philosopky, xv. 90, a set 

 of analvses .of .vanious salts made bv Berzelius, with all the care 



