Academy of Science. 



21 



its getting at all — even a fraction of a degree — above the desired point, in order that 

 guper-saturation may be absolutely impossible. 



At the end of one half-hotir (or longer, if necessary) at that temperature, the machine 

 is stopped and allowed to remain quiet ten or fifteen minutes, that the crystals may settle; 

 the tube d d being turned at such an angle that the end h is in clear liquid, and not in 

 the vicinity of crystals. A drawing is then made in the following manner: The piston f> 

 is drawn out until the opening o is cleared. One person blows into the bottle through 

 the tube c c and its rubber attachment, at the same time pressing the clamp /, while 

 another holds a tarred beaker provided with a ground-glass cover (the beaker itself 

 having a ground edge) under the orifice o until the proper amount of solution is obtained. 

 The ground-glass cover is quickly placed on the beaker, the whole is allowed to cool, and 

 is then weighed. The amount of salt dissolved in that amount of solution is then deter- 

 mined by the most reliable and convenient method. 



Parallel determinations were always made, the second drawing being made about one 

 qftarter-hour after the first, the bottle meantime having been kept in revolution, and the 

 temperature constant. The determinations were made usually at intervals of 10° C, 

 ranging from 0° or 10° to 90° or 100°. 



In this way the solubilities of salts have been determined, both singly (one salt alone 

 in water), and mixed (two salts, both present in excess of the solvent), with uniformly 

 gratifying results, the curves being in each case more regular than any previously 

 obtained ; and all the results, with very few exceptions, show upon comparison with those 

 on record, obtained by the old method of work, smaller amounts of salt dissolved at the 

 respective temperatures — a fact which goes far to prove that super-saturation has, in 

 some cases at least, been a vitiating element in the work. 



We give below the curve for the solubility of anhydrous cupric sulphate (Cu S04,) 

 based upon the figures obtained by us, representing the number of parts of the anhydrous 

 salt soluble in one hundred parts of water. We also give for comparison the figures 

 actually obtained for the same salt, showing the magnitude of the discrepancies between 

 parallel determinations. 



We should state however, that in this curve the figures for 0° and 100° were obtained 

 with the utmost care by our method of work (raising the temperature, not lowering it), 

 but not with aid of the apparatus — flasks having been used instead. This work was per- 

 formed at the laboratory of Cornell University, and we owe many thanks to Prof. C. H. 

 Wing, non-resident Professor of Chemistry at Cornell, for his kind and valuable sug- 

 gestions regarding it. 



Parts Cu SO4 (anhyd.) soluble in 100 parts water. 



At 0°C 13.98 



AtlO°C 17.34 



At 20° C 20..58 



At 30° C 24.37 



At40°C 28.50 



At 50° C 33.34 



At 60° C 39.00 



At 70° C 45.61 



At 80° C 54.63 



At 90° C 63.50 



At 100° C 75.18 



