DISCUSSION OP THE RESULTS. 137 



as to the way in which these substances break down into ions are not in 

 accord with the facts. As these matters have already been discussed at 

 sufficient length they need only be referred to in the present connection. 



Potassium hydroxide, like sodium hydroxide, shows considerable power to 

 form hydrates. As with sodium hydroxide, the composition of the hydrates 

 passes through a minimum. These hydroxides have considerable power to 

 crystallize with water at low temperatures. 



The double chloride of potassium and copper has great power to combine 

 with water in aqueous solutions. This salt, like the other double halides, as 

 was shown by Jones and Knight,* breaks down in the presence of water, for 

 the most part, into the constituent chlorides. The hydrating power of the 

 above double chloride is essentially the hydrating power of copper chloride, 

 which will be discussed a little later. 



The salts of ammonium resemble the salts of sodium and potassium, in 

 that they crystallize without water, and have very small power to combine 

 with it in aqueous solution. (See tables 29 to 33.) 



The freezing-point data are plotted in curves, figs. 3, 4, 5, 14, and 17, 

 the conductivity data in figs. 7, S, and 9, the refractivities in figs. 12 and 13, 

 and the hydrates of ammonium copper chloride in fig. 55, and of ammonium 

 hydroxide in fig. 57. 



The same remarks apply to the double chloride of ammonium and copper, 

 that were made concerning the double chloride of potassium and copper. 

 The large hydrating power of both of these salts is due primarily to the 

 copper chloride, which is formed as the result of the action of water on these 

 double halides. 



Ammonium hydroxide, like the hydroxide of sodium and potassium, 

 shows very considerable power to combine with water in aqueous solution. 



The salts of calcium, that were brought within the scope of this work, all 

 crystallize with comparatively large amounts of water, and all of them have 

 large hydrating powers. The results are given in tables 34 to 37, and the 

 freezing-point data plotted as curves in figs. 3, 14, 15, 17, 19, 21, and 28. 

 The conductivity data are plotted in figs. 7, 22, and 29, the refractivities in 

 fig. 23, and the hydrates in figs. 46 and 48. The hydrates formed by calcium 

 chloride, bromide, and iodide increase in complexity with the dilution of the 

 solution. This is shown, with very few irregularities, especially by calcium 

 chloride. The hydrating power of these three substances is of the same order 

 of magnitude, as would be expected from their power to combine with water 

 as water of crystallization. 



Calcium nitrate crystallizes with only four molecules of water, and has less 

 hydrating power than the halides of calcium, just as would be expected. 



The salts of strontium resemble in their water of crystallization, and in 

 their hydrating power, the corresponding salts of calcium. 



*Amer. Chem. Journ., 22, 110 (1899). 



