EVIDENCE FOR THE EXISTENCE OF HYDRATES. 



19 



It 

 ft 

 tt 



6H 2 



Temperature of 

 crystallization. 



20 

 15 

 21 



21 to 37 

 -48 



to 2.7 

 5 

 20 



25 to 31, as a crust 

 25 to 31 

 15 to 20 

 or below 6 

 58 and above 

 -16 

 27 

 56 to 91 

 22 to 56 

 29 to 22 

 At ordinary temperatures 

 About to 10 

 20 to 24 

 2 to 20 

 8 to 2 



Ordinary temperatures 

 -10 to 18 

 Ordinary temperatures 

 -18 

 -9 

 27 



80 and above 

 60 to 80 

 40 to 60 

 20 

 20 to 16 



While there is a much larger number of cases on record where water of 

 crystallization varies with the temperature, in many of them the tempera- 

 tures at which the different amounts of water of crystallization were found 

 are either not given at all, or are given only approximately. Such cases, 

 in their present state, are of comparatively little value as bearing on the 

 problem under discussion. 



The examples given above suffice to show the general nature of the rela- 

 tion between water of crystallization and the temperature at which the 

 salt was crystallized. Work is now in progress on this point, and we hope 

 to find a much larger number of instances where temperature affects water 

 of crystallization; and, if possible, to establish even more marked effects 

 of temperature on the amount of water with which the salt crystallizes. 



