1908] 



on Ice and its Natural History. 



255 



Curves C and C^ refer to ice of which 9167 grams or 10,000 c.c. 

 at 0° C. contain 1*5105 gram NaCl. xibove the Z-like portion the 

 curve shows a maximum volume of 9992*834 c.c. at -2°* 3. At 

 temperatures liigher than tliis the coefficient of apparent expansion 

 is negative. 



In the same figure curves A and Aa represent the volumes of a 

 block of ice weighing 91*67 grams and containing 1*5105 gram 

 NaCl diffused through it. The line Aa represents its volume Y at 

 temperature f, the salt being inert ; at O'' the vohime is 100 c.c. 

 The curve A, after the Z-like portion, shows a maximum volume at 



- 20' '5, above which its apparent volume diminishes, as the tempera- 

 ture rises, and at - 1° *0 the ice is practically all melted. 



When 1*5105 gram NaCl is diffused in a block of ice weighing 

 88 grams, then the volume of the ice, the salt being inert, is 96 c.c. 

 at 0° ; and when the salt is active, the maximum volume is at the 

 cryohjdric temperature, so that from - 21°* 72, the apparent volume 

 U diminishes as the temperature rises. Therefore for blocks of 

 ice which contain, per 100 parts by weig-ht of ice, less than 

 29*97, and more than 1*7164 parts of NaCl, the coefficient 

 of apparent expansion is negative at all temperatures above 

 2f • 72. 



In Fig. 2 we have curves D and D a, and E and E a. The 

 same constant quantity of chloride of sodium, 1*5105 gram, is dif- 

 fused, in the case of D, in 1 cubic metre, and, in that of E, in 10 

 cubic metres of ice. When melted these blocks of ice would 

 furnish waters containing chlorine in the proportion of 1 gram to 

 1 ton of water in D and to 10 tons of water in E. The critical 

 temperature at which the coefficient of expansion changes sign is 



- 0" * 2275 in D and - 0° • 0725 in E. 



In Table III. we have the upper critical temperature (r) at which 

 the coefficient of apparent dilatation changes sign for blocks of ice 

 having volumes ranging from 100 cubic centimetres to 100 cubic 

 metres, each containing 1*5105 gram NaCl. Under V^ we have 

 the initial volume of the block of ice supposed pure and solid at 0°C., 

 and under v the volume of ice which can be melted under the 

 inducing influence of 1*5105 oram of chloride of sodium at the 



