On Ice and Brines 



composition on cooling, the brine liquefies more and more ice 

 at progressively rising temperatures, until, as before, when the 

 temperature of the mass has risen to o 0> i C, it consists of 

 999,000 parts of ice and 1000 parts of liquid water, containing 

 i part of chlorine. The remainder of the ice will melt at a 

 temperature gradually rising from o'i to o C. 



The consideration of this example furnishes an easy 

 explanation of the anomalous behaviour of ice formed from 

 anything but the very purest distilled water, in the neigh- 

 bourhood of its melting-point. This subject has been studied 

 with great care and thoroughness by Pettersson. The apparent 

 expansion of all but the very purest ice, when cooled below 

 o C., is ascribed by him in part to solid saline contents of the 

 ice which exercise a disturbing and unexplained influence on 

 its physical properties. Viewed in the light of the fact that 

 the presence of even the smallest quantity of saline matter in 

 solution prevents the formation of ice at o C., and promotes 

 its liquefaction at temperatures below o C., we see that this 

 apparent expansion of the ice on cooling is probably due to 

 the fact that we are dealing, not with homogeneous solid ice, 

 but with a mixture of ice and saline solution. As the tem- 

 perature falls this solution deposits more and more ice, and 

 its volume increases. But the increase of volume is due to 

 the formation of ice out of water, and not to the expansion of 

 a crystalline solid already formed. 



TABLE IX. Water containing 7 parts Cl in 1,000,000. 



10-2 



