6 Mr. F. Guthrie on Salt Solutions and Attached Water. 



§ 9. Another method of attacking the question is offered by 

 the examination of the boiling-points of various brines. Ac- 

 cordingly I took solutions made by mixing saturated brine with 

 water ; and waiting for a day on which the barometer stood 

 nearly at the mean, I determined the boiling-points of the brines. 

 The vessels were tall copper cylinders. In the Table V. the 

 temperature of the steam, as well as that of the brine itself, is 

 given 

 to avoid the error of strengthening the brine 



The boiling was, of course, only continued a short time, 



Table V. 

 Boiling-points of Brines of various strengths in copper cylinder. 



Per cent, of 



Boiling-point 



Boiling-point 



NaCl. 



in liquid. 



in vapour. 



26-27 (sat.) 



108-8 



107 



18-389 



104-7 



104 2 



17075 



104-2 



1031 



15-762 



104 



102-6 



14-448 



103-4 



102-5 



13130 



1030 



102-3 



11-821 



102-6 



11)1-9 



10-508 



102-4 



102 1 



9194 



102-0 



101-7 



7-881 



101 7 



101-3 



6-567 



101-2 



1010 



5-254 



101-0 



1010 



0-00 (dist. water) 



100-4 



1000 



We have here again a singular value about the 10- to 11 -per- 

 cent, solutions. 



§ 10. Freezing -'points of Brines of various strengths. — The 

 molecular separation of water from salt when a brine is boiling- 

 has to some extent a counterpart in the separation of ice from 

 brine when the latter is subjected to cold. If a weak brine 

 such as 9 of water to 1 of saturated brine (that is, 1 of salt to 

 24*2 of water) is subjected to cold, pure ice begins to be formed 

 in this case at — 1 0, 5. The temperature gradually sinks; but, 

 as has been shown, the solid part consists of ice, which may 

 be completely freed from salt by mere pressure. This forma- 

 tion of ice continues, and the temperature sinks until the in- 

 ferior limit attainable by an ice-salt freezing-mixture is reached 

 ( — 22° C). The brine, of course, becomes richer and richer in 

 salt. In other words, brines richer in salt yield up ice at lower 

 temperatures. Thus, in Table VI. The same brines are examined 

 as were examined in the preceding Tables. The various brines 

 were examined in succession, being contained in small beaker- 

 glasses in an ice-salt freezing-mixture. It is noteworthy that all 



