Mr. F. Guthrie on Salt Solutions and Attached Water. 7 



the brines are supersaturable in regard to ice, so that the tempe- 

 ratures are most exactly determined by two observations. A 

 good deal of ice is allowed to form ; and this is then suffered 

 nearly entirely to disappear; the temperature is observed at 

 which the ice begins to increase in quantity when the brine is 

 again subjected to cold. 



Table VI. 

 Temperatures at which Brines of various strengths give up Ice. 



(1) 



(2) 



(3) 



(4) 



Water, in 



Brine, in 



Per cent, of 



Temperature 

 at which ice 



grams. 



grams. 



NaCl. 



is first formed. 



60 



140 



18-389 



o 



-15-4 



70 



130 



17 075 



-150 



80 



120 



15762 



-12-4 



90 



110 



14'448 



-111 



100 



100 



13 130 



- 94 



110 



90 



11-821 



- 77 



120 



80 



10508 



- 77 



130 



70 



9-194 



- 67 



140 



60 



7-881 



- 5-4 



150 



50 



6 567 



- 41 



160 



40 



5 254 



- 3-4 



180 



20 



2627 



- 21 



185 



15 



1-970 



- 1-5 



190 



10 



1-313 



- 1-9 (?) 



195 



5 



656 



- 1-5 



200 







0000 



00 



Again the brines which contain 10 to 11 per cent, of salt 

 have singular behaviour in regard to the temperature at which 

 they yield ice. These are the very solutions, it will be remem- 

 bered, which behave singularly in respect of their refractive in- 

 dices and also of their boiling-points. On comparing with Table 

 III., this singularity does not manifest itself in regard to the 

 specific gravities. 



§ 11. Effect of cooling saturated Brine. — It is seen from 

 Table VI. that, as far as the strengths of brine there examined 

 extend, the stronger the brine the greater the cold required to 

 separate ice from it. The strongest brine there examined con- 

 tains 18*389 per cent, of NaCl. If saturated brine (containing 

 26*27 per cent, of NaCl) be cooled, quite a different class of phe- 

 nomena ensues. Down to 0° C. no solidification whatever 

 ensues either of ice or of salt. At —7° crystals of the bihydrate 

 are observed to fall (NaCl-f 2H 2 0). These present a beautiful 

 appearance of iridescent scales heavier than the mother-brine. 

 Their composition has been examined by Lowitz, Fuchs, Nolle, 



