Mr. F. Guthrie on Salt Solutions and Attached Water. 3 



Table I. 



Cold produced on mixing saturated Brine with various propor- 

 tions of Water by weight. Initial temperature 21° C. 



(1) 



(2) 



(3) " 



(4) 



(5) 



Water, in 



Sat. brine, in 



Water, 



NaCl, 



Fall of tempe- 



grams. 



grams. 



per cent. 



per cent. 



rature. 











Cent. 



60 



140 



81-611 



18-389 



0-4 



65 



135 



82 268 



17732 



ti-5 



70 



130 



82-925 



17075 



0-6 



75 



125 



84-081 



15-919 



0-75 



80 



120 



84-238 



15-762 



0-8 



85 



115 



84-895 



15105 



0-85 



90 



110 



85-552 



14-448 



0-9 



95 



105 



86-198 



13 802 



0-85 



100 



100 



86-870 



13130 



0-85 



105 



95 



87-522 



12 478 



0-85 



110 



90 



88-289 



11821 



0-85 



115 



85 



88-835 



11-165 



0-9 



120 



80 



89-492 



10-508 



0-9 



125 



75 



90-149 



9-851 



9 



130 



70 



90-806 



9194 



0-9 



135 



65 



91-463 



8-537 



0*75 



140 



60 



92119 



7-881 



0-65 



145 



55 



92776 



7224 



0-6 



150 



50 



93-433 



6-567 



0-6 



155 



45 



94-089 



5-911 



0-6 



160 



40 



94746 



5-254 



0-5 



The greatest depression of temperature accordingly in the 

 range of ratio between 84 and 90 of water and 16 and 10 of 

 salt, and the greatest depression of temperature to be got by 

 mixing saturated brine with water, is under no circumstance 

 quite 1° C. 



§ 5. If now anhydrous salt on dissolving in water absorbs 

 heat only by reason of its conversion into a liquid, and if no 

 hydrate of salt exists at the ordinary temperature above 0° C, 

 no such absorption of heat as we have seen to occur could ensue 

 on mixing brine and water. Two series of experiments are 

 therefore at once demanded : — the first to see what proportion 

 must exist between anhydrous salt and water to absorb the most 

 heat ; the second to see if at any ratio between salt and water 

 an abnormal change of density takes place. 



§ 6. Cold produced on mixing NaCl with Water. — A quantity 

 of rock-salt having been finely powdered, was passed through 

 muslin so as to be quite mealy. Various quantities of distilled 

 water were weighed into beakers, and various quantities of the 

 rock-salt were thrown in under constant stirring. The abasement 

 of temperature being noted gave the results of Table II. The 

 temperature of the salt was about 2° C. above that of the water. 



B2 



