208 Mr. F. Guthrie on Salt Solutions 



is eliminated, there is a rearrangement of the elements more in- 

 testinal than that effected by the association with water. 



§ 44. Effect of the Temperature of the Ingredients on that of 

 the Freezing-mixture. — An ounce of finely powdered chloride of 

 sodium was cooled in a flask surrounded by a freezing-mixture 

 till its temperature was — 15° C. It was then stirred with four 

 ounces of ice, which had been cooled and had the temperature 

 — 10°. As soon as liquefaction began, the temperature —22° 

 was reached ; and this degree of cold was never surpassed. 



§45. The same degree of cold (—22°) resulted from the 

 mixture of 1 oz. of NaCl at —15° with 4 oz. of ice at 0°, also 

 when 1 oz. of salt at + 12° C. was mixed with 4 oz. of ice at 

 -12° C. 



§ 46. Indeed the margin of temperature may be greatly ex- 

 tended. Thus, 1 oz. of NaCl in powder was heated to incipient 

 redness and thrown upon 5 or 6 oz. of ice at 0° ; after a few 

 minutes constant stirring, the temperature had reached —22°. 



§ 47. 1 oz. of dry anhydrous Na 2 S0 4 was heated nearly to 

 redness, and thrown upon 4 oz. of ice at 0°. In a few minutes 

 the temperature had sunk to —0°'7. Again, an ounce of anhy- 

 drous CuS0 4 was heated to about 600° C.» and thrown upon 

 4 oz. of ice; the temperature at once sank to — 0°*5 (compare 

 §55). 



§ 48. From the above experiments, and from the theoretical 

 considerations touched upon in § 42, 1 conclude that, within very 

 wide limits as to quantity, the temperature of a freezing-mixture 

 may be very independent of the temperature both of the salt 

 and of the ice. 



§ 49. Effect of Crystalline Water in the salt on the Tempera- 

 ture of the Freezing -mixture — From § 26 it appears that crystal- 

 lized sulphate of soda (Na 2 S0 4 + 7H 2 O) gives with ice a tempe- 

 rature of — o, 7. Deprived of water, the anhydrous salt N 2 S0 4 

 gave with ice the temperature also of — o, 7. Sulphate of cop- 

 per in the anhydrous state produced, when mixed with ice, a 

 temperature of — 1°*7, while with the ordinary crystallized 

 hydrate the temperature was —2°. 



§ 50. Having examined six or seven other salts as to the tem- 

 perature of their freezing-mixtures when employed both with and 

 without their crystalline water, I do not scruple to assert that 

 water of crystallization, properly so called, takes no effect upon the 

 temperature of the freezing-mixture ; and I believe the same is 

 true of that water which has been called constitutional. But 

 where a profound rearrangement of the elements of water ensues, 

 the effect may be different, as appears in the next paragraph. 



§ 51. The chloride of aluminium, A1C1 3 , as offered in com- 



