BY MIXTURES OF ELECTROLYTES. BARNES. 145 



This inner freezing-tube was 28 cm. in length and 2.8 cm. in 

 diameter and had its lower end re-entrant. The outer tube was 

 25 cm. in length and 3.15 cm. in diameter. The thickness of the 

 glass being about 1 mm., there was an air space of about 1.5 mm. 

 between the tubes. This space was found to be quite sufficient 

 to prevent the formation of ice on the wall of the tube. The 

 inner tube was supported in the outer by means of two rubber 

 bands, one at the top and the other at the bottom. These bands 

 also prevented the walls from touching one another. The 

 length of the tubes allowed the solution to be well submerged in 

 the protection bath and therefore almost freed it from the 

 influence of the outside temperature. 



In the determination of the freezing-point of a solution these 

 tubes were surrounded by a mixture of salt water and pieces of 

 ice, contained in a vessel of glass 35 cm. high and 11 cm. in 

 diameter (called the protection bath). The cover for this vessel 

 was one taken from the protection bath of a Beckmann apparatus. 

 The glass of this vessel was \ cm. thick and was covered with 

 asbestos paper that the effect of the temperature of the room 

 might be lessened. It was found necessary to keep this bath 

 at a constant temperature within a fiftieth of a degree, if values 

 of the freezing-point agreeing with the mean value to less than 

 a thousandth of a degree were desired. This was obtained by 

 keeping the bath continually stirred. Any change of tempera- 

 ture was quickly recorded by means of a thermometer graduated 

 to a fiftieth of a degree. The temperature of the bath could be 

 raised by the addition of water at the temperature of the room, 

 or lowered by the addition of pieces of ice, snow when obtain- 

 able being preferable. 



The platinum stirrer for the freezing-tube was of the common 

 ring shape, having wound around its ring a thin platinum wire, 

 which would rub against the wall of the tube and thereby 

 prevent the formation of an ice sheath. With constant stirring 

 there was found no tendency for the ice to mass itself together 

 and float to the surface, but it could be seen moving through the 

 whole solution in tiny glistening particles. The stirrer for the 

 PROC. & TRANS. N. S. INST. Sci., VOL X. TRANS. J. 



