424 DETERMINATION OF THE FREEZING-POINT DEPRESSIONS 



of another flask of 200 c. c. capacity. Both flasks were calibrated 

 at 0C. The concentrations, in gramme-equivalents per litre of 

 solutions at 0C., were hence easily calculated. But in some of 

 the cases I was not sure of the dryness of my salt, and hence 

 determined their concentrations gravimetrically by precipitating 

 the KC1 of a known quantity of the solution with Ag NO,. 



Measurement of Freezing-Points. 



The method used in determining the freezing-points was a 

 modification of that used by Loomis.* The principal changes were: 



(1) the stirring was done mechanically and at a constant rate; 



(2) the stirrer was not simply of the ring form but had vanes 

 attached to it; (3) the temperature surrounding the whole 

 apparatus was kept within .5 degree of 0C. The work was 

 clone in a basement room of the college in which there was no 

 source of heat, and experiments were only made when the 

 temperature of the air could be kept at 0C. by raising the 

 windows. 



The freezing-apparatus consisted of three parts as follows : 

 (1) an outer bath containing ice and water ; (2) a bath which 

 stood in this called the protection-bath, and which contained a 

 mixture of salt water and snow, at a temperature of .005 degree 

 centigrade below the freezing-point of the solution, whose 

 freezing-point was being determined ; (3) the freezing-tubes 

 immersed in this, which contained the solution under experiment. 



The freezing-tubes consisted of two glass tubes one inside the 

 other, the outer being about 3.2 cm. in diameter. The 

 space, of about 1 mm., between the two was kept uniform 

 throughout by winding silk thread about the inner one at two 

 distinct places. This air-space, together with one at the bottom 

 of the tubes, caused by the bottom of the inner tube being 

 re-entrant, kept an ice sheath from being formed on the wall of 

 the tube. The two tubes were sealed together at the top, in 

 order to keep moisture from getting in between them, and in 

 order to have their relative positions always the same. These 



*Phys. Review, 1, 199, 1893, and 9, 257, 1899. 



