[maass] freezing point APPARATUS 99 



test tube A has a T tube opposite E, leading outside the freezing bath 

 and closed by a cork stopper B. The experiment is carried out in the 

 ordinary way until it is felt that supercooling has started. Then cork 

 B is removed and a heat extracter H is applied to E. H is a small 

 copper cylinder fastened to the end of a stiff wire and kept immersed 

 up to this time in solid carbon dioxide ( — 78°). The heat capacity 

 of H is small and it is kept in contact with E for only a short time. 

 That suffices, however, to cause a crystal to form at the tip of the 

 platinum wire, with the consequent "freezing" of the solution if 

 supercooling actually has taken place. • 



When the freezing point is determined a second time, it is possible 

 to prevent supercooling of more than one-tenth of one degree and the 

 temperature of the freezing bath throughout need only be half a de- 

 gree lower than the freezing point of the solution. A great advantage 

 is the speed with which freezing points may be determined. The best 

 position for the platinum wire E in the solution is being investigated. 



