EXPERIMENTAL DETERMINATION OF THE FREEZING POINT 201 



point tube F. This tube is surrounded by an air chamber A, which 

 assures a slower and more uniform rate of cooling of the liquid under 

 examination. A stirrer S and thermometer T are introduced into the 

 beaker E which contains the freezing mixture of the desired tempera- 



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Fig. V-8. An assembled freezing-point apparatus. 



ture as predetermined from Table V-9. A metal drain G is used to 

 collect the moisture condensed on E. 



The Beckmann is a mercury-in-glass differential thermometer, with 

 scale readings in degrees Centigrade. It seldom happens that the dis- 

 tribution of mercury between its reservoir and bulb will be such that this 

 thermometer will read exactly 0° C when water freezes. In order to 

 locate this zero point on the Beckmann scale, distilled water is introduced 

 into the freezing tube by way of the side arm D and the zero point is 

 located experimentally. It will be observed that the temperature will 

 fall until ice is formed and then remain constant. This constant- 



