6BCTION 111., 1<J(»4 [ 33 ] Trans. R. S. C. 



V. — The Growth of the Ice Crystal in the Bunsen Ice Calorimeter. 

 By H. T. Barnes, D. Sc, Assistant Prcfessor of Physics, 



AND 



A. S. B. Lucas, B. Sc, Demonstrator of Physics, McGill University. 



(Read June 23, 1904.) 



Various attempts have been made to obviate the slow change in 

 reading that occurs when using the Bunsen ice oalorimeter for accurate 

 work. Under ordinary conditions this change is an increase showing 

 that the volume of the ice is increasing. C. V. Boys, in carefully study- 

 ing the Bunsen ice calorimeter, attributed this increase to the fact that 

 the ice mixture in which the calorimeter was immersed was slightly 

 below the freezing point of the water in the calorimeter. This lower 

 Temperature, he said, was due to the minute quantity ".f saline matter 

 in the ice he used for the mixture. In order to rectify this slow 

 freezing he placed the calorimeter in an air chamber and surrounded 

 the whole with ice. He thus balanced the freezing by a steady melting 

 and was thus able to carry out his measurements. Mond, Ramsay and 

 Shields encountered the same difficulty, and in their investigations where 

 they employed the Bunsen ice calorimeter they follow the method 

 described by Boys. 



The capillary tube used in the apparatus of Boys had a volume 

 of .0001288 c.c. per millimetre, and under the most favourable circum- 

 stances the thread of mercury dropped 1 mm. in three hours, while 

 at other times it fell 4 mm. per hour. 



Mond, Ramsay and Shields worked with a capillary tube having 

 a volume of .0001196 c.c. per millimetre, and the average fall, follow- 

 ing exactly Boys^ arrangemenft, was from 1 to 2 mm. per hour. 



In the experiments carried out by us an attempt was made to 

 obtain steady readings with the ice calorimeter by paying particular 

 attention to the purity of the ice mixtures. If the final conclusion 

 arrived at by Boys is correct and the normal increase in reading, when 

 the calorimeter is directly immersed in the freezing-point mixture, is 

 due to saline matter in the water then by paying particular attention 

 to the purity of the mixture it should be possible to overcome the slow 

 process of freezing in the ice mantle. 



Sec. III., 1904. 3. 



