BROMINE 33 



The substances whose compressibilities we have determined are 

 bromine, iodine, chloroform, carbon tetrachloride, bromoform, phos- 

 phorus and water, while from the results we may also obtain the value 

 for glass and a qualitative indication of the compressibility of liquid 

 chlorine. In every case the temperature was 20 . Further details 

 are best discussed under the individual experiments. 



Bromine. 



Two samples of bromine were used. The first specimen (used in 

 all but the last series) was prepared by the usual calcic bromide 

 method of Stas. It was subjected to an initial distillation, was dried 

 by means of phosphorus pentoxide, and twice redistilled, but was not 

 wholly free from dissolved air. Sample two (2) was an especially 

 pure specimen which had been prepared by Richards and Merigold ' 

 for their work on the atomic weight of uranium. It was dried over 

 phosphorus pentoxide and redistilled. The air was expelled by boil- 

 ing just before use. 



The equation for the calculation of the compressibility shows that it 

 is necessary to know accurately the specific gravity of the substance 

 under examination. Thorpe 2 found as the specific gravity of bromine 

 at o (water at 4 being the standard) the value 3.1882. Pierre* 

 found, with the same standard and temperature a value, 3.18721. He 

 found also that between 7 C. and 60 C. the expansion formula is 



V= 1 -f .001 038 18 / -f .000001 7114/'+ .000000005447 f. 



The average of the values of these two experimenters, viz., 3.1877, 

 was taken as the density (o/4), and with this as a basis the value at 

 20 C. was obtained by the use of Pierre's formula. The result is 

 3.120 (2o/4), and this value was used in the calculations 

 below. 



There are given below the essential data and results of five series of 

 experiments upon bromine, made with two different portions of ma- 

 terial and two different jackets. 



In series 1, 2, 3 and 4, the weight of bromine was 7.504 grams, 

 corrected to vacuum, and the containing thin bulb weighed w" = 0.72 

 gram. In series 5 the bromine (the second sample, free from dis- 

 solved air) weighed 12.649 grams (in vacuum) and the glass bulb 

 weighed w" = 1.10 grams. 



1 Proc. Am. Acad., 37, 387 (1902). 



*Journ. Chem. Soc, 37, 172 (1880). 



3 Ann. de Chim. et Phys. (3), 20, 45 (1847;. 



