ON THE HALOGEN HYDRIDES AS CONDUCTING SOLVENTS. 



109 



The numbers obtained by the foregoing method have been checked in the case of 

 hydrogen chloride, hydrogen bromide, and hydrogen iodide by distilling each of them 

 into a thick-walled bulb of known volume, and sealing it. After the bulb containing 

 the liquid had been weighed it was cooled, the stem broken, and the empty bulb and 

 stem again weighed. 



The densities so obtained agreed to the 3rd decimal place with those obtained at 

 the same temperature by the first method. 



In the case of phosphine the density was determined by the second method and the 

 temperature coefficient by the first method. 



The results of the measurements are given in Table III., in which D' represents 

 the experimental and D the smoothed value of the density. The density in each case 

 is a linear function of the temperature and is given by the relation 



D T , = D T [l + a(T-T')], 



where T and T' represent the boiling-point and the temperature of observation 

 respectively, both on the absolute scale ; D T and D T , being the corresponding 

 densities. 



The values of the coefficient a for the different substances are contained in the 

 following table : 



TABLE III. Densities. 



