104 DB. B. D. STEELE, DR. D. McINTOSH AND DR. E. H. ARCHIBALD 



The formation of hydrogen was reduced to a minimum by the device of leaving in 

 the manometer a small quantity of air, which prevented the hydrogen bromide (or 

 iodide) from reaching the surface of the mercury until a considerable time had 

 elapsed. 



-60 



ZOO 



400 600 



FffESSURE //V MILLIMETRES OF AfffiCL/ffY 



Fig. 3. 



The results of the measurements are collected in Table I., which contains the 

 experimental (a) and smoothed (b) values of the vapour-pressure for each of the 

 liquefied gases. 



In the case of hydrogen bromide and iodide the measurements have been continued 

 considerably below the melting-point, and the vapour-pressure curve both for solid 

 and for liquid are given in fig. 3. It will be noticed that the change in curvature at 

 the melting-point is very slight both for hydrogen bromide and for hydrogen iodide. 



The melting- and boiling-points found by us for the pure substances are given in 

 Table II., together with recent measurements by other observers. 



