1909-10.] Boiling-Points under Constant Conditions. 435 
(3) That the conditions are definite and easily reproducible with exact- 
ness, and that, in particular, it is impossible for the liquid, the vapour, and 
the thermometer to differ in temperature. The boiling-points ascertained 
are therefore more accurate, and more exactly comparable than are those 
obtained by the usual method. 
(4) That with impure or decomposing liquids a fractional distillation in 
miniature may quickly be carried out and the impureness recognised. 
(5) That when the dissolved or occluded gases or volatile substances 
which are always present can be removed by boiling, the removal may be 
accomplished and a satisfactory boiling-point secured. 
(6) That by taking the boiling-point of a mixture of the two, the 
identity or non-identity of two liquids of almost identical boiling-points 
may often be ascertained without sacrifice of an appreciable amount of 
material. This method will apply, however, only when the two substances 
are of chemically dissimilar natures, and not usually to very similar 
substances.* 
(7) That the method may be adapted to finding boiling-points at normal 
pressure (760 mm.), and under reduced pressure (see next two papers). 
* Young, Stoichiometry (London, 1908), 264. 
(. Issued separately June 16, 1910.) 
