on 
se 
(2) The fractonating, poluate must. ‘be provided with | an 1 ap 
ssteam Pye | 2) Gamer 
\ 
(6) The hearin must have hore 15mm. wide id wind, exactly 
(7) A boiling pressure of less than 5mm. Hg is to be avoided. 
(8) The rapidity of distillation must not exceed { drop per second. 
U. Dithring’). If t, and te be the baiting Bpae of a Lbetanee at pressures pL anc l po | 
respectively; and if 7, and 7, the boiling points of a second substance at the sa n 
pressure, than, sdstatanl re ot to Dihring:— oo 7 eee ies one: 
fy : Ee 
Ce = constant. ‘ 
The author has now found that this formula is strictly valid when one. ‘only. takes 
into account the pure distillation process; 7.e., the splitting-off of monomolecules from 
the liquid complex, without the occurrence of polymerisation in vapour and liquid. 
In other words, the formula of Dihring is a similar limiting law to the volume la\ 
of Mariotte- -Gay-Lussac, and of similar fundamental significance. __ eit: 
In ‘its numerical evaluation, this law experiences limitations by the. mentioned 
appearance of polymerisation of the vapour; but-the conditions of the fluid complex 
also influence the vapour formation and therewith the unlimited validity of Diihring’s S 
law. It is further seen that no simple formula can be found cape of reprodu rs 
the character of a given vapour’ pressure curve throughout its whole course. Indeed 
continually unsuccessful attempts are made to this end‘); but certain factors combir ei 
and also partly influence each other — at least at higher pressures and temperatures 
so that the expression of the phenomena by means of a formula is impossible. Only 
that part of the curve free from dissociation follows the eS dav of ee ee 
there are two chief types of vaporisation. Water represents one ype t 
other. Very similar to the water curve are: — oxygen, nitrous oxide, phosphine. 
chloride, COs, cyanogen, and of organic compounds:— the acids, the fatty 
PR and the unsaturated fatty compounds with vie adel C9 
validity of the Revise vauee rule). 
i 
1) Zeitschr. f: physik. Chem. 95. een 154, — .*) Wied. Annalen 11 (1880), 168, — 
‘G 
example, P. B. Williamson, Chemical and apt pllaenct eta ee SPD tod ne 
Chem. 1 (1887), 289. — a, ik 
