I02 
It is well known that for this simultaneous distillation of two non- 
P MF 
miscible liquids, the formula — = ^^^^ applies, in which P and P^ 
represent the quantities by weight of the two substances distilling over 
in the unit of time, M and their molecular weights, F and F^ the 
steam - pressure during the distillation. On the strength of this pro- 
position E. Charabot and J. Rocherolles^) have subsequently de- 
termined, experimentally as well as by calculation, what influence 
P 
an alteration in the temperature has on the ratio — » and they found 
that, according to the selection of the liquids distilling simultaneously, 
this value is either larger or smaller than i. When water is distilled 
simultaneously with limonene, geraniol, linalool, citronellol, or methyl 
heptenone, it advances with increasing temperature towards i, whilst 
with pinene, benzene, isopentane, or normal hexane, with increasing 
temperature, it falls towards i. In other words, of the above-named 
substances, such as linalool, etc. when distilled simultaneously with 
water more will pass over at ordinary pressure than at reduced pressure; 
on the other hand, in order to obtain the same result with substances 
such as pinene, etc., it will be necessary to perform the simultaneous 
distillation of one of these bodies with water, at reduced pressure. The 
two last-named chemists have lately 2) applied these conditions to the 
distillation with water vapour which is of such enormous importance 
for the manufacture of essential oils, and they distinguish the follow- 
ing two cases, after tests as described : i . Water vapour passed through 
turpentine oil which in a vessel was kept at a lower temperature than 
the combined boiling point of water and turpentine oil (about 98°). 
Here, while the oil was simultaneously heated to the combined boiling 
temperature of water and turpentine oil, a condensation of steam 
naturally took place, and with it a distillation of two non-miscible liquids. 
This phenomenon was therefore identic with the one mentioned above. 
2. Another result, however, was obtained with the test when the tempe- 
rature of the oil was raised above the common boiling temperature 
of water and oil (i. e. above 100°). Here, of course, no conden- 
sation of steam took place. 
P Mw 
The formula — = is here sufficiently exact; h represents 
the tension of the water vapours (equal to the pressure in the vessel), 
99 the tension of the oil vapour saturated with steam, with regard to 
the temperature of the mixture of the vapours of the two liquids. It 
^) Compt. rend. 135 (1902) 175. 
^) Compt. rend. 138 (1904), 497. 
