232 
SELECTED ARTICLES. 
temperature remained constant as long as there was a sufficient 
quantity of the more volatile liquid to pass over, drop by drop. 
Thus, for example, the temperature, at which newly rectified 
oil of turpentine mixed with water, enters into ebullition, is 
102° C, under the pressure of 749 mm .6, whilst that of the 
vapor is but 94°.5 C. A mixture of carburet of sulphur and 
water boils at 47° C, under the pressure of 752 mm .2; the 
vapor is but 43°.5 C. As long as any carburet of sulphur 
could be perceived, these temperatures were constant, and 
there distilled over carburet of sulphur and water; but when 
the carburet of sulphur could no longer be seen, the tempe- 
rature of the liquid and of the vapor rose, and boiling and 
distillation ceased. 
When a mixture of two liquids boils, the temperature 
should be so high that the vapors of the more volatile liquid 
may be disengaged freely, and have an expansive force equal 
to the pressure operating upon them. It is then necessary 
that the bubbles of the more volatile liquid, as well as that 
which they carry off with them, should have a temperature 
equal to the boiling point of that liquid, otherwise vapor 
would form only at the surface, and there would be no dis- 
engagement of bubbles. If this liquid occupies the inferior 
part, it will be opposed, not only by the pressure of the 
atmosphere, but by that of the super-incumbent liquid; it 
should, therefore, take a higher temperature for boiling than 
under the pressure of the atmosphere. In the case of the 
liquids upon which I operated, and in which the lower place 
was occupied by the more volatile liquid, the boiling point of 
the mixture was very near that at which the more volatile 
liquid should boil under the increased pressure. Whilst the 
vapors passed through the less volatile liquid, the space which 
they occupied acted as empty space, into which the vapors of 
the less volatile liquid entered; then the vapors of the more 
volatile liquid expanded, and took a more feeble tension, as 
the tension which the vapors of the less volatile liquid exer- 
cised were weaker. For the formation of the vapors of the 
less volatile liquid, and for the expansion of the vapors of the 
