CHEMISTRY. 7 
property of liquids by which ebullition and consequent evaporation take 
place at certain temperatures. The ebullition or boiling of liquids consists 
in the fact that, after they are heated to a certain point, any additional 
increment, instead of being sensible to the thermometer, is expended in a 
combination with individual particles of the liquid. Thus water, when 
heated, gives indication to the thermometer of a rise of temperature up to 
100° C., 800 R., or 212° F. Arrived at this point, the temperature remains 
fixed, provided that no change takes place in the height of the barometer, 
and the additional heat, instead of elevating the temperature, appears to 
combine with the atoms of water, expanding them to such a degree as 
to convert them into vapor or steam. The heat disappearing in this manner 
is said to become latent, as it cannot be indicated by the thermometer. 
although actually existing. For when this vapor or steam is led into cold 
water, its consequent condensation is accompanied by a rise in the tempera- 
ture of the water corresponding to the amount of heat rendered latent. The 
boiling point of liquids, or the limit of the ascent of temperature at which 
ebullition takes place, depends greatiy on the pressure of the atmosphere. 
boiling taking place sooner as the pressure is less. Thus, on the top of 
Mont Blanc, water boils at 187° F. 
The process of distillation is generally employed to separate liquids 
of different boiling points from each other. Thus, in the fabrication of 
whiskey, after the fermentation of the mash, a mixture is produced from which 
the alcohol formed is to be separated, and obtained tolerably free from water. 
Pure anhydrous alcohol boils at 172.4° F., water at 212° F. On bringing the 
mash into a distilling vessel. and regulating the fire so that the temperature 
of the vessel shall not rise to the boiling point of water, the latter cannot 
pass over in any great quantity as vapor, while the spirit evaporates as soon 
as its own proper temperature has been exceeded. By cooling the tube 
terminating the distillatory apparatus, the vapor will be again condensed. 
and a liquid obtained which contains a much larger proportion of alcoho! 
than before. The spirit will not be perfectly pure, inasmuch as some 
watery vapor will pass over; the amount of this will, however, be less as 
the temperature at which the operation is performed is lower. 
It is very evident that we may separate vaporizable liquids from 
substances mixed with them, provided the latter require a higher temperature 
for vaporization than the former. The usual apparatus of distillation on a 
small scale is the retort; for larger operations, the alembic or the still. For 
most distillations of liquids we may use retorts of glass ( pl. 30, figs. 25 and 
26). In fig. 26 the liquid is introduced by means of a tube which is longer 
than the neck of the retort ; in fig. 25 by means of a funnel through the 
head @ in the bulb of the retort, this aperture being closed by a well ground 
stopper. The retort thus arranged is placed in the sand bath furnace 
(fig. 8). The space E forms a sand bath composed of tin: it is exhibited 
more fully in fig.9. On its bottom is placed a thin bed of dry sand, and the 
retort, after being set on this, is surrounded by an additional quantity of 
sand. The bath has a notch cut out of the edge to receive the neck of the 
retort. The vessel or tube applied to the extremity of the neck of the 
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