The Romance of Modern Chemistry
Forfatter: James C. Phillip
År: 1912
Forlag: Seeley, Service & Co. Limited
Sted: London
Sider: 347
UDK: 540 Phi
A Description in non-technical Language of the diverse and wonderful ways in which chemical forces are at work and of their manifold application in modern life.
With 29 illustrations & 15 diagrams.
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FACTS ABOUT SOLUTIONS
The separation of pure water from a salt solution,
however, can be carried out not only by freezing, but
by boiling. The latter process, indeed, is more easily
effected, and gives a more perfect separation; it is,
therefore, used on a large scale for the production of
fresh water from sea water. The whole operation of
heating the sea water and condensing the steam which
comes off is known as distillation, and the plant necessary
for carrying this out is part of the regular equipment
of an ocean liner.
It will be obvious to the reader that one result of
boiling a solution, and thus getting rid of some of the
water, will be to increase the strength of the solution,
provided, of course, that the dissolved substance itself
has no tendency to volatilise. Now, as already stated,
the greater the concentration, the higher is the boiling-
point If, therefore, a thermometer is put in a solution,
say, of sugar, which is boiling in an open vessel, the
readings of the thermometer will get higher and higher.
Any one who has made fondant for confectionery pur-
poses will have observed this. In this operation sugar
and water are mixed in certain proportions in a pan
and heated; the temperature rises rapidly to the point
at which the mixture begins to boil, and then slowly
thereafter as the water is boiled off and the sugar solution
concentrates. The subsequent behaviour of the sugar
solution when cold varies with the extent to which this
concentration has been allowed to proceed ; it depends on
the temperature at which the boiling has been stopped.
In the endeavour to bring home to the reader the
curious properties exhibited by solutions, the writer has
taken sugar or salt as the dissolved substance. These
compounds have the advantage of being perfectly well
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