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diffusive power. No wonder, then, that disinfection is uncertain unless the initial temperature
be raised to a point which injures the fabrics most exposed to its influence.
Contrast this with the action ot Lyons' Patent Disinfecting Chamber. Suppose its
contents to be one hundred cubic feet, and that it be charged with bedding, &c., the doors
secured, and the steam admitted. The contained air, subject to a superior pressure, is
compressed to one-half its volume, less the distension due to heat, so that there remain
50 cubic feet of compressed air, plus 50 cubic feet of steam commingled. The steam
coming in contact with the objects which possess a temperature much below itself,
instantly condenses upon them, parting with its latent heat, and this process is continued
until all the objects accessible to any portion of steam are damped, and raised to a temperature
due to the tension of the steam, viz., at 20 lbs., 2600 F. By the law of diffusion
the steam commingles with the air, and the penetration is complete. If, instead of
admitting steam, heated air had been employed, the effect would have been different in
four respeots.
First.—Moisture would have been absent.
Second. There being no latent heat, to dispose of, the temperature could only have
been raised to a mean between 60 and 260°, says to 160°.
Third.—There could be little diffusion, and
Fourth.—The penetration would be 6mall, for the air when introduced—say, between
two fibres of wool—would give up its heat to them, and to the air about them which it
had compressed, and would there remain; whereas, the steam would give up its latent
heat by condensation, and make room for more live steam behind it. Hence Lyon's
patent process is extremely rapid, for the heat penetrates completely in a few moments.
Now, consider what happens when the pressure is withdrawn. All the objects are heated
to 260°, and are all moist; in other words, are all associated with water raised to 260°
and kept from evaporating by pressure. When the pressure is removed, the water, no
longer restrained, evaporates, and the objects remain in an almost dry condition. Mr.
Lyon, who has made very careful experiments, asserts that insect life is destroyed.
The eggs of lice are subject to a much more severe treatment in the Lyon's Patent
Disinfector than in simple boiling water. A human being may bear a hot bath of 105°,
but he would die instantly if the temperature were raised 50°, or anything approaching
it. These eggs, then, are not subject to 212°, but to 260°, and besides this to a pressure
which is straining the walls of the egg. A gentleman who has studied this subject has a
very interesting theory about these eggs: he considers their elliptical form may probably
enable them to resist the collapsing pressure; but when they have been heated to 260°,
the sudden removal of the 20 lbs. pressure will probably cause the eggs to burst from
the expansion of the vapour generated within them.
The apparatus is constructed of the best materials, and of the form most suitable for
sustaining the required pressure. The articles to be disinfeeted are introduced into the
chamber from one end, and in less than one hour's time are ready for removal at the
other. The Disinfector is arranged with its ingress and egress ends opening into different
apartments, between which there is no communication, save through the Machine itself,
in order to prevent all possibility of contact between infected and disinfected articles, and
the latter should not be distributed in the same vehicles, or by the same men that collect
the former.
Results obtained in Germany by Dr. Koch with super-heated steam,
compared with the effect of hot air:—
Temperature.
Length of
Experiment.
Results.
Action of Hot Air
266° F. to 284° F
4 hours
Articles not fully
disinfected.
,, Steam
194° F. to 221° F
3 hours
Articles entirely
disinfected.
The experiments were made with a bundle of canvas in which was
placed ordinary garden mould; this was entirely sterilized by steam,
but not much affected by the hot air.