Health-culture / by Gustav Jaeger ; translated and edited by Lewis R.S. Tomalin.

  • Gustav Jäger
Date:
1902
Catalogue details

Licence: In copyright

Credit: Health-culture / by Gustav Jaeger ; translated and edited by Lewis R.S. Tomalin. Source: Wellcome Collection.

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    off when warmed. If, on the other hand, the bottle in which the air bubbles have appeared be returned to a cool place, in proportion as the temperature of the water falls, the bubbles become smaller and smaller, until at last they quite disappear; the air has re-entered the water. This phenomenon, which is termed by Physicists the absorption of gases by fluids, must, for our purpose, be enlarged on in two directions. The faculty of absorbing air, i.e. gases, under cold, and of giving them out again under warmth, is not peculiar to fluids alone, but is also possessed by solid bodies, especially if the latter are porous. It is known, for instance, that platinum absorbs oxygen, and that ordinary earth is able to condense matters out of the atmosphere into itself, whence the employment of earth for deodorising deposits in latrines. 'I'he power of charcoal to absorb volatile matters and such as are in a state of solution, is equally well known, and use is made of this power, especially for the filtration of drink- ing water, &c. It is also true of these solid bodies, that the lower their temperature the more they absorb, and that, when warmed, they give off a portion of what they have absorbed. But there is another factor in the case of solids which is absent in that of fluids. When a solid has absorbed gases, an additional means to expel a portion of these is by wetting it. I will give two common examples. When an ordinary floor of a room is wetted it gives out a disagreeable odour; similarly, when rain has fallen, the earth gives out an odour. These odours disappear so soon as the bodies are again dry. If we test various kinds of matters—fluids in the first ])lace—we shall find that what they, when in a state of cooling, take up from the air is not always the same ; each species of fluid does not attract the ingredients of the air in an equal degree, but invariably evinces a certain prefer- ence for one or another element. This has long been 2
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