On the penetrativeness of fluids / by J.K. Mitchell.

  • Mitchell, John Kearsley, 1793-1858.
Date:
1830
Catalogue details

Licence: Public Domain Mark

Credit: On the penetrativeness of fluids / by J.K. Mitchell. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    In the course of an investigation of mixed gases through capillary open- ings, the following singular observation was made. A sound bladder with stop-cock, was filled about two-thirds with coal gas, and the stop-cock shut; the bladder was passed up in this flaccid state, into a bell-jar receiver, filled with carbonic acid gas over water. The bladder was thus introduced into an atmosphere of carbonic acid gas. In the course of twelve hours, instead of being in the flaccid state, in which it was left, the bladder was found distended to the utmost, and on the very point of bursting, while most of the carbonic acid gas in the receiver had disappeared. The bladder actually burst in the neck, in withdrawing it from under the receiver. It was found to contain thirty-five parts carbonic acid gas by volume in one hundred. The substance of the bladder was quite fresh to the smell, and ap- peared to have undergone no change. The carbonic acid gas remaining with- out in the bell-jar, had acquired a very little coal gas. The conclusion is unavoidable, that the close bladder was inflated by the insinuation of carbonic acid gas from without. In a second experiment, a bladder containing rather less coal gas, and similarly placed in an atmosphere of carbonic acid gas, being fully inflated in fifteen hours, was found to have acquired forty parts in one hundred of this latter gas, a small portion of coal gas left the bladder as before. A close bladder, half-filled with common air, was fully inflated in like man- ner, in the course of twenty-four hours. The entrance of carbonic acid gas into the bladder, depends, therefore, upon no peculiar property of coal gas. The bladder partially filled with coal gas, did not expand at all in the same jar containing common air or water only. M. Dutrochet will probably view, in these experiments, the discover}' of endosmose acting upon aeriform matter, as he observed it to act upon bodies in the liquid state. Unaware of the speculations of that philosopher, at the time the experiments were made, I fabricated the following theory to account for them, to which I am still disposed to adhere, although it does not involve the new power. The jar of carbonic acid gas standing over water, the bladder was moist and we know it to be porous. Between the air in the bladder, and the carbo- nic acid gas without, there existed capillart canals through the substance of the bladder filled with water. The surface of water at the outer extremity of these canals being exposed to carbonic acid gas, a gas soluble in water, would necessarily absorb it. But the gas in solution, when permeating through a canal, it arrived at the surface of the inner extremity, would rise as necessari- ly into the air in the bladder and expand it. Nothing but the presence of car- bonic acid gas within, could prevent the disengagement of that gas. The force by which water is held in minute capillary tubes, might retain that liquid in the pores of the bladder, and enable it to act in the transit of the gas, even after the pressure within the bladder had become considerable. A careful perusal of Mr. Graham's notice, will excite in every one who knows the value of experimental interrogation, an expres- sion of surprise, at the failure, on the part of that intelligent and in- genious chemist to pursue in the only true spirit of science, the