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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    drogen had made its escape. In the next experiment the arrangement of the gases was altered: common air was enclosed in the bottle, and a bell-glass confined around it an atmosphere of hydrogen. As was expected, the hy- drogen entered the bottle rapidly, raised up the tense membrane, formed it into a globe, and finally burst through it, and thus made its escape from the confinement to which it had been spontaneously subjected. The minuteness of the atom of hydrogen might readily enough ac- count for the greater facility with which it penetrated the membrane, but could not be considered a good reason for the energy with which the penetration was accomplished. A gas having a heavy atom was therefore selected for further experiment, and carbonic acid, subjected to the same sort of confinement was found to permeate the membrane with as great power, and very much greater facility. In succession, most of the gases were submitted to the same ordeal, and all oi them found, except nitrogen gas, to exercise the same power, but with very different degress of rapidity. The power was ascer- tained by comparison with common air, and the rate of action both in that mode and by comparison with each other. The depression or elevation of the membranous cover, clearly indicated the escape or entrance of a gas, and when two active gases were placed one on each side of it, its rise or fall expressed the difference of rate, be- cause each was, at the same moment, in the act of permeation, as proved by many examinations of the contents of the bottle and bell- glass. Having once ascertained the rate of action of each gas relative to air, a prediction could be made as to their rate in reference to each other. Hence gases which operated on air with nearly equal ve- locity, affected the horizonlality of the membrane very little when placed on opposite sides of it. Thus carbonic acid and nitrous oxide act with great facility on common air, and in nearly equal degree; and when placed on opposite sides of the membrane, penetrate it ra- pidly, but cause a very slow change in its position. The facts here presented warrant the conclusion, that if two gases, equally pene- trant exactly, could be found, they would under the above described arrangement, mix uniformly, without in the slightest degree altering the state of the membrane.* * Subsequently having1 discovered that defiant gas and arsenuretted hydro- gen, have, with reference to common air, exactly equal rates, they were placed