On that form of chemical hygrometer in which sulphuric acid has been used as the absorbent : the Johnson memorial prize essay for 1891 / by M.S. Pembrey.

  • Pembrey, M. S. (Marcus Seymour), 1868-1934.
Date:
[1891]
Catalogue details

Licence: Public Domain Mark

Credit: On that form of chemical hygrometer in which sulphuric acid has been used as the absorbent : the Johnson memorial prize essay for 1891 / by M.S. Pembrey. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    To discover these causes Shaw made a few experiments on the condensation of moisture in glass and in india-rubber tubes, and from the results he concludes “ that the increase in weight of the drying tubes after the first, in the Table of results given, was due for the most part to moisture derived from the india-rubber connexions. For the last three observations in the Table, the connexions were made as short as possible, so that the amount of india-rubber surface exposed to the dry air might be small. With the apparatus in that form the drying tubes gained very much less in weight than before, and we may give the results obtained from these three observations as instances of the accuracy which may be expected by the method.” It is probable, however, that Shaw’s absolute weighing is the chief cause of these differences of weight, for it is to be noted that in some cases the tube lost in weight, and that even in the last three experiments the variations are about 16 decimilli- grammes. I think that the following objections may be fairly urged against Shaw’s chemical hygrometer; that, notwithstanding the complication of the apparatus, it does not give such accurate results as Regnault’s simple U-tubes, when the system of comparative weighing is employed; that the mercury joints render the apparatus unfit for travelling and may introduce errors of weighing; that the rate of aspiration, 8 litres per hour, is extremely slow, and makes a determination very tedious. In 1889 an improved method of determining moisture in air was worked out by Dr. Haldane and the writer of this paper. The investigation was suggested by Dr. Haldane, to whom the credit of the method is chiefly due, and arose out of some experiments with a new form of respiration apparatus introduced by him. In order to fully explain the method and to show how we came to adopt the precaution of comparative weighing—a precaution observed, unknown to us, twenty years before by Regnault—I shall take the liberty of inserting here a portion of the original paper ^ “An Improved Method of Determining Moisture and Carbonic Acid in Air.” By J. S, Haldane and M. S. Pembrey. Phil, il/r/f/., April 1890,