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.

  • Marcus Seymour Pembrey
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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    himself, but he thought that other liquids might be found for floating the bulb. Against the fragility of the instru- ment its inventor protests that it may he made of metal. Snellen^ in 1874 described another form of sulphuric acid hygrometer. It consisted of a U-tube containing pumice soaked in sulphuric acid and with the entrance and exit tubes each bent through two right angles, so that their free extremities, which were enlarged, might dip into vessels of olive oil. The absorption-tube was flxed to one arm of a balance and counterpoised by weights. As in Baumhauer’s hygrometer air was drawn through the ap- paratus by means of glass tubes passing through the oil and opening into the bulbous ends of the entrance and exit tubes. Snellen gives no figure of his hygrometer, nor does he describe any observations to test its accuracy or practical value. A serious objection to this instrument is that variations may arise from changes in the density of the oil. In 1879 an important research on hygrometric methods was undertaken by Shaw at the request of the Meteoro- logical Council, and in 1888 the first part of his valuable report was published in the Philosophical Transactions This observer made a number of experiments on the chemi- cal method, employing drying tubes of a special form (Fig. G) The U-tubes, about 6 inches long and \ inch internal diameter, were fitted with wide glass connexions, one extremity of which was ground into the U-tube, while the other passed over narrow tubes coming through small mercury cups, and thus forming the connexions between the drying tubes and the other parts of the apparatus. These mercury joints Shaw considers superior to india- rubber connexions. The drying tubes were filled either with coarse fragments of pumice saturated with the strongest sulphuric acid or ^ “ Sur un Hygrometre a Balance,” Archives Neeihuulaises des Sciences Exactes et Nedurelies, t. ix. p. 477 (1874). ^ Philoso])hic(d Trcoisaclions, 1888, vol. A, p. 73, See p. 18.