VII. Re-determination of the mass of a cubic inch of distilled water
The evaluation of the mass of a cubic inch of distilled water, as at present accepted, was based on weighings made in 1798 by Sir G. Shuckburgh ('Phil. Trans.,’ 1798, p. 133); and on measurements made in 1821 by Captain Kater (‘ Phil. Trans.,’ 1821, pp. 316 and 326). Subsequent researches however, particularly those in relation to the mass of a cubic decimetre, show that it is desirable to re-determine the mass of the cubic inch of distilled water. The result of Shuckburgh’s experiments was that the cubic inch of distilled water at the temperature of 66° Fahr., the barometer being at 29·74 inches, weighed 252·422 grains, and this value as corrected by Captain Kater, became 252·458 grains at the temperature of 62° Fahr., the barometer being at 30 inches; or in vacuo ( t . = 62° Fahr.) the cubic inch of distilled water wreighed 252·724 grains. This corrected value, 252·458 grains, has been adopted in various legislative enactments;— for instance the Weights and Measures Act, 5 Geo. IV., c. 74, section 5 (1824), declared that “a cubic inch of distilled water, weighed in air by brass weights, at the temperature of sixty-two degrees of Fahrenheit’s thermometer, the barometer being at thirty inches, is equal to two hundred and fifty-two grains and four hundred and fifty-eight thousandth parts of a grain, of which the imperial standard Troy pound contains five thousand seven hundred and sixty.”