| 释义 |
hydrometer|haɪˈdrɒmɪtə(r)|
[mod. f. Gr. ὑδρο- water + -meter.
F. hydromètre (first recorded 1768) was app. adopted from English, but has commonly the sense ‘rain-gauge’, the hydrometer being called in F. aréomètre, aræometer.]
1. An instrument for determining the specific gravity of liquids, or sometimes (as in Nicholson's Hydrometer) for finding the specific gravity of either liquids or solids.
The common type consists of a graduated stem having a hollow bulb and a weight at its lower end, so as to float with the stem upright in a liquid, the specific gravity of which is indicated by the depth to which the stem is immersed. Special names are given to it as constructed for particular liquids, as alcoholometer, acidimeter, lactometer, etc.
Nicholson's Hydrometer consists of a brass cylinder having a small pan supported on a stem above the water and another pan dependent below in the water; the specific gravity of a solid body is calculated from the difference of its weights in air and in water, as determined by weighing it in the upper and lower pans respectively.
1675Boyle in Phil. Trans. Abr. II. 214 A New Easy Instrument (a Hydrometer). 1766Smollett Trav. xl. II. 245, I had neither hydrometer nor thermometer to ascertain the weight and warmth of this water. 1819Pantologia s.v., Mr. Nicholson has made an improvement by which the hydrometer is adapted to the general purpose of finding the specific gravity both of solids and fluids. 1860Maury Phys. Geog. Sea v. §285 The hydrometer..shows that the water of the North Atlantic is, parallel for parallel, lighter than water in the Southern Ocean. 1875Knight Dict. Mech. s.v., The most familiar hydrometer, to many, is a hen's egg, used by a farmer's wife to test the strength of lye for making soap.
2. An instrument used to determine the velocity or force of a current; a current-gauge.
1727–41Chambers Cycl., Hydrometer, an instrument wherewith to measure the gravity, density, velocity, force, or other properties, of water. 1864Webster, Hydrometer,..called by various specific names, according to its construction or use, as tachometer, rheometer, hydrometric pendulum, Woltmann's mill, etc. |