AREOMETER
, Aræometrum, an instrument to measure the density or gravity of fluids.
The areometer, or water-poise, is commonly made of glass; consisting of a round hollow ball, which terminates in a long slender neck, hermetically sealed at top; having first as much running mercury put into it, as will serve to balance or keep it swimming in an erect position. The stem, or neck, is divided into degrees or parts which are numbered, to shew, by the depth of its descent into any liquor, the lightness or density of it: for that fluid is heaviest in which it sinks least, and lightest in which it sinks deepest.
Another instrument of this kind is described by Homberg of Paris, in the Memoirs of the Acad. of Sciences for the year 1699; also in the Philos. Trans. N° 262, where a table of numbers is given, expressing the density of various fluids, as determined by this inflrument both in summer and winter. By this table it appears that the density, or specific gravity of quicksilver and distilled water, in the two seasons, were as follow, viz,
| in summer as | 13.61 to 1, |
| in winter as | 13.53 to 1; |
| and the medium of these two is as | 13.57 to 1. |
See also the Philos. Trans. vol. 36, or Abridg. vol. 6, for the description and use of another new areometer.
