ARÆOMETER

ARÆOMETER, an inſtrument to meaſure the density or gravity of fluids.

The areometer, or waterpoſe, is uſually made of glaſs; conſiſting of a round hollow ball, which terminates in a long ſlender neck hermetically ſealed at top: there being firſt as much running mercury put into it as will ſerve to balance or keep it ſwimming in an erect poſition.

The item is divided into degrees (as repreſented Plate XXXVI. fig. 23.); and by the depth of its deſcent into any liquor, the lightneſs of that liquor is concluded: for that fluid in which it ſinks leaſt muſt be heavielt; and that in which it ſinks loweſt lighteſt.

Mr Homberg has invented a new areometer, deſcribed in Phil. Tranſact. N^o 262, thus: A is a glaſs bottle or matraſ, with ſo ſlender a neck that a drop of water takes up in it above five or ſix lines, or half of an inch. Near that neck is a ſmall capillary tube D, about ſix inches long, and parallel to the neck.— To fill the veſſel, the liquor is poured in at the mouth B (which is widened to receive a tunnel), till it run out at D, that is, till it riſe in the neck to the mark C, by which means you have always the ſame bulk or quantity of liquor; and conſequently, by means of the balance, can eaſily tell, when different liquors fill it, which weighs moſt, or is moſt intenſely heavy.

Some regard, however, is to be had in theſe trials to the ſeaſon of the year, and degree of heat and cold in the weather; becauſe ſome liquors rarely with heat and condeſe with cold more than others, and accordingly take up more or leſs room.

By means of this inſtrument, the ingenious author has made a table to ſhow the different weights of the ſame bulk of the moſt conſiderable chemical liquors both in ſummer and winter, as follows:

Weighted in ſummer. In winter. Areometer

The inſtrument itſelf weighed, when empty, one drachm twenty-eight grains. See HYDROMETER.