Of The Areometer Or Proof Bottle

This instrument is indispensable to the distiller: it ascertains the

value of his spirits, since it shows the result of their different

degrees of concentration. I will give the theory of this useful

instrument, as it may be acceptable to those who do not know it.

Bodies sink in fluids, in a compound ratio to the volume and the

density of those fluids, which they displace. It is from that law of

nature, t
at a ship sinks 20 feet in fresh water, while it sinks only

about 18 feet in sea water, which has more density on account of the

salt dissolved therein.

The reverse of this effect takes place in fluids lighter than water, as

bodies floating in them sink the more, as the liquor has less density.

Upon those principles are made two kinds of areometers--one for fluids

denser than water; the other for those that are lighter: the first are

called salt proof; the second spirit proof. Distilled water is the

basis of those two scales: it is at the top for the salt proof, and at

the bottom for the spirit proof; because the first is ascending, and

the other descending; but by a useless singularity, the distilled water

has been graduated at 10 deg. for the spirit proof bottle, and at 0 for the

salt proof. We shall only dwell upon the first, because it is the only

one interesting to the distiller.

Water being graduated at 10 deg. in the areometer, it results from thence

that the spirit going to 20 deg., is in reality only 10 deg. lighter than water;

and the alcohol gaaduated [TR: graduated] at 35 deg., is only 25 deg. above

distilled water.

The areometer can only be just, when the atmosphere is temperate; that

is, at 55 deg. Fahrenheit, or 10 deg. Reaumur. The variations in cold or heat

influence liquors; they acquire density in the cold, and lose it in the

heat: hence follows that the areometer does not sink enough in the

winter, and sinks too much in the summer.

Naturalists have observed that variation, and regulated it. They have

ascertained that 1 deg. of heat above temperate, according to the scale of

Reaumur, sinks the areometer 1/8 of a degree more; and that 1 deg. less of

heat, had the contrary effect: thus the heat being at 18 deg. of Reaumur,

the spirit marking 21 deg. by the areometer, is really only at 20 deg.. The cold

being at 8 deg. below temperate, the spirit marking only 19 deg. by the

areometer, is in reality at 20 deg.. 2-1/4 of Fahrenheit corresponding to 1 deg.

of Reaumur, occasion in like manner a variation of 1/8 of a degree:

thus, the heat being at 78-1/2 deg., the spirit thus marking 21 deg., is only at

20; and the cold being at 87 deg., the spirit marking only 19 deg. by the

areometer, is in reality at 20 deg..

It is easily conceived, that extreme cold or extreme heat occasion

important variations. For that reason, there are in Europe inspectors,

whose duty it is to weigh spirits, particularly brandy: for that

purpose they make use of the areometer and the thermometer. An

areometer, to be good, must be proved with distilled water, at the

temperature of 55 deg.. Areometers, being made of glass, are brittle, and

must be used with great care. This inconvenience might be remedied, by

making them of silver; I have seen several of this metal. A good

silversmith could easily make them; I invite those artists to attend to

that branch of business; it might become valuable, as the distillers

will be more enlightened.