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Saccharometer
The Hydrometer.
EVERY one is aware that the spirituous liquors known under the name of brandy, rum, etc., are composed of water and pure or absolute alcohol in various proportions. The commercial value of any liquor is therefore in a direct ratio with the amount of alcohol it contains. To ascer tain this is of the highest importance both to the manufacturer and liquor merchant. The per centage of absolute alcohol in any spirituous liquid may be given either by volume or weight, but as liquors are sold by measure, not weight, it is generally preferred to know the per centage by volume. The per cent of weight remains the same in all temperatures, but the per cent by volume varies with the temperature or heat of the liquid. Many instruments have been introduced to determine the quantity of absolute alcohol contained in any spirituous liquors, and these are known as hydrometers, or alcoholometers. Hydrometers made by different inventors have come into use in different countries: thus the hydrometer made by Tralles has been adopted by the governments of the United States and Prussia; that made by Gay Lussac has been legally sanc tioned in France and Sweden, while that invented by Sikes has been approved and made the Excise standard in Great Britain. Mr. Tralles' hydrometer is the in 'rr- (35) ment used by our government to ascertain the strength of imported liquors, and is made of glass. Mr. Tralles has adopted as the standard of comparison pure or absolute alcohol in volume at the temperature of 60° Fah., the strength of which he expresses by a scale divided into 100 degrees or parts, each of which represents 100 part of alcohol. When floated in any spirituous liquor at a temperature of 60° Fah., it immediately indicates the strength. For instance, if in a brandy at that temperature it sinks to 65, it shows that 65 parts of the liquor is absolute alcohol, and 35 parts water: should it sink to 90, it indicates that the liquor is 90 parts or per cent strong, and so on.
An increase of heat causes liquids to expand in volume, and a decrease produces contraction, therefore spirits over the normal temperature of 60° Fah. appear stronger than they really are, and below 60° they are really stronger than they appear to be.* It is therefore evident that the degrees of per centage of this hydrometer, are only correct when the spirit under trial has the normal tempera- * We must always bear in mind one important rule with the hydrometer. It measures, or rather weighs, the densities of fluids, and those fluids are more or less dense as they are colder or warmer. The established standard of temperature from which all calculations are made with the hydrometer is 60°. Ten degrees of heat is about equal to four degrees of density; that is, in alcohol and water-half and half-the hydrometer will stand at 50°, provided the fluid is not more than 60° by the thermometer. Heat the liquid to 70°, and the hydrometer sinks to 54°; cool it to 50° (therm.) and the hydrometer stands at 46°, and so on. And it must be remembered that the stronger the liquid is to the taste, and also in its intoxicating effects, the lighter it is also-the more rarefied; and hence the instrument will almost swim in the punch of a clergyman, and find deep sea-soundings in the punch mixed by a jolly sea-dog who believes only in the three L's, that is, in the log, the lead, and the longitude. -CoZZENS. ture of 60° Fah. When the temperature varies from 60°, the per centage can only be ascertained by a long and tedious calculation. To avoid this Mr. Tralles has constructed a simple table by which the real per centage of alcohol is found in liquids of different temperatures from the results exhibited by the instrument. This we herewith give and will designate it as Table I. The horizontal line at the top shows the various temperatures given by the thermometer; the column of figures under 60° shows the true per centage of strength at the normal or standard temperature of 60°; the figures under the other degrees of temperature show the observed or apparent degrees of strength as indicated by the hydrometers. As an example of the simple manner by which this table may be used, we will suppose that the temperature of the spirits to be tested is at 75°, Fah., and that the hydrometer sinks to 53° on the scale, this would be the observed or apparent degree or per centage of strength. Now to find the real per centage of strength at 60°, we turn to Table I., and find the upright or vertical column of figures headed 75°, we then run down the figures until we arrive at 53.0; having ascertained this, we then trace the horizontal line to the left until we find the column headed 60°, and at the point when the horizontal line running from 53.0 meets the vertical column headed 60°, will be found the number 50. We thus ascertain that a spirit at 75° having an observed strength of 53 has only a real per centage of 50 at the normal or established temperature of 60°.
Suppose that another sample of brandy, instead of being at 75° is at 50°, and the instrument still sinks to 53. In the same way we select the column headed 50°, and run down the figures until we find 53.0 then by tracing the horizontal line running to the right until we arrive at the column headed 60°, we find the number 55, which is the true per centage of the brandy at 60° Fah.
Again, if an alcoholic liquid at a temperature of 30° be found to contain 23.5 per cent, by volume, by reference to the table 30 will be found to express its actual strength at 60° Fah.
We might multiply examples, but the above are sufficient to show the simple manner by which the table may be worked.