and well suited for obtaining alcohol for the preparation of varnishes. Smugglers, who bring spirits into France in bladders hid about their persons, have long known, that although the liquor decreased in bulk, yet it increased in strength; hence the people preferred the article conveyed clandestinely. Professor Graham has ingeniously proposed to concentrate alcohol as follows: "A large shallow basin is covered, to a small depth, with recently burnt quicklime, in coarse powder, and a smaller basin, containing three or four ounces of commercial alcohol, is made to rest upon the lime; the whole is placed under the low receiver of an air-pump, and the exhaustion continued till the alcohol evinces signs of ebullition. Of the mingled vapours of alcohol and water which now fill the receiver, the quicklime is capable of uniting with the aqueous only, which is therefore rapidly withdrawn, while the alcohol vapour is unaffected; and as water cannot remain in the alcohol as long as the superincumbent atmosphere is devoid of moisture, more aqueous vapour rises, which is likewise abstracted by the lime, and thus the process goes on till the whole of the water in the alcohol is removed. Several days are always required for this purpose.' Properties of Alcohol. Absolute. In the state of purity, alcohol is a colourless liquid, highly inflammable, burning with a pale blue flame, very volatile, and having a density of 0.792 at 15.5° C. (60° F.) (Drinkwater.) It boils at 78.4° C. (173° F.) It has never yet been solidified, and the density of its vapour is 1.6133. Anhydrous alcohol is composed by weight of 52 18 carbon, 13:04 hydrogen, and 34.78 of oxygen. It has for its symbol C4 H6 O2 = C1 H3 O + HO, or hydrated oxide of ethyle. It has a powerful affinity for water, removing the water from moist substances with which it is brought in contact. In consequence of this property, it attracts water from the air, and rapidly becomes weaker, unless kept in very wellstopped vessels. In virtue of its attraction for water, alcohol is very valuable for the preservation of organic substances, and especially of anatomical preparations, in consequence of its causing the coagulation of albuminous substances; and for the same reason it causes death when injected into the veins. When mixed with water a considerable amount of heat is evolved, and a remarkable contraction of volume is observed. These effects being greatest with 54 per cent. of alcohol and 46 of water, and thence decreasing with a greater proportion of water. For alcohol which contains 90 per cent. of water, this condensation amounts to 1.94 per cent. of the volume; for 80 per cent., 2.87; for 70 per cent., 344; for 60 per cent., 3.73; for 40 per cent., 344; for 30 per cent., 2.72; for 20 per cent., 1.72; for 10 per cent., 0·72. Alcohol is prepared absolute for certain purposes, but the mixtures of alcohol and water commonly met with in commerce are of an inferior strength. Those commonly sold are "Rectified Spirit," and "Proof Spirit." "Proof Spirit" is defined by Act of Parliament, 58 Geo. III. c. 28, to be "such as shall, at the temperature of fifty-one degrees of Fahrenheit's thermometer, weigh exactly twelve-thirteenth parts of an equal measure of distilled water." very careful experiment, Mr. Drinkwater has determined that this proof spirit has And by the following composition: Spirit which is weaker is called "under proof;" and that stronger, "above proof." The origin of these terms is as follows:- Formerly a very rude mode of ascertaining the strength of spirits was practised, called the proof; the spirit was poured upon gunpowder and inflamed. If, at the end of the combustion, the gunpowder took fire, the spirit was said to be above or over proof. water, the powder was rendered so moist that it did not take fire: in which case the But if the spirit contained much spirit was said to be under or below proof. Rectified spirit contains from 54 to 64 per cent. of absolute alcohol; and its specific gravity is fixed by the London and Edinburgh Colleges of Physicians at 0.838, whilst the Dublin College fixes it at 0.840. In commerce the strength of mixtures of alcohol and water are stated at so many degrees, according to Sykes's hydrometer, above or below proof. This instrument will be explained under the head of ALCOHOLOMETRY, As will have been understood by the preceding remarks, the specific gravity or density of mixtures of alcohol and water rises with the diminution of the quantity of alcohol present; or, in other words, with the amount of water. And since the strength of spirits is determined by ascertaining their density, it becomes highly im. portant to determine the precise ratio of this increase. This increase in density with the amount of water, or diminution with the quantity of alcohol, is, however, not directly proportional, in consequence of the contraction of volume which mixtures of alcohol and water suffer. It therefore became necessary to determine the density of mixtures of known composition, prepared artificially. This has been done recently with great care by Mr. Drink water *; and the following Table by him is recommended as one of the most accurate. Table of the Quantity of Alcohol, BY WEIGHT, contained in Mixtures of Alcohol and Water of the following Specific Gravities: The preceding Table, though very accurate so far as it goes, is not sufficiently extensive for practical purposes, only going, in fact, from 6 to 10 per cent. of alcohol; the Table of Tralle's (page 49) extends to 50 per cent. of absolute alcohol. Moreover, Drinkwater's Table has the (practical) disadvantage (though scientifically more correct and useful) of stating the per-centage by weight; whereas in Tralle's Table it is given by volume. And since liquors are vended by measure, and not by weight, the centesimal amount by volume is usually preferred. But as the bulk of Memoirs of the Chemical Society, vol. iii. p. 454. liquids generally, and particularly that of alcohol, is increased by heat, it is necessary that the statement of the density in a certain volume should have reference to some normal temperature. In the construction of Tralle's Table the temperature of the liquids was 60° F.; and of course, in using it, it is necessary that the density should be observed at that temperature. In order to convert the statement of the composition by volume into the content by weight, it is only necessary to multiply the per-centage of alcohol by volume by the specific gravity of absolute alcohol, and then divide by the specific gravity of the liquid. It has been thought desirable to retain the following remarks by Dr. Ure, and to give Mr. Gilpin's tables in addition to the others. The importance of extreme accuracy in determining the density of alcoholic mixtures in the United Kingdom, on account of the great revenue derived from them to the State, and their consequent high price in commerce, induced the Lords of the Treasury a few years ago to request the Royal Society to examine the construction and mode of applying the instrument now in use for ascertaining and charging the duty on spirits. This instrument, which is known and described in the law as Sikes's hydrometer, possesses, in many respects, decided advantages over those formerly in The committee of the Royal Society state, that a definite mixture of alcohol and water is as invariable in its value as absolute alcohol can be; and can be more readily, and with equal accuracy, indentified by that only quality or condition to which recourse can be had in practice, namely, specific gravity. The committee further proposed, that the standard spirit be that which, consisting of alcohol and water alone, shall have a specific gravity of 0.92 at the temperature of 62° F., water being unity at the same temperature; or, in other words, that it shall at 62° weigh ths or ths of an equal bulk of water at the same temperature. use. This standard is rather stronger than the old proof, which was 13ths or 0.923; or in the proportion of nearly 11 gallon of the present proof spirit per cent. The proposed standard will contain nearly one-half by weight of absolute alcohol. The hydrometer ought to be so graduated as to give the indication of strength; not upon an arbitrary scale, but in terms of specific gravity at the temperature of 62°. The committee recommend the construction of an equation table, which shall indicate the same strength of spirit at every temperature. Thus in standard spirit at 62° the hydrometer would indicate 920, which in this table would give proof spirit. If that same spirit were cooled to 40°, the hydrometer would indicate some higher number; but which, being combined in the table with the temperature as indicated by the thermometer, should still give proof or standard spirit as the result. It is considered advisable, in this and the other tables, not to express the quality of the spirit by any number over or under proof, but to indicate at once the number of gallons of standard spirit contained in, or equivalent to, 100 gallons of the spirit under examination. Thus, instead of saying 23 over proof, it is proposed to insert 123; and in place of 35'4 under proof, to insert its difference to 100, or 64.6. It has been considered expedient to recommend a second table to be constructed, so as to show the bulk of spirit of any strength at any temperature, relative to a standard bulk of 100 gallons at 62°. In this table, a spirit which had diminished in volume, at any given temperature, 0·7 per cent, for example, would be expressed by 993; and a spirit which had increased at any given temperature 0.7 per cent., by 100.7. When a sample of spirit, therefore, has been examined by the hydrometer and thermometer, these tables will give first the proportion of standard spirit at the observed temperature, and next the change of bulk of such spirit from what it would be at the standard temperature. Thus, at the temperature of 51°, and with an indication (specific gravity) of 8240, 100 gallons of the spirit under examintion would be shown by the first table to be equal to 164.8 gallons of standard spirit of that temperature; and by the second table it would appear that 99.3 gallons of the same spirit would become 100 at 62°, or in reality contain the 164.8 gallons of spirit in that state only in which it is to be taxed. But as it is considered that neither of these tables can alone be used for charging the duty (for neither can express the actual quantity of spirit of a specific gravity of 0.92 at 62° in 100 gallons of stronger or weaker spirit at temperatures above or below 62°), it is considered essential to have a third table, combining the two former, and expressing this relation directly, so that upon mere inspection it shall indicate the proportion of standard spirit in 100 gallons of that under examination in its then present state. In this table the quantities should be set down in the actual number of gallons of standard spirit at 62°, equivalent to 100 of the spirit under examination, and the column of quantities may be expressed by the term value, as it in reality expresses the proportion of the only valuable substance present. The following specimen Table has been given by the committee: The mixture of alcohol and water, taken as spirit in Mr. Gilpin's tables, is that of which the specific gravity is 0.825 at 60° F., water being unity at the same temperature. The specific gravity of water at 60° being 1000, at 62° it is 99,981. Hence, in order to compare the specific gravities given by Mr. Gilpin with those which would result when the specific gravity of water at 62° is taken at unity, all the former numbers must be divided by 99,981. Table of the Specific Gravities of different Mixtures, BY WEIGHT, of Alcohol and Water, at different Temperatures; constructed by Mr. Gilpin, for the use of the British Revenue on Spirits. 100 100 100 100 Pure Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 5 10 15 20 30 35 40 Water. Water. Water. Water. Water. Water. Water. Water. Water. Water. 100 100 100 100 100 100 25 45 50 Drg. 30 0-83896 0-84995 0-85957 0-86825 0-87585 0-88282 0-88921 35 -83672 40 45 60 65 70 75 80 85 90 95 100 0-89511 0-90054 0.90558 0-91023 -84769 ⚫85729 •86587 .87357 ⚫88059 .88701 *89294 *89839 *90345 •90811 *$3445 *84539 ⚫85607 ⚫86361 .87184 ⚫87838 •88481 ⚫89073 .89617 *90127 90596 832-4 .84310 85277 ⚫86131 •86905 ⚫87613 .88255 *88849 *89396 ⚫89909 *90380 50 82977 **4076 *85042 .85902 ⚫86676 ⚫87984 •88030 ⚫88626 -89174 .89684 •90160 55 -82736 .83834 *84802 *85664 ⚫86441 -87150 *87796 ⚫88393 .88945 .89458 *89933 -82500 ⚫83599 *84563 ⚫85430 *86208 ⚫86918 *87569 .88169 .88720 -89232 -89707 •82262 .83362 *84334 85193 ⚫85976 ⚫86686 ⚫87337 87938 .88490 .89006 89479 -82023 -83124 -84092 .84951 *85736 -86451 .87105 *87705 -88254 ⚫88773 -89252 -81780 -82878 •83851 ⚫84710 **5496 -86212 *86564 ⚫87466 .88018 .88538 89018 -81530 *82631 *83603 .84467 -85248 *85966 *86622 87228 *87776 N8301 -8-781 81291 -82396 ⚫83371 -84243 *85036 ⚫85757 •86411 •87021 ⚫87590 88120 81044 •82150 ⚫83126 *84001 ⚫84797 .85518 86172 *86787 •87360 *87889 *80794 •81900 *82877 *83753 *84550 -85272 ⚫85928 *86542 *87114 ⚫87654 *8*146 *80548 -81657 ⚫82639 *83513 .84038 ⚫85031 .85688 86302 *86879 -87421 *87915 Temperature, Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol 70 75 Water. Water. Water, Water. Water. Water. Water. Water. Water. Water. Deg. 30 35 40 45 50 55 90 95 100 091449 091847 0-92217 0-92563 0.92889 0-93191 0-93474 0-93741 0-93991 0-94222 By specific gravity. Table of the Specific Gravities of different Mixtures, &c. (continued.) Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Water. Water. Water. Water. Water. Water. Water. Water. Water. Water. 0-94447 0-94675 0-94920 0.95173 0.95429 | 0-956810-95944 0.96209 0 96170 *94249 -94484 *94734 *94988 95246 •95502 95772 *96048 *96315 •94058 91295 94547 •94802 *95060 95328 *95602 *93860 94096 94318 94605 *94871 •95143 •95423 93658 *93897 *94149 -94414 •94683 *94958 $95243 93452 *93696 -93948 94213 .94486 *94767 93247 93493 *93749 -91018 *94296 ⚫94579 •93040 -93285 93516 ⚫93822 •94099 .94388 0-96719 96579 Temperature, Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Alcohol Water. Water. Water. Water. Water. Water. Water. Water. Water. 0-97860 0-981080-98412 0.98804 0-99334 97801 •98076 •98397 •98804 *99344 *97220 .97472 *99284 *99244 99194 99134 99066 Experiments were made, by direction of the committee, to verify Gilpin's tables, The following Table is given by Mr. Lubbock, for converting the apparent specific 82 00083 00078 00065 00052 00039 00025 00012 67° 720 770 800 |