Cooley's Cyclopaedia of Practical Receipts Volume I Part 21

_Hist., &c._ The great importance of being able accurately to determine the strength of spirits in the United Kingdom, on account of the high duties levied on them, has induced the Government authorities, at various times, to investigate the subject. In 1790, the matter was referred to Sir C. Blagden, then Secretary to the Royal Society, who inst.i.tuted an extensive series of experiments to determine the real specific gravities of different mixtures of alcohol and water. The results of his labours and researches were put forward, with 'Gilpin's Tables,' in 1794, but no practical measures appear to have been taken in consequence. In 1832 a committee of the Royal Society, at the request of the Lords of the Treasury, examined into the accuracy of the Tables, and the construction and application of the instrument (SYKE'S HYDROMETER) now used by the Revenue officers, on which they reported favorably, and declared that they were sufficiently perfect for all practical and scientific purposes. The errors introduced into calculations of the strength of spirits by these tables were found to be quite unimportant in practice, and did not, in any one instance, amount to unity in the fourth place of decimals. This method adapts the specific gravity as the test of the strength of spirits, and is founded on the fact that alcohol is considerably lighter than water, and that (with proper corrections for condensation and temperature) the sp.

gr. regularly increases, or decreases, according to the relative proportions in which the two are mixed.

Several other methods of alcoholometry have been proposed, founded upon--the variations in temperature of the vapour of alcohol of different strengths--the heat involved by its admixture with water--its dilatation by heat--the tension of its vapour--the insolubility of carbonate of potash in alcohol--its volatility, boiling point, &c. &c., the more important and useful of which are noticed further on. The method adopted by the Boards of Inland Revenue and Customs is, however, the one which is almost exclusively employed in trade and commerce in Great Britain, not only on account of its simplicity and correctness, but for the purpose of the results exactly coinciding with the results obtained by the Revenue officers.

METHODS OF ALCOHOLOMETRY.

1. _Methods based_ on the _specific gravity_, or _per-centage strength_, by VOLUME:--

[Ill.u.s.tration]

_a._ With SYKES' HYDROMETER. _Revenue system._ The _engraving_ below represents Sykes' hydrometer, as made by Mr Bate, under the directions of the Commissioners of Inland Revenue and Customs. It consists of a spherical ball or float, with an upper and lower stem, and is made of bra.s.s, which (in the more expensive instruments) is usually coated with gold, to prevent corrosion from damp, and the acidity so generally present in spirituous liquors. The upper stem (A) is about four inches long, and is divided into ten parts, each of which contains five subdivisions. There are nine movable weights of the form _b_, of different sizes, numbered respectively 10, 20, 30, &c., to 90, each of which represents so many of the princ.i.p.al divisions of the stem, as its number indicates. In use, one of these weights is slipped on to the lower stems; and thus, by means of them, the instrument acquires a range of above 500 divisions, or degrees, extending from the Revenue 'standard alcohol' (sp. gr. 825) to water. It is so formed as to give the sp. gr. with almost perfect accuracy, at 62 Fahr. When loaded with the weight 60 it sinks in proof spirit to the line marked (P) on the narrow edge of the stem at 51 Fahr.; and, by further placing the square weight or cap (also supplied with the instr.) on the top of the upper stem, it floats exactly at the same point in distilled water. This weight or cap is found to weigh 4366 grs., which is practically 1-12th of the total observed weight of the instrument, and its poise 60, and hence shows the difference between the gravity of proof spirit and water, as explained hereafter. The whole is fitted up in a neat mahogany case, accompanied with a thermometer, and a book of tables containing corrections for temperature, &c.--_Process._ A gla.s.s tube of the form of fig. _B_ is filled to about the mark (_a_) with the sample for examination; the thermometer is then placed in the liquor, and stirred about for two or three minutes (observing not to breathe upon the gla.s.s, nor hold it in the hand), and the temperature noted. The hydrometer is next immersed in a similar manner, and gently pressed down in the liquor to the 0 on the stem with the finger; it having been previously loaded with any one of the nine weights that will cause it to float with the surface of the spirit at some point on the graduated part of the scale.

The indication at the point cut by the surface of the liquor, as seen from below, added to the number of the weight with which the float is loaded, gives a number which must be sought in the hook of Tables, which is always sold with the instrument. In this book, at the page headed "Temperature as observed by the Thermometer," and against the part of the column appropriated to the given indication (weight), will be found the strength per cent., expressed in degrees over or under proof, by VOLUME, in whole numbers or decimal parts. In reading off the indication, to ensure accuracy, it is necessary to allow for the convexity of the liquor at the part where it immediately rests against the stem.

_Obs._ In an instrument requiring so much care and skill in its manufacture the purchaser should be careful to procure a perfect one. A very slight blow, friction from continual wiping with a rough cloth, and other apparently trivial causes, tend to injure so delicate an instrument.

The shape of the weights occasionally vary; some being intended to be attached to the hydrometer at the bottom of the spindle, and others to rest on its top. The first plan is, perhaps, the best, as it tends to make the instrument float with greater steadiness in the liquor; but, at the same time, it renders its adjustment by the maker a matter of greater difficulty.

In employing this instrument, the Revenue officers are instructed to take the nearest degree above the surface of the mercury, when it stands between any two degrees of the thermometer; and the division on the scale of the hydrometer next below the surface of the liquid, when it cuts the stem between any two lines; thus giving the difference in favour of the trader in both cases.

By means of the _Table_ at page 64 the hydrometer indication, or the degrees over or under proof, of the Revenue system, may be converted into 'real specific gravities,' by mere inspection; and the corresponding 'per-centage richness' in alcohol of any sample may be found, either by WEIGHT or VOLUME.

The specific gravities in this table are such as, on being referred to Gilpin's Tables, will give the expressions of proof strength answering to the whole indications of the Revenue hydrometer. Intermediate values at fifths of indications may be had by taking proportional differences between the nearest tabular numbers. Thus, to find the specific gravity that should stand opposite to Indication 706, we first obtain the difference between the densities standing in a line with Indications 70 and 71 respectively, and then say, as 1 : 06 :: 00192. 00115, and 94135 + 00115 = 94250, the specific gravity required.

_b._ With GLa.s.s ALCOHOLOMETERS. That of Tralles, and most others of a like description (as made in England), gave the per-centage strength, by VOLUME, with tolerable accuracy, at the standard temperature of 60 Fahr.

Gay-Lussac's ALCOoMETRE, which closely resembles that of Tralles, is adjusted for the temperature of 59 Fahr. (15 Cent.). All of these, to give at once accurate results, must, of course, be employed at the 'normal temperature' of the instrument. As, however, in practice, the experiment cannot be conveniently performed at any 'fixed' temperature but only at that of the atmosphere, it is obvious that certain corrections are constantly required in order to obtain results of any value. Perfect accuracy requires that table for every variation of the thermometer, founded on actual experiments, should accompany each instrument; as, without them, tedious and difficult calculations are necessary, which, in the hurry of the cellar and laboratory, or by persons inexpert at figures, are not easily performed. A series of such Tables were prepared by Gay-Lussac, and, with his instrument, are those which are almost exclusively used in France. For rough purposes, in the absence of Tables or nicer calculations, it may be useful to know that, for commercial spirits, at ordinary temperatures, a variation of--

By VOLUME, 5 Fahr. is equal } 100% of Alcohol; } 1794% of Proof to (about) } or (about) } spirit.

1 " " 020% " 0359% "

5 Cent. " 180% " 3229% "

1 " " 036% " 0646% "

By WEIGHT, 5 Fahr. is equal } 080% of Alcohol; } 162% "

to (about) } or (about) } 1 " " 16% " 32% "

5 Cent. " 143% " 29% "

1 " " 28% " 58% "

TABLE I.--_Showing the Densities and Values of Spirits at 60 Fahr., corresponding to every Indication of Sykes' Hydrometer._

+-----------+---------+----------+--------------------+ Per Cents. of Sykes' Absolute Alcohol. Hydrometer Strength Specific +----------+---------+ Indication. per cent. Gravity. By By Measure. Weight. +-----------+---------+----------+----------+---------+ O.P. 0 670 81520 9528 9278 1 661 81715 9478 9208 2 653 81889 9431 9142 3 645 82061 9384 9078 4 636 82251 9333 9007 5 627 82441 9280 8936 6 618 82622 9229 8867 7 609 82800 9177 8799 8 600 82978 9125 8730 9 591 83151 9074 8663 10 582 83323 9023 8596 11 573 83494 8972 8530 12 564 83661 8921 8465 13 555 83827 8870 8400 14 546 83993 8817 8333 15 537 84153 8767 8270 16 527 84331 8710 8199 17 517 84509 8651 8126 18 507 84680 8595 8058 19 497 84851 8539 7989 20 487 85022 8481 7919 21 476 85205 8419 7844 22 466 85372 8361 7774 23 456 85537 8304 7707 24 446 85700 8247 7639 25 435 85878 8185 7566 26 424 86055 8121 7492 27 413 86229 8059 7419 28 402 86402 7997 7347 29 391 86574 7934 7275 30 380 86745 7871 7203 31 369 86915 7808 7132 32 357 87099 7740 7054 33 345 87282 7671 6977 34 334 87450 7608 6906 35 322 87627 7541 6832 36 310 87809 7472 6755 37 298 87988 7403 6679 38 285 88179 7329 6598 39 273 88355 7260 6523 40 260 88544 7186 6443 41 248 88716 7117 6368 42 235 88901 7043 6289 43 222 89086 6969 6210 44 209 89268 6895 6132 45 196 89451 6821 6053 46 183 89629 6747 5976 47 169 89822 6667 5892 48 156 89997 6593 5815 49 142 90182 6514 5734 50 128 90367 6434 5652 51 114 90551 6354 5570 52 100 90732 6274 5489 53 86 90913 6194 5409 54 71 91107 6109 5323 55 56 91299 6024 5238 56 42 91479 5943 5157 57 27 91666 5858 5073 58 13 91839 5778 4994 U.P. 59 03 92037 5686 4904 60 19 92228 5596 4817 61 34 92408 5510 4733 62 50 92597 5419 4646 63 67 92798 5322 4553 64 83 92984 5230 4465 65 100 93176 5136 4376 66 117 93367 5039 4284 67 135 93586 4934 4186 68 153 93758 4831 4090 69 171 93949 4729 3996 70 189 94135 4629 3904 71 208 94327 4520 3804 72 227 94518 4409 3703 73 247 94709 4296 3601 74 267 94899 4182 3498 75 288 95092 4063 3392 76 310 95288 3940 3282 77 332 95484 3810 3168 78 356 95677 3676 3050 79 381 95877 3532 2924 80 406 96068 3390 2801 81 433 96259 3241 2673 82 461 96457 3077 2532 83 491 96651 2908 2388 84 522 96846 2731 2238 85 555 97049 2539 2077 86 590 97254 2341 1911 87 625 97458 2139 1742 88 660 97660 1941 1578 89 694 97857 1746 1416 90 728 98057 1551 1256 91 761 98261 1358 1097 92 792 98452 1185 956 93 823 98657 1004 808 94 852 98866 828 665 95 880 99047 683 548 96 907 99251 525 420 97 933 99448 380 303 98 959 99658 231 184 99 982 99851 997 793 100 ... 100000 ... ... +-----------+---------+----------+----------+---------+

This Table {above} has been copied, by permission, from Loftus's 'Inland Revenue Officer's Manual,' and its correctness verified by W. H. Johnston, Esq., Surveying General Examiner.

TABLE II.--_Table for finding the Specific Gravity of any Spirit at 60 Fahr., when the Specific Gravity at any other Temperature is given._

Water taken as 1000.

+-----------------+----------+-----------------+----------+ Correction Correction Specific gravity. for each Specific gravity. for each degree. degree. +-----------------+----------+-----------------+----------+ 810 to 820 475 910 to 920 434 +-----------------+----------+-----------------+----------+ 820 " 830 473 920 " 930 424 +-----------------+----------+-----------------+----------+ 830 " 840 472 930 " 940 406 +-----------------+----------+-----------------+----------+ 840 " 850 471 940 " 950 381 +-----------------+----------+-----------------+----------+ 850 " 860 471 950 " 960 340 +-----------------+----------+-----------------+----------+ 860 " 870 466 960 " 970 269 +-----------------+----------+-----------------+----------+ 870 " 880 460 970 " 980 165 +-----------------+----------+-----------------+----------+ 880 " 890 456 980 " 990 090 +-----------------+----------+-----------------+----------+ 890 " 900 450 990 " 1000 084 +-----------------+----------+-----------------+----------+ 900 " 910 442 +-----------------+----------+-----------------+----------+

Thus, by making the proper ADDITION to the apparent strength per cent., when the observed temperature is BELOW the normal temperature of the instrument, or a corresponding SUBTRACTION, when it is ABOVE it, the strength of the sample may be determined sufficiently near for all practical purposes.

The following Table, taken from Loftus's 'Inland Revenue Officer's Manual,' will be found of great value in making these corrections, and has the merit of being easily applied.

An example will show how this Table is to be used.

_Example._--If a quant.i.ty of spirit is of the sp. gr. 894 at 73, what will be its sp. gr. at 60?

Here the sp. gr. being between 890 and 900, we must add 450 for each degree of temperature between 73 and 60. The sp. gr. at 60 would, therefore, be 894 + (450 13) = 89985. When the temperature is below 60, the correction for each degree must be subtracted. When, however, very accurate results are desired, and the necessary Tables are not accessible, the sample for trial must be brought to the normal temperature of the instrument, in the manner explained under HYDROMETRY.

_c._ From the SPECIFIC GRAVITY. The temperature having been taken by a thermometer, and the specific gravity ascertained by any of the usual methods, but preferably by means of an accurate gla.s.s hydrometer, it merely becomes necessary to refer to Table I, where, against the number expressing the specific gravity, the alcoholic content per cent., by volume, of the sample examined, will be found for 60 Fahr., subject to the corrections just referred to, when the temperature is either above or below this point.

If the precise specific gravity sought cannot be found in the _Table_, the difference between it and the next greater specific gravity must be taken for the numerator of a fraction, having for its denominator the difference between the greater and the next less specific gravity in the table. This fraction, added to the per-centage of alcohol in the fourth column of the table, opposite the greater sp. gr., will give the true per-centage sought. Thus, the sp. gr. 96051 is not in the table, and the next greater number is 96068; the former must, therefore, be deducted from the latter, and the difference (17) put as the numerator of the fraction, having for its denominator 191, the difference between 96068 and 95877. The fraction (17/191) 089, so found, added to the per-centage strength opposite 96068 in the third column, gives 33989 as the true per-centage of alcohol in the given sample.

The per-centage by volume may be converted into per-centage by weight, by multiplying the former by 793811, the sp. gr. of absolute alcohol, and dividing the product by the sp. gr. of the sample. The quotient is the number of pounds of alcohol in 100 pounds of the given spirit.

Thus:--Suppose 1000 grains by measure of alcohol to weigh 95092 grains, and to contain (see Table I) 4063 per cent. by volume of absolute alcohol, what per cent. by weight does the sample contain?

793811 4063 = 3225254093, and this product divided by 95092 = 33917, the true per-centage by weight of absolute alcohol in the sample.

2. Method based on the specific gravity, or per-centage strength by WEIGHT:--

The specific gravity is ascertained and the Table used in precisely the same manner as in the "method by volume," already described.

The per-centage by weight may be converted into per-centage by volume, by multiplying the former by the sp. gr. of the sample, and dividing the product by the sp. gr. of absolute alcohol. This is merely the reverse of the operation described above.

_Obs._ The preceding methods of alcoholometry, as well as all others depending on the sp. gr. refer to UNSWEETENED SPIRITS only; and are inapplicable to those holding sugar in solution, or any other organic matter capable of altering the sp. gr. For sweetened spirits, fermented worts, wine, beer, &c., one or other of the following processes must be adopted:--

3. Other methods, adapted to either SWEETENED or UNSWEETENED SPIRITS, Tinctures, Fermented Liquors, &c.--

_a._ By DISTILLATION as originally proposed by M. Gay-Lussac. 300 parts of the liquor under examination (measured in a graduated gla.s.s tube) are placed in a retort or small still, and a quant.i.ty exactly equal to one third (_i.e._, 100 parts), carefully drawn over; a graduated gla.s.s tube[13] being used as a receiver, and the operation stopped as soon as the distillate reaches the hundredth degree. The 'alcoholic strength' of the distilled liquor is then ascertained by any of the usual methods, and the result divided by three, when the per-centage of alcohol in the original liquor is at once obtained. If, from want of attention, more than 100 parts should be distilled over, the number which expresses the relation of the volume of the distilled product to the original bulk of the liquor tested, must be employed as the divisor. Thus, if 106 parts of liquor have distilled over (instead of 100), containing 33% of alcohol, the 300 must be divided by 106, which gives 283, and the 33% by this 283, which gives 1166%, the true proportion of alcohol in the original liquor. The strength at 'proof' may be calculated from this in the usual way.

[Footnote 13: Mulder, in his 'Chemistry of Wine' recommends this receiver to be shaped like a bottle, with its neck, or tubular part, bent at right angles above the line of its scale; and that it should be set in the centre of a gla.s.s jar kept filled with very cold water.]

To ensure accurate results, the acidity (if any) of the liquor must be neutralised with carbonate of sodium, prior to distillation. It is also advisable to add 8% or 10% of common salt to the liquor in the retort or still; this, by raising the boiling point, causes the whole of the spirit to pa.s.s over into the receiver before the distillate has reached the required measure. This applies more particularly to weak liquors. With those of greater strength (as the stronger wines), it is better to distil over 150 parts, and divide the result by 2 instead of 3. To liquors stronger than 25% by volume of alcohol, or above 52% to 54% under proof, add about an equal volume of water to the liquor in the still, and draw over a quant.i.ty equal to that of the sample tested; when the alcoholic strength of the distillate gives, without calculation, the true strength sought. To liquors stronger than 48% to 50% (14 to 12 u. p.), add thrice their bulk of water, and do not stop the process until the volume of the distillate is double that of the sample tested, when the per-centage obtained must also be doubled. In each case a proportionate quant.i.ty of salt is employed.

REVENUE METHOD. The following is the method adopted in the Inland Revenue and Customs Laboratories for the estimation of the per-centage of alcohol in wines, liqueurs, &c. A measure flask is filled up to a mark on its neck, with the wine, which is then carefully transferred to a distilling flask or retort, the traces of wine remaining in the former vessel being rinsed out with small quant.i.ties of distilled water, and the rinsings added to the wine in the latter vessel. About two thirds of the contents of the retort are then distilled over into the clean measure flask, and made up to the original bulk with distilled water, at the same temperature as the sample was previous to distillation. The strength is then taken by Sykes' hydrometer, and this (if u. p.) deducted from 100, gives the per-centage of proof spirit in the wine. Thus:--

Strength of distillate = 746 u. p. = 254 per cent. proof spirit.

_b._ From the TEMPERATURE of the VAPOUR, as originally proposed by Groning. The bulb of a thermometer is thrust through a cork into the head of the still, or other vessel employed, and the temperature of the vapour in which it is immersed being noted, is sought in the following table:--

TABLE III.--_Showing the Alcoholic Content, by_ VOLUME_, of Boiling Spirits, and of their Vapour, from the Temperature of the latter, as observed by a Thermometer._ By GRoNING.

+---------------+-------------------+-------------------+----------------+-------------------+------------------+ Temperature of Alcoholic content Alcoholic content Temperature of Alcoholic content Alcoholic content the Vapour. of the Distillate of the Boiling the Vapour. of the Distillate of the Boiling Fahr. per cent. Liquid per cent. Fahr. per cent. Liquid per cent. +---------------+-------------------+-------------------+----------------+-------------------+------------------+ 1700 93 92 1898 71 20 1718 92 90 1920 68 18 1720 91 85 1940 66 15 1728 90-1/2 80 1964 61 12 1740 90 75 1986 55 10 1746 89 70 2010 50 7 1760 87 65 2030 42 5 1783 85 50 2054 36 3 1808 82 40 2077 28 2 1830 80 35 2100 13 1 1850 78 30 2120 0 0 1874 76 25 +---------------+-------------------+-------------------+----------------+-------------------+------------------+

This method is admirably adapted to the purposes of the distiller and rectifier, as it furnishes a ready means of approximately determining the strength of the spirit pa.s.sing over, at every part of the process of distillation, as well as that of the wash left in the still.

_c._ From the BOILING POINT, as originally proposed by M. l'Abbe Brossard-Vidal. This method is founded on the fact, that the boiling points of mixtures of alcohol and water, unlike water alone, are scarcely disturbed by the addition of saline, saccharine, or extractive matter within certain limits. It hence offers a ready means of determining the proportion of alcohol present in spirits, wines, fermented liquors, &c., with sufficient accuracy for all ordinary purposes. In applying it, a thermometer, with a large bulb and a narrow bore, and a movable scale graduated from 180 to 212 Fahr., is usually employed. Before using it as an alcoholometer, it is set, with its bulb immersed, in a small metallic boiler (bra.s.s or copper) containing distilled water, which is then raised to the boiling-point, and the 212 of the scale accurately adjusted on a level with the surface of the mercury, should it vary from that point.

This is necessary on account of variations of atmospheric pressure causing corresponding variations of the boiling-points of liquids. It is then ready for several hours' operations, and, generally, for an entire business day, without further adjustment. The little boiler is next filled with the liquor to be examined, and the lamp again lighted. The temperature as shown by the scale of the instrument at the commencement of full ebullition being ascertained, may be sought in one of the following _Tables_, against which the alcoholic content of the liquor will be found (nearly).

TABLE IV.--_Exhibiting the_ BOILING POINTS _of Mixtures of Alcohol and Water of the given strengths._ By GRoNING.