From the malt extract the amount of malt used is calculated, 32-0 of malt equalling 210 of extract; or, instead of referring to the malt extract tables, 1000 may be subtracted from the original gravity, and the remainder multiplied by 0025, which will equal the total amount of malt extract per gallon in pounds weight.

This spirit indication, on reference to Table XLI., equals 26.0

Now, on reference to Table XL., 1.0402 correspond to 9.950 parts of extract in 100, or 9950 lb. per gallon.

which does not materially differ from the amount obtained from the tables.

(2.) A beer, by the evaporation process, indicated 6.1 per cent. of alcohol. On reference to the specific gravity table (Table XXXIII.), p. 468, the specific gravity corresponding to this strength is 9896.

This, according to Table XLII., corresponds to 47.1;

corresponding, according to Table XL., to 1-5441 lbs. of malt

extract to the gallon. The amount of malt used in the two examples is found thus

If the beer should have a somewhat large proportion of acetic acid (as in old and hard beers), it will be necessary to take into account the loss of gravity by acetic acid. This complicates the calculation, and is only occasionally required.

The loss of gravity by acetic acid is obtained by the use of Table XLIII. Let us suppose 36 per cent. of acetic acid to have been found in Example 1; from this subtract 10 per cent., the amount which may be taken as incidental to healthy fermentation, and allowed for in the table. Thus,

This 26, according to the table, equals 34, the number to be added to the spirit indication.

6.74

Total spirit indication,

The rest of the calculation is as before.

It may be desirable to examine the malt extract further, and specially with a view to ascertaining whether grape sugar has been used in place of malt or not. This may be done, according to Haarstick, by taking advantage of the fact that most, perhaps all, of the grape sugars of commerce contain Béchamp's amylin, a substance of great rotatory power, and one, moreover, not destroyed by fermentation.

The samples of beer were examined by Haarstick as follows:1 litre of beer was evaporated to a syrup, to which alcohol of 90 per cent. was added, drop by drop, from a burette with constant agitation, until a volume of about 300 cc. had been used. The separation of dextrin was completed with 95 per cent. alcohol, until the filtrate did not show the least turbidity when mixed with an equal bulk of 95 per cent. alcohol. The mixture * Or, of course, the factor 7 1.524 may be used, and then the two equations are as follows:-(1.) ·995 × 1·524=1516, and (2.) 1·5441 × 1·524 = 2·3532.

=

was then left at rest for twelve hours, filtered, and the greater part of the alcohol distilled off. The remainder was evaporated to dryness on a water-bath, the solid portion dissolved in distilled water, and the solution diluted to a litre, and fermented with yeast at 20°, until all the sugar had been destroyed. The fermentation was completed on the fourth day, and the result of the process was, that beers prepared without grape sugar gave a solution of no rotatory power, while those prepared with grape sugar turned the plane of polarisation 2°·0 to 3°4 to the right, as observed in Hoppe's scale.

(5.) The Hop Resin and Glycerin.—Griessmayer* estimates the hop resin and glycerin by concentrating the beer to one-third of its bulk, and shaking it up with petroleum ether; this, on separation and evaporation, leaves the hop resin. The liquid, now freed from hop constituents, is made alkaline by baryta water, or, better, by barium alcoholate, and shaken up several times with a mixture of two parts of alcohol and three of ether; the latter, on being separated and evaporated in the usual way, leaves the glycerin.

Clausnizert gives, as the result of his elaborate experiments on the various processes for the estimation of glycerin, the following method, which would appear to be the best hitherto published: 50 cc. of beer are warmed on the water bath to get rid of CO2, and then mixed with 3 grms. of hydrate of lime and evaporated to a syrup; 10 grms. of powdered marble are then added, the mass frequently stirred, and the whole dried on the water-bath. The dish with its contents is now weighed, and an aliquot part (about two-fifths to three-quarters) put in the extraction apparatus figured at p. 68, and exhausted with 20 cc. of alcohol of 80 to 90 per cent. The alcoholic extract (now about 15 cc.) is mixed with 25 cc. of anhydrous ether, the precipitate separated, and the ether-alcohol received into a weighed flask, the precipitate also being washed with alcohol-ether [2: 3.] The almost colourless filtrate is freed from alcohol and ether by very slow evaporation. Lastly the glycerin is dried at 100° until in two hours no more than 2 mgrms. are lost. This process will take from two to four hours for normal beer, from four to six for beer to which glycerin has been added. It may be well to burn up the glycerin and subtract the ash found. Clausnizer gives the percentage of glycerin in common German beers as follows::

Deut. Chem. Ges. Ber., xi. 292, 293.

Clausnizer, F.: Zur Glycerine Bestimmung in Bier. Zeitschrift für analytische Chem., xx. 80.

(6.) The Nature of the Bitter used.—This is the most difficult part of the investigation, and requires a very considerable amount of practical knowledge. Occasionally, if the beer is put in the tube figured at p. 502, small fragments of quassia, calumba, and similar substances will be observed to sink to the bottom as a sediment, and may be detected microscopically; indeed, it is probable that were it possible to obtain the sediment from the beer casks, many foreign matters might in this way be detected.

In most cases it is sufficient to use some of the special processes hereafter described, and restrict the inquiry to proving the absence of picric acid, of picrotoxin, and of any other specially noxious substance which may be suspected. Should, however, the analyst desire to examine the beer generally for various organic principles, the elaborate process as worked out by Dragendorff and others, fully described in the author's work on "Poisons," must be used. About 600 to 1000 cc. of the beer are evaporated to a syrupy consistence, and sufficient strong alcohol is added to precipitate the dextrin. The whole is filtered, and after standing some hours, the filtrate, acidulated with sulphuric acid, and shaken up successively with petroleum ether, benzine, chloroform, and (if salicin be sought) amylic alcohol.

Or the beer may be precipitated with acetate of lead, filtered, the excess of lead thrown out by sulphuric acid, and treated with the solvents as described. If inquiry be made as to the nature of the residue left by these different solvents in beer simply made from hops and malt, it appears that

(1.) The petroleum ether extracts—

(a.) An amorphous, slightly bitter substance, soluble in ether and alcohol, and partially soluble in water; this is derived from both hops and malt; (b) A substance precipitable by basic acetate of lead; and one (c.) Becoming red by Fröhde's reagent; both derived from the hop. (d.) A substance derived from the hop alone, becoming red with sulphuric acid and sugar.

(2.) Benzine extracts the same substances, and in addition— (e.) A substance derived from the hop, which precipitates tannin;

* E. Borgmann (Zeitschr. anal. Chem., xxii., 533, 534) gives very different results, for in the examination of a large number of beers, both German and English, he found the ratio of alcohol and glycerin to average 100 alcohol : 4.8 glycerin the extremes were 100 and 100. Glycerin can be estimated in beer also by Wanklyn's process (see p. 371).

55