are so characteristic that the colouring of malt in complex mixtures can be discovered by them. In barley the colour does not exist.

The carbonised or high-dried malt, used to colour porters and dark beers, contains at least two colouring-matters different from that just described. The one is orange-yellow, soluble in water and strong alcohol; it gives no flesh-coloured precipitate with sodic hypochlorite and citric acid, nor does it (like the hop colouring-matters) darken by oxidising agents; it is therefore probably a caramel. The other substance may be separated as follows:-The beer is evaporated to a small bulk, and precipitated by alcohol; the colour is thrown down, mixed with gum, and by redissolving and reprecipitating it can ultimately be obtained nearly pure. In aqueous solution it gives an orange-brown spectrum, which is very slightly shaded from D E, moderately dark to E and C, after that very dark. A sugar, "maltose," is obtained by the action of malt extract on starch; it has a specific rotatory power of + 150°. The behaviour of maltose to Fehling's solution, and its method of estimation, is described at p. 116. It forms a hard, white, crystalline mass, consisting of needles, which lose their water in a current of air at 100°.

§ 258. Beer Bitters.-Beer, bittered by the hop alone, when precipitated by acetate of lead, filtered, and the excess of lead removed by hydric sulphide, gives a filtrate destitute of bitter taste; while, on the contrary, if it has a bitter taste, some bitter other than hop has been used. Whether such bitter is an adulteration or not, will depend altogether on the nature of the substance added; for since the repeal of the hop duty in 1862, and the consequent return of the trade to other bitters, anything harmless in the way of a bitter is perfectly legal. If, however, such poisons as picric acid, picrotoxin, or colchicine, should be found, there can be no difference of opinion as to the course the analyst should pursue.

With regard to these, picric acid has certainly been discovered, and picrotoxin is strongly suspected, but as yet the latter has not been proved to be a common adulterant. The so-called discovery of colchicine in beer appears to have been throughout a mistake. A sample of beer of unknown origin was found to contain a bitter amorphous substance, soluble in water and alcohol, and capable of separation from its acid watery solution by either chloroform or ether. Nitric acid of 148 dissolved it with a fine reddish colour, and a mixture of nitric and sulphuric acids turned it rose-red. H. Van Geldern* finds that the body

*Arch. Pharm., 3, ix. 32.

which gives these reactions originates in the hop, and that the reactions are only produced in the presence of gelatine; and further, that a mixture of unadulterated hops and gelatine gives all the reactions of colchicine. This observation is quite as important to the toxicologist as to the food analyst.*

§ 259. Hops.-Hops are the catkins of the Humulus lupulus, and consist of imbricated scales enclosing the so-called nut. The scales themselves are covered with aromatic superficial glands, which are designated "yellow powder," or lupulin. Freed as

far as possible from the lupulinic grains, the scales consist of astringent matter, chlorophyll, gum, colouring-matter, and ash. The lupulin itself, according to Dr. Yves, contains the following

matters:

This analysis does not include the oil of hops, which is a very important constituent of the hop, and may be obtained by distilling the fresh flowers or the lupulin.

The resin and bitter principle of the hop are to the brewer the most important constituents, its commercial value being directly dependent on them. According to some recent analyses made by Mr. Porter, the substances capable of solution in ether (viz., the oil, resin, and bitter principle) vary in different samples from 8.8 to a little over 17 per cent.†

Lupulite, or true Lupulin (a substance isolated by Lermer in 1863), can be obtained in rhombic prisms by treating fresh hops with four times their weight of ether, distilling the ether off, then adding to the extract alcohol of 90 per cent. (which leaves the wax undissolved), and again taking up the alcoholic extract with ether. The ethereal solution is repeatedly shaken with strong potash-lye to get rid of the resin, and lastly with pure

*

Phospho-molybdic acid gives a thick yellow precipitate with lupuline. On adding ammonia, and placing in a watch-glass, the precipitate becomes surrounded by a blue zone. Colchicine behaves in a similar way.-Zeitschrift für Analyt. Chemie, 1880, p. 106.

+ On the Examination of Hops, by W. E. Porter, F.C.S. August, 1877; January, 1878.

Analyst,

water to take up the bitter matter. It is precipitated from the aqueous solution by sulphate of copper, the composition of the precipitate being CHCuO4; and crystals are obtained by dissolving the precipitate in ether, decomposing with SH, and evaporating the ethereal filtrate in a stream of carbonic acid gas.

A principle very bitter, but not crystalline, can also be obtained by adding to the aqueous extract of the lupulin grains a little lime, and then treating with alcohol. The solution is to be evaporated, the mass treated with water, and the solution again evaporated to dryness. On washing this residue with ether, a white uncrystallisable, bitter principle-soluble in 20 parts of water, very soluble in alcohol, and but slightly so in ether-is obtained; it is probably a derivative of Lermer's lupulite.

Lermer's Lupulite crystallises in glittering, rhombic, brittle prisms, tasteless in themselves, but with a very bitter flavour, and an acid reaction when dissolved in alcohol. They are insoluble in water, but dissolve easily in alcohol, ether, chloroform, bisulphide of carbon, benzole, and turpentine; exposed to the air, they soon become yellow and partly amorphous.

TABLE XXXVIII.-CONSTITUENTS OF THE ASH OF HOP CONES.

The ash of the hop differs but little from the ashes of foliar organs generally, the relative proportion of each constituent varying within somewhat wide limits, according to the particular variety. (See accompanying table.)

Oil of Hops, according to the researches of Wagner, consists chiefly of an oxygen-holding oil, CH180, containing in solution a camphor boiling at 175°. The specific gravity of the oil itself is 0.968. It begins to boil at 125°, and successive portions can be separated by fractional distillation, the last passing over at 235°; one-sixth distils over between 125° and 175°, and is of a pale colour and quite clear; about half passes over between 175° and 225°, and is also very clear; but the remainder is yellow, and the residue in the retort has the appearance of a brown turpentine.

The crude oil is brownish-yellow, and very sparingly soluble in water, one part requiring more than 600 times its weight for complete solution. It does not contain sulphur, as previously asserted by Payen and Chevallier, nor does it reduce ammoniacal solution of silver. Oxidation by nitric acid produces valerianic acid and a yellow acid resin; if dropped on melted caustic potash, valerianate, carbonate of potash, and a hydrocarbon are the results. The oil appears to be neither narcotic nor poisonous, twenty drops having had no action whatever on a kitten (W. Keil); but the wonderful preservative properties ascribed to it by older writers are very problematical.

M. Issleib has recently made a careful examination of the bitter principles of the hop. His method of separation was to extract with cold water, and then to treat the cold extract with animal charcoal, exhausting the latter after drying with 90 per cent. alcohol. This gave a yellow solution, from which a brown resin was precipitated on concentration, leaving in solution the bitter principle and another substance (C). The bitter may be removed by ether, and is pale yellow, amorphous, non-nitrogenous, and slightly acid, and is dissolved by alkalies with the production of a fine yellow colour. He ascribes to it the composition of C9H16010, and states that it splits up under the influence of sulphuric acid, thus

29

46

Bitter Principle.
2C29H46010

+ 3H2O

Lupuliretin.
C10H1604 +

Lupulic Acid.
C40H82019

The resin has the composition of C10H24O31, and is presumed to be formed by the oxidation of oil of hops; lastly, the substance C is considered to be an oxidation product of the oil of hops, and has the composition of C10H1806

* Arch. Pharm., [3],16,345–363; Journ. Chem. Soc., March, 1881.

A few other bitter principles, some of which have actually been found, and the remainder are supposed to exist, may be now conveniently described. (For Picrotoxin and Colchicine the reader is referred to the second volume of this work.)*

§ 260. Absynthin, CHOHO.—The bitter principle of wormwood, Artemisia absynthium. It may be extracted from the hot aqueous extract of wormwood by precipitation with tannic acid, evaporating the tannate to dryness with oxide of lead, and extracting the dried residue by alcohol, and subsequent purification with animal charcoal. Absynthin dissolves easily in alcohol and ether, with difficulty in hot water, and is scarcely soluble in cold. When obtained from alcoholic solution it is usually in the form of pale-yellow drops, which gradually become crystalline; it has a peculiar odour and extremely bitter taste, and its reaction is neutral. It reduces a hot ammoniacal solution of silver nitrate, but an alkaline tartrate of copper solution remains unchanged by it. It is dissolved by caustic potash with the production of a brown colour. Concentrated sulphuric acid produces first a brown colour, passing into a green-blue; as water is added, the colour becomes darker, until grey flocculent particles are separated. Boiling with dilute acids produces resinous products, but no sugar.

The bitter principle, according to some observers, is a direct cerebral excitant; according to others, a pure tonic. It is used occasionally in medicine, in doses from grain to 2 grains, and the herb producing it is officinal in the Continental pharmacopœias.†

15

17

$261. Aloin-CHO, (TILDEN), CHO, (STENHOUSE), CH1607 (E. SCHMIDT)-may be obtained by treating aloes with dilute sulphuric acid, removing the deposit of resin, and evaporating to a syrup. The crystals thus obtained are yellow needles, soluble in water and alcohol, and possessing a bitter taste. amount of crystallisation water varies from 5.89 to 14:29 per

*

Bibliography.

The

LERMER-Dingl. Polytech. Journ., clxix. 54; Viertelj. Pract. Pharm.,

xii. 505.

PAREIRA'S "Materia Medica."

HUSEMANN.- -"Die Pflanzenstoffe," &c.

PAYEN and CHEVALLIER.-Journ. Pharm., [2], viii. 214, 533. PERSONNE.-Journ. Pharm., [3], xxvj. 241, 329; xxvj. 22. +KROMAYER.-Arch. Pharm., [3], cviii. 129.

LEONARDI.-Osservazioni ed esperienze del Dott. Lupis sopra la virtù antifebrile dell estratto amarissimo d'assenzio, &c. Milano, 1828. LUCK.-Ann. Chem. Pharm., liv. 112; lxxviii. 87.

RIGHINI.-Journ. Chim. Méd., xix, 383; Journ. Chim. Méd., 2e ser., ix. 383.