apothecary-the amateur. They shall find that the 48 pages of "THE CHEMIST will contain everything, and that they will not need to purchase any other chemical journal. We intend to give, in our closely-printed pages, as much matter in one month as other periodicals do in three. Our readers will learn with pleasure that we intend to exert ourselves very energetically in bringing to light, in a chemical point of view, the industrial resources of Ireland—a country in which many manufactures might be carried on with even greater advantage than in England; and if its capacity for manufactures were fully developed, it would speedily become one of the wealthiest, as it certainly is the most beautiful, country in the world. We speak from an intimate knowledge of this part of the United Kingdom. We hope that the day is not far distant when men of practical knowledge will bring their capital and knowledge to Ireland, as to a country in which they may be employed with advantage to themselves, and to the thousands of good-humored, willing, but famishing, peasantry, who are now eagerly seeking work all over the world, there being none to employ them at home. Englishmen of knowledge and capital, generally, are not aware of the extent to which they could CREATE manufactures in this country. It must not he supposed that there is any lack of desire on the part of the people of Ireland; it is merely want of opportunity. The Medical Schoo's of Dublin are inferior to none in the United Kingdom; the professors are all men of talent and extensive professional experience; the hospitals are numerous and wellregulated. No city of its size can boast of more eminent medical practitioners, and there are scientific chemists whose names are known wherever the English language is spoken, and from whom we hope to receive occasional contributions. In Scotland we have many friends who will hail with delight the re-appearance of “THE CHEMIST;" and we hope that our pages will be from time to time enriched with articles by some of its many celebrated men. Among other matters, we shall devote considerable attention to the sanitary question, at all times of the most serious importance, but especially so at a time when the Almighty has inflicted on these countries a malignant epidemic of which thousands are dying every weeknot alone of the unfortunate poor, who, badly clothed and fed, and lodged in tenements to pass which offends the olfactory nerves most powerfully-but among the upper classes, sparing neither rank, wit, nor beauty, any more than wretchedness, destitution, and filth. THE CHEMIST. [NEW SERIES.] I. CHEMISTRY. MEMOIR ON COFFEE.* BY M. PAYEN. PAYSSÉ, Chenevix, Cadet de Vaux and Cadet de Gassicourt, examined the composition of coffee, without isolating any of its proximate principles; Runge discovered, and Robiquet studied, caffeïne, a crystallisable nitrogenous substance: Robiquet observed in coffee two fatty substances, one of which appeared to him analogous to the resins. A skilful German chemist, Rochleder, examined, in 1844, the fatty matters of coffee: he extracted from it palmitic and oleic acids; he showed that coffee does not contain resin; and he noticed the presence of a nitrogenous substance-legumine. The resisting tissue appeared to him to be formed of one of the ligneous substances which I have made known. Notwithstanding the efforts of the scientific men I have named, the chemical knowledge attached to this important product left much to be desired. I have endeavored to extend it. ORGANOGRAPHIC EXAMINATION. The resisting mass, of a horny appearance, forming the perisperm or endosperm of these berries freed from their pericarp, presents under the microscope a tissue of juxtaposed cellules, with thick sides indented with irregular cavities, communicating with one another by small openings. The thick sides, disaggregated by sulphuric acid in presence of iodine, acquired the blue color which denotes cellulose, then formed a gummy solution indicating dextrine. The agglomerated organic corpuscules, colored orange by these re-agents, * Annales de Chimie et de Physique, xxvi., 108. VOL. I.-No I., October, 1849. showed, with their nitrogeno us composition: -1. A peripheric cuticle covering, in all their folds, the surfaces of the perisperm. 2. The spongy nitrogenous substances filling the epidermic cellules, and containing oleïform matters. 3. In the more internal cellules, analogous granular bodies, containing fatty substances. 4. Lamelliform membranes, injected with nitrogenous matters, in the intercellular meati. PROXIMATE ANALYSIS, The coffee should first be reduced to a powder by means of a mill or a pestle and mortar; it is afterwards exhausted with ether in a displacement and continuous distillation apparatus. The ethereal solution gives, on approaching to dryness, a fatty matter, which may be separated by washing with boiling water. The aqueous solutions, mixed, leave a brown or fawn colored residue, which, treated with anhydrous alcohol,* yields, after evaporation, a crystalline deposit, which, washed twice in cold alcohol, dissolved twice in boiling alcohol and crystallised, gives caffeïne in distinct, white, brilliant prisms. Pure caffeïne thus obtained for the first time directly, is fusible by heat and volatile without residue; its vapors, condensed, reproduced crystals sublimed in colorless and diaphonous prisms. It gave, in four analyses, numbers differing but little from the admitted composition. Its elementary composition and its equivalent weight, hitherto undetermined, would correspond to the following formula: The portion of the aqueous extract which does not dissolve in anhydrous alcohol contains a small quantity of a new crystallisable compound of legumine and another nitrogenous matter. Coffee exhausted by ether was very carefully washed with alcohol of 0.60; the solutions, added together, were of a rather syrupy consistence: three times their bulk of alcohol was added to them. The liquid separated into two parts: one was viscid, and deposited; the other was very fluid. The latter, which contained the greater part of the new crystallisable compound, was decanted. It may be detected by putting a small quantity of the solution in a tube, and adding a drop of ammonia: the yellow color, verging on green, and that becoming gradually more intense, is a certain indication of this fact; it led to the process about to be described, and also served as a guide in the ulterior operations, when, having mother liquors to treat, it was necessary to eliminate by means of alcohol foreign substances from the compound just obtained. To take from the different precipitates a portion of the crystallisable compound, it is sufficient to dissolve them in a small quantity of water, then to precipitate it again by means of alcohol of 0.85 or 0.90; the supernatant liquor removes from the solution the substance sought. All the alcoholic solutions were distilled on a sand bath. The syrupy residue was diluted with 0.25 of its bulk of alcohol at 0.90. Put into a cool place, it gave, after 24 or 48 hours, granular crystals, which were collected in a filter and purified with cold alcohol at 0.65; they were washed on a filter with alcohol of 0.70 to 0.85. They were then re-dissolved to saturation in alcohol of 0.6, the mixture being heated in the sand bath. Cooling gives abundant and almost pure crystals: these are prisms grouped in spheroids by the re-union of one of their ends in a common centre. The purification is finished by re-dissolving in alcohol and re-crystallising twice. Finally, it is allowed to drain, and dried in vacuo at 230° F.* PROPERTIES AND COMPOSITION OF THE CRYSTALLINE SUBSTANCES OF COFFEE. The properties manifested by certain reactions on this substance could not be comprehended without first knowing its composition. The colorless principle of the rich green coloration resides in the acid, which I call, for this reason, chloroginic acid. The crystallisable compound, or natural salt of coffee, is a double chloroginate of potassa and caffeine. If it be rubbed when it has just been dried at 212° F. on a warm sheet of paper, it is electrified so as to adhere to the blade of a knife presented to it, and so as to maintain the form of long, bulky flocks. alteration up to 300° F.; but towards 365° When exposed to heat, it undergoes no F., it fuses, developes a beautiful yellow color, boils, swells up to such an extent as to occupy five times its original space, and remains spongy, yellowish, solid, and friable. When heated to 450° F., it becomes brown; it is then partially decomposed. The vapors which are disengaged from it give, in condensing, crystals of caffeïne in needles. If it be heated further, the brown color becomes deeper, a fresh liquefaction takes place, abundant alkaline vapors are exhaled, the mass swells up again, so to assume four times its bulk, or twenty times that of the crystals employed. The very light charcoal thus obtained has an iridescent surface.* as It is, doubtless, to the presence of the chloroginate interposed in the cellulose of the perisperm that the swelling of coffee berries in roasting must be attributed. This double salt is very slightly soluble in anhydrous alcohol, even with the aid of heat. Its saturated solution in alcohol of 95°, made with the aid of heat, allows it to crys tallise, by cooling, in prisms radiating from cohol of 85°, its crystallisation from it on common centres. Being more soluble in alcooling is more abundant: the solubility increases with the dilution of the alcohol. Pure water dissolves still more of it, and this solution saturated with heat cools in the form of a mass. The cold solution, evaporated in a capsule, gradually separates a *Throughout the processes which have crown of very fine crystals in groups. The for their object the extraction and purifica-aqueous solution, even during crystallisation, tion of the new crystallisable compound, is decomposed in the air, becoming first yeldistilled water, free from air and traces of low, and then greenish brown. ammonia, must be used; the same water must be used for diluting the alcohol to the various degrees required; finally, it is necessary to keep the solutions in vacuo or under receivers, with shallow vessels of sulphuric acid. Crystals of double chloroginate, gently *The phenomena here pointed out were observed in operating on 1 decigramme of salt in a tube 5 millimetres in diameter and Om. 12 in length. heated in contact with potassa, become of a vermillion or orange red; heated further, the mixture fuses, takes a yellow color, disengages abundant ammoniacal vapors, becomes brown, &c. Heated with monohydrated sulphuric acid, the natural salt of coffee developes an intense violet color and a bronzy pellicle. Hydrochloric acid produces analogous phenomena; under the influence of nitric acid an orange red color is manifested. In solutions of the double chloroginate, acetate of lead gives a floculent, pale greenish yellow. The tribasic acetate produces a precipitate of similar form, but of a pure yellow color. Nitrate of silver, alone, does not produce any change, but, previously mixed with a very small quantity of ammonia, it gives a yellow color which inclines to brown; the liquor becomes turbid; a pellicle of reduced metallic silver very soon appears on the surface, and gradually extends to the sides of the vessel. The proximate analysis of the double salt may be performed by several processes; the potassa is determined by incineration, and is represented by 0.11 of carbonate, or by the conversion of this salt into sulphate. The compound dissolved and treated by a quantity of sulphuric acid equivalent to the potassa, then evaporated in contact with powdered marble, gives sulphate of potassa mixed with an acid chloroginate of caffeïne. Alcohol removes this organic compound whose acid may be precipitated by subacetate of lead. The caffeine is extracted from the supernatant liquor, by washing the residue with cold alcohol, and treating what remains with hot alcohol; the latter, on cooling, deposits caffeïne in crystals. The chloroginate of lead may also be obtained either by precipitating the alcoholic solution of the normal salt with tribasic acetate of lead and washing the precipitate, or by triturating the same salt, without heat, with an excess of protoxide of lead and water. In the latter case, the potassa left in the mixture renders the chloroginate of lead soluble, forming, doubtless, another double compound; but the disunion of the parts may be effected by a current of carbonic acid introduced into the filtered liquid. This solution retains the potassa and caffeïne. The latter may be extracted by evaporating to dryness, washing the residue with cold alcohol, then dissolving the caffeïne in boiling alcohol, which, after filtration, makes its appearance, filling with its crossed needles the entire height of the liquid. A fourth means, which is much longer, of extracting the caffeine from the double salt, consists in producing an alteration of chloro ginic acid under the combined influences of water, air, and ammonia. One gramme of the natural compound is dissolved in ten cubic centimetres of water; two or three drops of ammonia are added, and it is placed in a flat capsule under a bell glass in which the air is very slowly renewed. The yellow, green, and blueish green colors succeed in twenty-four hours; then the mixture acquires a brown tint. A little water is occasionally added to compensate for evaporation. After twenty or thirty days the conversion is finished; it is evaporated to dryness, and a very deep brown residue is obtained, which, detached in scales, powdered, and treated with boiling anhydrous alcohol, first dissolves and then crystallises the caffeine by cooling. The alteration of the double salt by heat, carried only far enough to turn the swelled-up matter slightly brown, also enables us to extract a considerable portion of the caffeine by means of boiling anhydrous alcohol. EXTRACTION AND PROPERTIES OF CHLOROGINIC ACID. Chloroginate of lead, completely purified by washing with boiled distilled water, and decomposed by a current of sulphuretted hydrogen, gives a solution which, rapidly evaporated, permits a confused crystallisation of chloroginic acid. This acid, purified by small quantities of anhydrous alcohol, is white, soluble in anhydrous alcohol, more soluble in dilute alcohol, very soluble in water, and difficultly crystallisable. Its aqueous solution, almost saturated at the boiling temperature, crystallises only very slowly in microscopic prisms radiating from common centres, presenting, after 20 or 30 days, numerous agglomerations of spherules of one or two millimetres in diameter. Chloroginic acid dissolved in water has a very acid re-action; it powerfully reddens litmus paper; it is the active principle in the different colorings noticed above in the natural salt of coffee. Heated in a tube, it fuses, turns yellow, boils, and leaves a thin shining layer of charcoal; its vapor condenses into a brown liquid, which, rapidly heated, leaves a very thin iridescent layer of charcoal. The elementary analyses of chloroginic acid, of the double chloroginate of potassa and caffeïne, and of chloroginate of lead, gave the following results:Chloroginic Acid. Carbon .... Hydrogen Oxygen .... 56.0 5.6 38.4 100.0 'Chloroginate of Potassa and Caffeine. Carbon .... Hydrogen Nitrogen Potassa... roginate. Chloroginic acid Potassa.... 50.74 5.38 9.12 7.50 Proximate Composition of the Double Chlo Caffeïne.. 63.5 7.5 29 0 100.0 which precede and accompany the acts of nutrition it guides our senses, and, however fugitive or diversified it may be, it still leaves an impression on the memory capable of influencing our selection in the presence of many kinds of food. M. Chevreul, in a special report, has shown how we should take account of the aroma and taste of broth, and by what means they may be developed. It is among the volatile acids, the etheriform or alcoholic compounds, the dif Proximate Composition of Chloroginate of ferent substances carried Equivalent Weight of Chloroginate of Lead. with the view of applications, to extract, Undoubtedly a greater number of analyses of the various compounds are required in order to establish definitively the composition and formulæ of chloroginic acid and of the chloroginates; but the following facts will remain demonstrated, independently of any further verification : 1. A portion only of caffeine is in the free state in coffee; it may be extracted directly, without heat, and very pure. 2. Caffeine fulfils a basic part in the composition of the natural double salt. 3. The alterations of the organic acid, whether spontaneous or produced by an elevation of temperature, set caffeine at liberty, and leave, combined with the potassa, a brown acid, the product of the ultimate transformation. 4. The double salt pre-exists in the normal state in the perisperm of coffee berries. 5. Among the curious properties of chloroginic acid, the remarkable power which it possesses of developing a very intense green color adds interest to the discovery of the crystallisable compounds which its rapid and variable transformations had hitherto caused to be overlooked. AROMATIC ESSENCE OF COFFEE. Among the properties which distinguish our aliments, one of the most importantthe aroma which these substances exhaleperforms a great part in the phenomena study, and weigh these odoriferous bodies. In the hope of attaining this object, and availing myself of the skilful co-operation of M. Poinsot, I made a great number of distillations of several commercial kinds of coffee, roasted at different degrees, in glass apparatus, fractioning the products; the latter were condensed at several temperatures, from 194° F. to from 4 to 6 below the freezing point of water. The infusion obtained by means of warm water poured on ground coffee, in the proportion of one quart of water to 100 grammes of coffee, was put into the first flask of the apparatus; after two hours' boiling it did not retain any agreeable odor; the first receiver, whose temperature was gradually raised by the condensation of the vapor from 77° F. to 194° F., contained distilled water occupying 0.1 of the bulk of the infusion, On this water, which was of a slightly yellow color, floated a few drops of a concrete white essence; this essence, like the rest of the distilled liquid, was almost entirely deprived of the agreeable aroma, whose traces might be confounded with the odor developed by several animal matters altered by boiling. The second receiver, maintained at the temperature of 77° to 86° F., had received scarcely 001 of the bulk of the infusion in the form of a liquid, which was distilled when the temperature of the first receiver had been allowed to rise to 194° F. This liquid, on which floated minute quantities of concrete essence, exhaled an agreeable aromatic odor, resembling that of coffee itself, but so |