4 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. purification is finished by re-dissolving in alcohol and re-crystallising twice. Finally; The 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. coloration resides in the acid, which I call, The colorless principle of the rich green for this reason, chloroginic acid. The crystallisable compound, or natural salt of coffee, feine. If it be rubbed when it has just been is a double chloroginate of potassa and cafdried 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 caffeine 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 as to assume four times its bulk, or twenty times that of the crystals employed. The very light charcoal thus obtained has an iridescent surface.* 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 crystallise, 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. this solution saturated with heat cools in the Pure water dissolves still more of it, and form of a mass. The cold solution, evaporated in a capsule, gradually separates a crown of very fine crystals in groups. The aqueous solution, even during crystallisation, is decomposed in the air, becoming first yellow, and then greenish brown. Crystals of double chloroginate, gently *Throughout the processes which have for their object the extraction and purification of the new crystallisable compound, distilled water, free from air and traces of ammonia, must be used; the same water must be used for diluting the alcohol to the various degrees required; finally, it is ne- *The phenomena here pointed out were cessary to keep the solutions in vacuo or observed in operating on I decigramme of der receivers, with shallow vessels of sul-salt in a tube 5 millimetres in diameter and ric acid. 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 green ish 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 sait 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 caffeine. 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 caffeïne 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 for 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 beated, leaves a very thin iridescent layer of charcoal. The elementary analyses of chloroginic acid, of the double chloroginate of potassa and caffeine, and of chloroginate of lead, gave the following results :Chloroginic Acid. 186 100.000 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.* * Throughout the processes which have for their object the extraction and purification of the new crystallisable compound, distilled water, free from air and traces of 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. THE PROPERTIES AND COMPOSITION OF 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, feine. If it be rubbed when it has just been is a double chloroginate of potassa and cafdried 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 caffeine 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 crystallise, 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 crown of very fine crystals in groups. The aqueous solution, even during crystallisation, is decomposed in the air, becoming first yellow, and then greenish brown. 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 sait 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 caffeïne 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 for enough to turn the swelled-up matter slightly brown, also enables us to extract a considerable portion of the caffeïne 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 38.4 100.0 100.0 which precede and accompany the acts of M. Chevreul, in a special report, has It is among the volatile acids, the etheriform or alcoholic compounds, the dif Proximate Composition of Chloroginate of ferent substances carried away by the Lead. 40.0 100.0 Undoubtedly a greater number of analyses of the various compounds are required in order to establish definitively the composition and formula 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 nor mal 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 ammoniacal and aqueous vapors, and still Coffee contains aromatic essences, which the fat oil obtained by the processes described above powerfully retains; the aromatic properties are modified by torrefaction, however slight. It was in this state that it was desirable, with the view of applications, to extract, 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 01 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 0 01 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 exhaled which floated minute quantities of concrete an agreeable aromatic essence, odor, resembling that of coffee itself, but so |