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96 or 50.855 | PROPERTIES AND COMPOSITION OF THE 10 , 5.085 CRYSTALLINE SUBSTANCES OF COFFEE,
56, 30.000 03............ 24 ,, 14.060
The properties manifested by certain re
actions on this substance could not be com186 100.000
prehended without first knowing its comCoffee exhausted by ether was very care
position. fully washed with alcohol of 0.60; the
The colorless principle of the rich green solutions, added together, were of a rather
coloration resides in the acid, which I call,
for this reason, chloroginic acid. The cryssyropy consistence: three times their bulk of alcohol was added to them. The liquid
tallisable compound, or natural salt of coffee,
is a double chloroginate of potassa and caf. separated into two parts: one was viscid, and deposited ; the other was very fluid. The
feïne. If it be rubbed when it has just been latter, which contained the greater part of
dried at 212° F. on a warm sheet of paper, the new crystallisable compound, was de
it is electrified so as to adhere to the blade canted. It may be detected by putting a
of a knife presented to it, and so as to mainsmall quantity of the solution in a tube, and
tain the form of long, bulky flocks. adding a drop of ammonia: the yellow color,
When exposed to heat, it undergoes no verging on green, and that becoming gra
alteration up to 300° F.; but towards 365° dually more intense, is a certain indication of
F., it fuses, developes a beautiful yellow this fact; it led to the process about to be
color, boils, swells up to such an extent described, and also served as a guide in the
as to occupy five times its original space, ulterior operations, when, having mother
and remains spongy, yellowish, solid, and liquors to treat, it was necessary to eliminate
friable. When heated to 450° F., it becomes
brown; it is then partially decomposed. by means of alcohol foreign substances from the compound just obtained. To take from
The vapors which are disengaged from it the different precipitates a portion of the
give, in condensing, crystals of caffeïne in crystallisable compound, it is sufficient to
needles. If it be heated further, the brown dissolve them in a small quantity of water,
color becomes deeper, a fresh liquefaction then to precipitate it again by means of
takes place, abundant alkaline vapors are alcohol of 0.85 or 0.90 ; the supernatant
exhaled, the mass swells up again, so as liquor removes from the solution the sub
to assume four times its bulk, or twenty
times that of the crystals employed. stance sought.
The All the alcoholic solutions were distilled very light charcoal thus obtained has an on a sand bath. The syrupy residne was | Iridescent surface.* diluted with 0.25 of its bulk of alcohol at
| It is, doubtless, to the presence of the 0.90. Put into a cool place, it gave, after
Loftor chloroginate interposed in the cellulose of the 24 or 48 hours. grannlar crystals, which I perisperm that the swelling of coffee berries were collected in a filter and purified with In roasting must be attributed. cold alcohol at 0.65; they were washed on
| This double salt is very slightly soluble in a filter with alcohol of 0.70 to 0.85.
| anhydrous alcohol, even with the aid of heat. They were then re-dissolved to saturation
Its saturated solution in alcohol of 95°, in alcohol of 0:6, the mixture being heated
made with the aid of heat, allows it to crysin the sand bath. Cooling gives abundant
tallige, by cooling, in prisms radiating from and almost pure crystals : these are prisms
common centres. Being more soluble in algrouped in spheroids by the re-union of one
cohol of 85°, its crystallisation from it on of their ends in a common centre. The
cooling is more abundant: the solubility inpurification is finished by re-dissolving in
creases with the dilution of the alcohol. alcohol and re-crystallising twice. Finally,
Pure water dissolves still more of it, and it is allowed to drain, and dried in vacuo at
this solution saturated with heat cools in the 230° F.*
form of a mass. The cold solution, evapo
rated 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.
Crystals of double chloroginate, gently 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 1 decigramme of under receivers, with shallow vessels of sul. salt in a tube 5 millimetres in diameter and phuric acid.
Om. 12 in length.
heated in contact with potassa, become of a ginic acid under the combined influences of vermillion or orange red; heated further, water, air, and ammonia. One gramme the mixture fuses, takes a yellow color, of the natural compound is dissolved in disengages abundant ammoniacal vapors, ten cubic centimetres of water; two or becomes brown, &c.
three drops of ammonia are added, and Heated with monohydrated sulphuric acid, it is placed in a flat capsule under a bell the natural salt of coffee developes an in- glass in which the air is very slowly retense violet color and a bronzy pellicle. newed. The yellow, green, and blueish Hydrochloric acid produces analogous phe green colors succeed in twenty-four hours; nomena ; under the influence of nitric acid then the mixture acquires a brown tint. A an orange red color is manifested.
little water is occasionally added to compenIn solutions of the double chloroginate, sate for evaporation. After twenty or thirty acetate of lead gives a floculent, pale green days the conversion is finished; it is eva. ish yellow. The tribasic acetate produces a porated to dryness, and a very deep brown precipitate of similar form, but of a pure residue is obtained, which, detached in scales, yellow color. Nitrate of silver, alone, does powdered, and treated with boiling anhydrous not produce any change, but, previously alcobol, first dissolves and then crystallises mixed with a very small quantity of am- the caffeïne by cooling. The alteration of monia, it gives a yellow color which in the double salt by heat, carried only far clines to brown; the liquor becomes turbid; enough to turn the swelled-up matter slightly a pellicle of reduced metallic silver very soon brown, also enables us to extract a considerappears on the surface, and gradually ex- | able portion of the caffeïne by means of tends to the sides of the vessel.
boiling anhydrous alcohol. The proximate analysis of the double sait may be performed by several processes: the | EXTRACTION AND PROPERTIES OF CHLOROpotassa is determined by incineration, and is
GINIC ACID. represented by 0:11 of carbonate, or by the
Chloroginate of lead, completely purified conversion of this salt into sulphate.
by washing with boiled distilled water, and The compound dissolved and treated by a decomposed by a current of sulphuretted hy. quantity of sulphuric acid equivalent to the drogen, gives a solution which, rapidly evapotassa, then evaporated in contact with porated, permits a confused crystallisation of powdered marble, gives sulphate of potassa chloroginic acid. mixed with an acid chloroginate of caffeïne. This acid, purified by small quantities of Alcohol removes this organic compound anhydrous alcohol, is white, soluble in anhywhose acid may be precipitated by subacetate drous alcohol, more soluble in dilute alcohol, of lead. The caffeïne is extracted from the very soluble in water, and difficultly crystalsupernatant liquor, by washing the residue lisable. Its aqueous solution, almost saturated with cold alcohol, and treating what remains at the boiling temperature, crystallises only with hot alcohol; the latter, on cooling, depo. very slowly in microscopic prisms radiating sits caffeïne in crystals.
from common centres, presenting, after 20 or The chloroginate of lead may also be ob. 30 days, numerous agglomerations of sphetained either by precipitating the alcoholic rules of one or two millimetres in diameter. solution of the normal salt with tribasic Chloroginic acid dissolved in water has a acetate of lead and washing the precipitate, very acid re-action; it powerfully reddens or by triturating the same salt, without heat, litmus paper; it is the active principle in the with an excess of protoxide of lead and water. different colorings noticed above in the In the latter case, the potassa left in the natural salt of coffee. Heated in a tube, it mixture renders the chloroginate of lead fuses, turns yellow, boils, and leaves a thin soluble, forming, doubtless, another double shining layer of charcoal; its vapor concompound; but the disunion of the parts denses into a brown liquid, which, rapidly may be effected by a current of carbonic acid beated, leaves a very thin iridescent layer of introduced into the filtered liquid. This charcoal. solution retains the potassa and caffeïne. The elementary analyses of chloroginic
The latter may be extracted by evaporating acid, of the double chloroginate of potassa to dryness, wasbing the residue with cold and caffeïne, and of chloroginate of lead, alcohol, then dissolving the caffeïne in boiling gave the following results :alcohol, which, after filtration, makes its
Chloroginic Acid. appearance, filling with its crossed needles
56.0 the entire height of the liquid.
5.6 A fourth means, which is much longer, of Oxygen ..........
38.4 extracting the caffeïne from the double salt, consists in producing an alteration of chloro
'Chloroginate of Potassa and Caffeine.' which precede und uccompany the acts of
Carbon ................ 50:74 nutrition : it guides our senses, and, how-
7.50 of influencing our selection in the presence Proximate Composition of the Double Chio. of many kinds of food. roginate.
M. Chevreul, in a special report, has Chloroginic acid ........ 63-5 shown how we should take account of the Potassa ................
75 aroma and taste of broth, and by what Caffeïne................ 29 0
means they may be developed.
It is among the volatile acids, the etheri. 100.0
form or alcoholic compounds, the difProximate Composition of Chloroginate of ferent substances carried away by the Lead.
ammoniacal and aqueous vapors, and still Chloroginic acid ........ 40:0 more generally in the essential oils, that the Oxide of lead .......... 60.0 more or less complex causes of odors reside,
| and, in particular, that of the aroma belong
100.0 ing to alimentary substances. Equivalent Weight of Chloroginate Acid. Coffee contains aromatic essences, which C14
....... 84 the fat oil obtained by the processes de. HS...
scribed above powerfully retains; the aroma......... 56 tic properties are modified by torrefaction,
however slight. 148
It was in this state that it was desirable, Equivalent Weight of Chloroginate of Lead. with the view of applications, to extract, Acid ...... ........ 148
| study, and weigh these odoriferous bodies. Oxide 2 Pb 0.
224 In the hope of attaining this object, and
availing myself of the skilful co-operation of
372 M. Poinsot, I made a great number of disUndoubtedly a greater number of analyses tillations of several commercial kinds of of the various compounds are required in coffee, roasted at different degrees, in glass order to establish definitively the composi- apparatus, fractioning the products; the tion and formulæ of chloroginic acid and of latter were condensed at several temperathe chloroginates ; but the following facts tures, from 194° F. to from 4 to 6 below will remain demonstrated, independently of the freezing point of water. any further verification :
The infusion obtained by means of warm 1. A portion only of caffeïne is in the free water poured on ground coffee, in the proporstate in coffee; it may be extracted directly, tion of one quart of water to 100 grammes of without heat, and very pure.
coffee, was put into the first flask of the ap2. Caffeïne fulfils a basic part in the com- paratus; after two hours' boiling it did not reposition of the natural double salt.
tain any agreeable odor; the first receiver, 3. The alterations of the organic acid, whose temperature was gradually raised by whether spontaneous or produced by an ele the condensation of the vapor from 77° F. vation of temperature, set caffeine at liberty, to 194° F., contained distilled water occuand leave, combined with the potassa, a pying 0:1 of the bulk of the infusion, brown acid, the product of the ultimate On this water, which was of a slightly yellow transformation.
color, floated a few drops of a concrete 4. The double salt pre-exists in the nor white essence ; this essence, like the rest of mal state in the perisperm of coffee berries. the distilled liquid, was almost entirely de
5. Among the curious properties of chlo- prived of the agreeable aroma, whose traces roginic acid, the remarkable power which it might be confounded with the odor depossesses of developing a very intense green / veloped by several animal matters altered by color adds interest to the discovery of the boiling. crystallisable compounds which its rapid and The second receiver, maintained at the variable transformations had hitherto caused temperature of 77° to 86° F., had received to be overlooked.
scarcely 0 01 of the bulk of the infusion in
the form of a liquid, which was distilled when AROMATIC ESSENCE OF COFFEE.
the temperature of the first receiver had been Among the properties which distinguish allowed to rise to 194° F. This liquid, on our aliments, one of the most important, which floated minute quantities of concrete the aroma which these substances exhale- essence, exhaled an agreeable aromatic performs a great part in the phenomena odor, resembling that of coffee itself, but so
intense that a few drops of this water were appeared to result from the alteration of the sufficient to communicate to a cupful of milk oil possessing the most agreeable aromatic or any inodorous liquid, the agreeable aroma odor. There remained in the water, agiof coffee.
tated with ether, an etherial solution of the The particles of concrete essence were not second essence, endowed with a very sweet the source of this aroma; for, isolated and aromatic odor ; its proportions, small in the washed, they did not appear to retain any : inferior qualities, but large iu Mocha coffee, thus, the aromatic matter was entirely soluble appear to constitute the principal differences in water,
between the commercial qualities. It may The third receiver, cooled several degrees easily be extracted by placing pieces of below the freezing point, condensed a few chloride of calcium in the first two receivers ; drops of water exhaling the mixed odor of the solution of the chloride raises the temcoffee and of the pyrogenous hydrocarbons; perature in these vessels as the vapor conthe latter odor existed especially in the denses in them. A third receiver, surmounted fourth receiver, equally cooled, but whose by a tube filled with chloride of calcium, sides had condensed only traces of moisture ; | cooled to 68° F., retains, with the saline the same empyreumatic odor predominated solution, almost all the aromatic essence even in the aeriform matters which issued which is extracted by means of ether. The from the fourth receiver. The presence of total weight of the essence thus obtained carburetted hydrogen in the gases was proved amounted at most to two ten-thousandths of by passing them into a tube with bulbs full the weight of the coffee, and this may be of concentrated sulphuric acid : this acid understood, since one drop of this oil diffused acquired a deep brown color, and a deposi over a room a strong odor of coffee. tion of carbonaceous matters took place when The variable qualities for a long time ob. the acid was diluted with water.
served in the coffees of commerce are owing The presence and proportions of the carbon chiefly, doubtless, to the varieties cultivated, in these gases may be determined by directing and to the habitual or accidental circumthem through a tube for elementary analysis stances of vegetation, such as exposure, soil, filled with binoxide of copper, and collecting locality, the care taken in cultivation, and the carbonic acid disengaged.
the atmospheric conditions. It would be The proportions of the very volatile empy | interesting to endeavor to determine the reumatic carburets with a disagreeable odor influences of these different causes on the increased more and more when the roasting qualities of the product. of the coffee had been carried from that I devoted attention to discovering the which corresponds to a loss in weight of principal differences between two commercial 018 to that which is equivalent to the loss varieties, concerning the origin of which I of 0-25 beyond.
could not bave the least doubt-Martinico It is evident that it is possible to isolate and Mocha coffees. the residue and the products of an infusion The first is ordinarily in large berries, of coffee, so as to retain, in a form reduced presenting a depressed face; some berries, to a bulk of too, the greater part of the rolled in ellipsoïds, proceeding from fruits aromatic principles. These latter are com- of which one of the ovules was absent. Some plex; two odoriserous essential oils may be berries, still more rare, have a slightly angular extracted from them. It is sufficient, for form, dependent on the presence and the mu. that purpose, to strongly agitate the distilled tual pressure of three ovules in the same fruit. water which contains them, with 0.20 of its Mocha coffee differs from the foregoing in bulk of ether; it is left to repose for a that its berries have a yellowish grey color; quarter of an hour, when the supernatant they are smaller, their forms more irregular, ethereal solution is removed with a pipette. very generally flattened on the side, which This operation is repeated four times, and is in contact with another berry in each of the evaporation of the ether leaves an orange- the fruits. Some berries only are rounded, colored oil, the very powerful odor of which because they are found, each separately partly resembles the aroma which prevails developed, in a fruit in which one of the ovules more or less in all varieties of coffee. Ten is wanting. grammes of the water distilled from Mocha Many characters distinguish Mocha coffee coffee gave one centigramme of this oil, taking from all others; the fatty matter, which is account of the waste during the evaporation rather more abundant, forms 13-hundredths of the ether, which waste may be determined of the total weight; I could separate only by dissolving this essence a second time in two parts having different points of fusion, ether, and weighing again after a second | difficult to determine. It retained more evaporation. This essential oil was for.ned | powerfully a portion of the aromatic essence, of two parts; one, less yolatile and less fluid, sweeter, and in greater quantity.
The fatty matter of Martinico coffee, ex
74-5 tracted by the same means and exhausted by Legumine, caseïn (glutine) ? boiling water, is brownerand less fluid ; it may Chloroginate of potassa and be separated into 4 parts, wbose melting points caffeïne .............. 3-5 to 5 . are, respectively, 41, 65, 122, and 194° F. Nitrogenous organism...... This last part resembles the wax of leaves. Free caffeïne ............
0.8 The presence of a waxy matter and the Concrete essential oil, inso.
0.001 green color of the berries might depend on luble in water .......... the period of gathering and the time at which | Aromatic essence, fluid, with the barking was performed. In removing a sweet odor, soluble in the pulp of the fruit when it is full of juice, water, and, less soluble, the perisperm being quite moist, must un- aromatic essence .......
0.002 dergo in the air certain re-actions to which | Mineral substances : potassa, oxygen gives rise: thus the chloroginate lime, magnesia, phosphoric, undergoes partially the green transformation, sulphuric and silicic acids, the fatty substances are altered, and the and traces of chlorine ....
6.697 essence, less abundantly secreted, may thus be altered and partly escape.
100.000 These hypotheses, which agree with the It would be very interesting to know the results of analysis, led to the idea that the special effects, in the animal economy of the quality of certain coffees might be improved well-characterised substances which enter by allowing them to come to a more com- into the composition of coffee, and are not plete degree of maturity before the decorti- | found in any of the matters proposed as a cation. Perhaps if a portion of the crop substitute for it—what is the action of was left to ripen and dry, a quality would caffeïne which is so little alterable, of the be obtained analogous to those mixtures double chloroginate with a bitter after taste, of Mocha coffee with green coffees-of so unstable in the presence of oxygen, and, which many people prefer the mixed aroma finally, of the aromatic essences? We hope to the more soft aroma of the pure Mocha. that our learned practitioners will enlighten This interesting subject, with observations us on this point. made in our colonies, might be concluded, But already they have taught us, and the in France, with analytical experiments. experience of every day confirms it, that
The influence of the period of gathering, coffee, differing from the powerful alcoholic and of a particular mode of decortication, drinks and narcotic vapors which intoxicate seems to me to be manifested also in the and stupify the senses, seems to unite all results of the preparation of a very peculiar that is agreeable in the sensations of both kind of coffee, called Yungas in Bolivia, orders, exciting the intellectual faculties. This sort is in regular bulky berries of a Supposing that the principal cause of the yellowish grey color. Under these appear- special effects of coffee does not reside in the ances, we see only a light envelope in agreeable, diffusible aroma, it cannot be which lies a perisperm of the same form i doubted, at least, that this property has the and similarly marked; but which, having greatest influence on the commercial value ; shrunk more considerably by desiccation, is for this value is fixed according to the much smaller than the berries of ordinary | greater or less power, and the sweetness of coffees. In order to obtain this kind of the aroma in each variety; now, if we were coffee, it is gathered and barked very long to admit for the ponderal quantity of the before maturity. It is a fancy coffee which essence only two-thirds of the price of coffee, the Bolivians prefer, doubtless from custom, we should attribute to the principal essential although it developes less of the soft aroma oil the enormous value of 10,000 francs which characterises Mocha and several varie- (£400) the kilogramme. ties generally esteemed.
In combining the different analytical results, it was found that coffee in the normal
INVESTIGATIONS CONCERNING state, presents as nearly as possible the
THE COMPOUND AMMONIAS.* following composition :
BY M. ADOLPHE WURTZ. Cellulose ............ver
PREPARATION AND PROPERTIES OF MEHygroscopic water ........
THYLAMIXE. Fatty substances ..........
10 to 13
The process by means of which I obtained Glucose, dextrine, vegetable
this base does not differ from that which acid undetermined ......
* Comptes Rendus, No. 7, August 13, Carried forward.. . 74.5 | 1849.