Page images

















MEMOIR ON COFFEE.* showed, with their nitrogeno us composition :

-1. A peripheric cuticle covering, in all BY M. PAYEN.

their folds, the surfaces of the perisperm. PAYSSÉ, Chenevis, Cadet de Vaux and Cadet 2. The spongy nitrogenous substances filling de Gassicourt, examined the composition of the epidermic cellules, and containing olei. coffee, without isolating any of its proximate form matters. 3. In the more internal principles; Runge discovered, and Robiquet cellules, analogous granular bodies, constudied, caffeïne, a crystallisable nitrogenous | taining fatty substances. 4. Lamelliform substance : Robiquet observed in coffee two membranes, injected with nitrogenous matfatty substances, one of which appeared to ters, in the intercellular meati. him analogous to the resios.

PROXIMATE ANALYSIS. A skilful German chemist, Rochleder, examined, in 1844, the fatty matters of coffee :

The coffee should first be reduced to a le extracted from it palmitic and oleic acids; | powder by means of a mill or a pestle and he showed that coffee does not contain resin ;

mortar; it is afterwards exhausted with ether and he noticed the presence of a nitrogenous

in a displacement and continuous distillation substance-legumine. The resisting tissue

apparatus. appeared to him to be formed of one of the

The ethereal solution gives, on approachligneous substances which I have made ing to dryness, a fatty matter, which may be known.

separated by washing with boiling water. Notwithstanding the efforts of the scientific The aqueous solutions, mixed, leavea brown men I have named. the chemical knowledge at. | or fawn colored residue, which, treuted with tached to this important product left much to anhydrous alcohol,* yields, after evaporation, be desired. I have endeavored to extend it. Ja crystalline deposit, which, washed twice ORGANOGRAPHIC EXAMINATION.

in cold alcobol, dissolved twice in boiling

alcohol and crystallised, gives caffeïne in The resisting mass, of a horny appearance, distinct, white, brilliant prisms. forming the perisperm or endosperm of these Pure caffeïne thus obtained for the first berries freed from their pericarp, presents time directly, is fusible by heat and volatile under the microscope a tissue of juxtaposed without residue ; its vapors, condensed, recellules, with thick sides indented with irre- produced crystals sublimed in colorless and gular cavities, communicating with one ano diaphonous prisms. It gave, in four analyses, ther by small openings.

numbers differing but little from the admitted The thick sides, disaggregated by sul composition. Its elementary composition and phuric acid in presence of iodine, acquired its equivalent weight, hitherto undetermined, the blue color which denotes cellulose, then would correspond to the following formula:formed a gummy solution indicating des. trine. The agglomerated organic corpus. * The portion of the aqueous extract cules, colored orange by these re-agents, which does not dissolve in anhydrous alcohol

contains a small quantity of a new crystal* Annales de Chimie et de Physique, lisable compound of legumine and another xxvi., 108.

I nitrogenous matter. Vol. I.- No 1., October, 1849.


C16 H10 N

[ocr errors]



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, syrupy consistence : three times their bulk

for this reason, chloroginic acid. The crysof alcohol was added to them. The liquid

tallisable compound, or natural salt of coffee, separated into two parts: one was viscid, and

is a double chloroginate of potassa and cafdeposited ; 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 3650 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 by means of alcohol foreign substances from

brown; it is then partially decomposed. 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 residue 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

chloroginate interposed in the cellulose of the 24 or 48 hours, granular crystals, which

| 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

anhydrous alcohol, even with the aid of heat. a filter with alcohol of 0.70 to 0.85. 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

tallise, by cooling, in prisms radiating from and almost pure crystals : these are prisms

common centres. Being more solable in algrouped in spheroids by the re-union of one

cobol 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. ammonia, must be used; the same water

Crystals of double chloroginate, gently 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 under receivers, with shallow vessels of sul- salt in a tube 5 millimetres in diameter and Tric 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 alcohol, first dissolves and then crystallises mixed with a very small quantity of am- the caffeïde by cooling. The alteration of monia, it gives a yellow color which in- | the double salt by heat, carried only for 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

EXTRACTION AND PROPERTIES OF CALORO. may be performed by several processes ; the potassa 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 eva. potassa, 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 Carbon ................ the entire height of the liquid.

Hydrogen ..............

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



« EelmineJätka »