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A

MONTHLY JOURNAL

OF

CHEMICAL PHILOSOPHY,

AND OF

CHEMISTRY APPLIED TO THE ARTS,
MANUFACTURES, AGRICULTURE, AND MEDICINE,

AND

RECORD OF PHARMACY.

EDITED BY

JOHN AND CHARLES WATT.

VOLUME I.-NEW SERIES.

LONDON:

W. AND T. PIPER, 23, PATERNOSTER ROW.

1849-50.

LONDON.

PRINTED BY R. BORN, CRAWLEY STREET, EUSTON SQUARE.

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 oleïc 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.

391135

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