In preparing the tables on the following pages, showing the composition of Coffees, the better known authorities have been consulted and analyses have been selected which give the principal constituents of the grades usually found in our markets.

The estimation of the sucrose in sample No. 8712 was accidentally omitted. Judging from other analyses made in the Division of Chemistry the average per cent sugars given by Konig is rather high. Considerable quantities of pure sucrose have been separated from coffees in the course of these investigations. It has been definitely determined that the soluble carbohydrates of coffee consist very largely of sucrose.

The caffetannic acid in No. 8712 was estimated by a method described on page 908. Many of the statements in regard to this constituent are very indefinite; no description of the methods for its estimation could be found in the literature accessible.

1 Dictionary of Applied Chemistry, p. 578.

Table Showing The Chemical Composition Of Unroasted Coffees

1 From Zusammensetzung der menschlichen Nabrungs-und Genussmittel, J. Konig, p. 1001. 2 Loc. cit. 3 Includes caramel. gum, tannin, etc.

4 Food, Its Adulterations and Methods for its Detection, A. H. Hassall, p. 146.

5 Includes cellulose and insoluble coloring matter.

6 Nitrogen, free extract matter.

7 Konig op. cit., p. 1002.

The Chemical Composition Of Roasted Coffees

1 Reported as cane sugar.

2 Hassall, of cit., 146.

3 Foods, their composition and analysis, A. W. Blyth, 346.

4 Konig, of cit, 1002.

5 Loc. cit.

Composition Of Some Pure Coffees

[A. Smetham, Analyst, 1882.73.1

No. 1, Ceylon coffee; No. 2, Costa Rica; No. 3, Ceylon; No. 4, East Indian coffee; No. 5, Jamaica; Nos. 6 and 7, best and purest kinds of coffee bought from a wholesale dealer.

Analyses Of Various Coffees [O. Levesie, Arch. Pharm. (3) 8 294.]

No. 1, best Jamaica; No. 2, best green Mocha; No. 3, pearl Ceylon; No. 4, washed Rio; No. 5, Costa. Rica; No. 6, Malabar; No. 7, East Indian coffee.

The Ash Of Coffees*

* The descriptions of samples are based on the dealer's statements.

+ Numbers given are parts in 100 of mineral matter after deduction of carbon dioxide. Oxygen equivalent to chlorine is not deducted. Soluble in solution of sodium carbonate.

One of the most important constituents of coffee is the alkaloid caffeine. This alkaloid is identical, chemically and physiologically, with that present in tea and termed "theine." Coffee contains a much smaller proportion of this alkaloid than is found in tea leaves. Caffeine was discovered in 1820 by Runge,1 and was isolated some time afterwards by Pelletier,2 Robiquet,3 Caventon, and Garrot. This alkaloid is also found in the leaves of the coffee tree. According to Payen4 caffeine is present as a caffetannate. Caffeine may readily be obtained from coffee by extraction with chloroform. The alkaloid separated in this way, after purification, is obtained on evaporating the solvent in beautiful white silky, fibrous crystals. Unroasted coffees contain from a little less than 1 per cent to approximately 2 per cent of caffeine. Payen5 reports from 3.5 to 5 per cent caffeine plus caffetannate of potassium, the free alkaloid amounting to .8 per cent. Caffeine6 melts at 224° to 228° C, sublimes at 187° C, is soluble in 58 parts of Water at 20° C, in 9.5 parts of water at 100° C, in 21 parts alcohol, in 545 parts of ether and in 9 parts of chloroform at 20° C. According to Lapean7 the solubility of caffeine in alcohol at 15.5° 0. is 1 part in 150 of the solvent. "Blyth cautions the analyst against drying this alkaloid at 100° C. as is usual, and claims that it commences to sublime at 79° 0. The specific gravity' of caffeine at 10° C. is 1.23. The following reactions are given by Luchini:2 Wenzell's reagent (solution of 1 part KMn04 in 200 parts of hot H2S04), gives an amethyst color with caffeine, which changes to a dark violet, then becomes blood red and after twenty-four hours a brown precipitate forms: 1 part caffeine in 10,000 can be detected by this reagent. With Luchini's reagent (a hot solution of K2Cr2O7 in concentrated H2S04 there is no change on standing twenty-four hours. According to Bottiger3 caffeine may be detected by evaporating an alcoholic extract of the substance to dryness, treating with hydrochloric acid, again drying, then adding water. The presence of the alkaloid is shown by a purple-red color. Schwar-zenbach4 employs chlorine water instead of hydrochloric acid in the above test. The purple residue becomes yellow on heating and red when treated with ammonia.

1 Schweigg. Jour. Chem. Phys. 31, 308.

2Jour. Pharm. [2], 12, 229.

3 Op. eit., 234.

4Ann. chim. phys. [3] 16, 108; Jahresb. ii. d. Fortsch, <1. Chem. 1849, 486.

5Ann. chim. phys. [3] 26, 106; Jahresb. ii. <l. Forteeh. d. Ohem. 1849, 486.

6Vierteljahreschr. pr. Pharm 16, 167.

7 pharm. J. Trans. [3], 11, 902; Jahresb. d. Chem. 1881, 902.

8 Foods: Their composition and analysis. A. W. Blyth.

Kornauth5 evidently overestimates the percentage of caffeine in coffees. He states that a percentage of caffeine below 1.97 is an indication of an adulterated sample. The writer's analyses and those quoted in the table (p. 902) all show percentages of caffeine considerably below the limit given by Kornauth.

The fat is a prominent constituent of coffee. Husemann6 separated a white, odorless fat on cooling an alcoholic extract of coffee. The melting point of the fat was 37.5° C.; it consists7 of the glycerides of palmitic acid and of an acid (C12H24O2). The percentage of fat in raw coffee is approximately 13.