The caffetannic acid of coffee has been isolated by Pfaff8 and by Rochleder.9 The latter chemist also reported the presence of traces of citric acid. Caffetannic acid as isolated by W. H. Krug in connection with this Department's investigations agrees with the description given by Beilstein.10 It is a light yellow, sticky mass, with a slightly acid and astringent taste. According to IIlasiwetz11 it is a yellow bitter mass of the formula C15h18O8.

Boussingault12 found in a sample of coffee 2.21 per cent mannite,8.73 per cent invert sugar, and 2.37 pet cent sucrose.

The carbohydrates of the coffee berry have received very little thorough study until quite recently. The recent investigations and discoveries in this line by Dr. Schulze at Zurich, and Dr. Tollens at Gottingen, and their collaborators, have brought about a more careful study of the carbohydrates of coffee among a host of other vegetable materials. Thanks to their labors, the percentages of compounds included in the term "other non-nitrogenous substances" have already been materially lessened in a great many cases.

1 Ann. Chem. Pharm., 1, 17.

2 Arch d.Pharm. [3 R.], 23, 684; Ztschr. anal. Chem. 25, 565.

3 Pol. Notizblatter, 1873, 257; Ztschr. anal. Chem. 1873, 442.

4 Chem. Centrbl., 1861, 989; Ztschr. anal. Chem. 1, 229.

"Mittl. a. <1. Pharm. Inst. 11. Lab. f. angew. Chem., Erlangen, Heft, 3,1-56.

6 Pflanzenstoffe, p. 1367.

7 Wien. Akad. Ber., 24, 40.

8Schweigg. Journ., 62, 31.

9 Wien. Acad. Ber., 7, 815.

l0Organische Chemie, Beilstein, 3, 343.

11 Hlasiwetz, Ann. Chem. Pharm., 149, 219.

12Compt. rend., 91, 639.

Rather indefinite statements about sugar, gum, and dextrin, make up the existing literature of the carbohydrates of coffee which are soluble in water. The coffee berry contains no starch. Mr. Walter Maxwell1 has demonstrated the presence of an insoluble carbohydrate which yields galactose by hydrolysis, and has succeeded in obtaining a considerable portion of very pure and well crystallized galactose. R. Reiss2 has reported mannose as an hydrolysis product of an insoluble carbohydrate of coffee.

By investigations made in this laboratory, cane sugar has been shown to be the principal soluble carbohydrate present. It is accompanied by a small percentage of a substance closely resembling dextrin and some reducing sugar. The latter may be due to the inversion of a small amount of the cane sugar before or during the process of extraction. A considerable amount of cane sugar was obtained in pure, well-defined crystals. For the purpose of isolating it from other soluble substances of the berry, the extract obtained by the use of 60 to 70 per cent alcohol is treated with a slight excess of lead acetate and the excess of the latter removed from the filtrate by means of hydrogen sulphide. The sugar is now converted into strontium saccharate by treatment with strontium hydroxide at the boiling point of the liquid. The precipitate of saccharate is separated by filtration, suspended in water, and decomposed by a current of carbon dioxide. The filtrate from the strontium carbonate thus formed is evaporated to a heavy sirup. This sirup is purified by repeated solution in alcohol, reevaporation and resolution, gradually increasing the strength of the alcohol. The final solution in very strong alcohol is left to crystalize. For this method we are indebted to Schulze, Steiger, and Maxwell.3

Just as satisfactory a preparation of cane sugar was obtained by the evaporation of the filtrate from the precipitated lead sulphide and by direct treatment of the residue with alcohol without the use of stron tium hydroxide. A preparation is now in progress without the use of either strontium hydroxide or lead acetate, and promises very good results, the separation being made by use of alcohol alone.

The portion of coffee insoluble in water is also being made the subject of detailed study. By distillation with hydrochloric acid an abun1 Unpublished notes. 2 Ber. d. d. chem. Gesell.. 1889, 22. G09. dance of furfuraldehyde was obtained, which indicates the presence of some pentose yielding substance. By treatment of a considerable portion of the water-insoluble material with a 5 per cent solution of sodium hydroxide, and by precipitation of the extract thus obtained with alcohol,1 a gummy substance was obtained. This gum yielded mucic acid by oxidation with nitric acid, an indication of the presence of a galactose yielding carbohydrate; by distillation with hydrochloric acid iur-fnraldehyde was also obtained, showing the presence of a pentose yielding substance in the gum. A galactose and pentose yielding gum has been separated from barley.2 Whether the gum obtained from coffee is a mixture of galactose and pentose yielding substances, or is a single substance yielding both, has not been determined.

3 Untersuchung iiber die chemische Znsammensetzung einige Leguminosensamen Laiulwirt, Versuchs-Stat., 1891. 39, 269.

The residue obtained by evaporation of the sulphuric acid extract of the insoluble material yields an abundance of mucic acid when oxydized with nitric acid, showing the presence of galactose, as stated by Maxwell.

Satisfactory evidence of the presence of any considerable amount of mannose in the sample of coffee used in the investigation has not yet been obtained. Parallel experiments with coffee and vegetable ivory dust were made. With the latter, an abundant precipitate of mannose hydrazon was obtained; with coffee, the precipitate was not of suffi cient amount for a satisfactory determination of its properties.

Dierbach3 isolated the coloring matter of coffee and termed it "coffee-green."

Coffee also contains traces of volatile oils and about 4 per cent of mineral matter. Potassium salts form a considerable proportion of the mineral matter. Silica, when present, amounts to little more than a trace.

Kornauth4 states that in the ash of pure coffees the potash amounts to from 50 to 200 times the soda.

According to Bernheimer,5 the products obtained on roasting coffees are palmitic acid, caffeine, caffeol, acetic acid, carbonic acid, hydrochinon, methylamine, pyrol, and acetone. Caffeol is an oil, of the formula C2H1002, boiling at a temperature of from 195° to 197° C.

A large number of analyses of coffees have been made, references to which are given in the bibliography accompanying this report.