In the detection of adulterants but little chemical work is necessary, hence methods will only be given tor the estimation of the principal constituents of coffee.

Moisture. - Dry in a flat dish to constant weight and calculate the moisture as usual. Caffeine. - The method of estimating this alkaloid in tea (p. 889) may he employed.

1A meteod used for the separation of xylan from wood. 2Lintner and Dull, Chem. Ztg., 1891, 266.

3 Ann. d. Chem. u. Pharm., 14, 236.

4 Mittl. a. d. Pharm. Inst. u. Lab. f. angew. Chem., Erlangen. Heft 3,1-56. 6 Wien. Akad. Ber. (2 Abth.), 81, 1,032; Jahresb. d. Chem. 1880,1069.

Fat. - Extract 2 grams of the finely powdered coffee in Soxlet's apparatus, or in one of the various modifications of this apparatus, with anhydrous alcohol-free ether. Remove the other from the extract by distillation and weigh the residue. Estimate the caffeine in this residue and deduct. The caffeine will probably amount to a small fraction of a per cent.

The sample of whole coffee beans may be prepared for analysis by means of a file or rasp. Particles of iron in the raspings should be removed by means of a magnet.

Albuminoid nitrogen. - (See p. 890.)

Crude fiber.1 - A quantity (6 to 8 grams) of the finely ground material is weighed into a flask, and treated several times with very dilute caustic potash (0.2 per cent), in order to remove the greater part of the albuminoids, Boil several times with a somewhat stronger solution of caustic potash (1.25 per cent), and after total removal of the alkali boil repeatedly with acetic acid. The residue after thorough washing with water is dried at 105° C. and weighed.

Caffetannic acid. - Owing to the lack of a method for the estimation of caffetannic acid, the following was devised by Mr. W. H. Krug, of the Chemical Division, for this report:

Weigh out duplicates of 2 grams each. Add 10 cc. of water and digest for 36 hours. Then add 25 cc 90 per cent alcohol, and digest for 24 hours more. Filter, washing the residue on the filter with 90 per cent alcohol. The filtrate contains tannin, caffeine, and traces of coloring matter and fat.. Heat it to the boiling point and add a boiling concentrated solution of lead acetate. If this is carefully done a caffetan-nato of lead containing 49 per cent lead will be precipitated. As soon as the precipitate has become flocculent it is collected on a filter, washed with 90 per cent alcohol until the washings show no lead with ammonium sulphide, washed with ether to remove traces of fat, dried and weighed. The composition of the precipitate is Pb3 (C15 H15 O82). Therefore weight of precipitate: weight of caffetannic acid:: 1263.63: 652.

Total soluble and insoluble ash. - Refer to page 891 under the analy-sis of teas for methods of ash determinations.

The color of the ash should be noted. A red ash is indicative of the use of Venetian red or other iron compounds in coloring the sample.