METHODS OF COFFEE ANALYSES. 907 
dance of furfuraldehyde was obtained, which indicates the presence of 
some pentose yielding substance. By treatment of a considerable por- 
tion of the water-insoluble material with a 5 per cent solution of sodium 
hydroxide, and by precipitation of the extract thus obtained with alco- 
hol,! a gummy substance was obtained. This gum yielded mucic acid 
by oxidation with nitric acid, an indication of the presence of a galac- 
tose yielding carbohydrate; by distillation with hydrochloric acid iur- 
furaldehyde was also obtained, showing the presence of a pentose yield- 
ing 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. 
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. 
Dierbach® 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. 
Kornauth* states that in the ash of pure coffees the potash amounts 
to from 50 to 200 times the soda. 
According to Bernheimer,’ the products obtained on roasting coffees 
are palmitic acid, caffeine, catfeol, acetic acid, carbonic acid, hydrochinon, 
methylamine, pyrol, and acetone. Caffeol is an oil, of the formula 
C,H,,O,, 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. 
METHODS OF ANALYSIS. 
Tn the detection of adulterants but little chemical work is necessary, 
hence methods will only be given for the estimation of the principal 
constituents of coffee. 
Moisture.—Dry ina flat dish to constant weight and caleulate the moisture as 
usual. 
Caffeine.—The method of estimating this alkaloid in tea (p. 889) may be employed. 
‘A meteod used for the separation of xylan from wood. 
?Lintner and Diill, 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. 
© Wien. Akad, Ber. (2 Abth.), 81, 1,032; Jahresb. d., Chem, 1880, 1069. 
