176 COFFEE 



adds and other substances. He states that chlorogenic acid, 

 C32H38O19, can be purified through its calcium salt and crystallized 

 as needles with melting point at 208 °C. It acts as a dibasic acid; 

 and, on hydrolysis with an alkali hydroxide, it yields caffeic or 3 : 4 

 dihydroxycinnamic and quinic acids. Chlorogenic acid gives a charac- 

 teristic color reaction by means of which its presence has been detected 

 in other seeds. Caffalic acid, C34H54O15, is obtained in the form of 

 prisms melting at 255 °C. and possessing a sweet taste. Caffeine seems 

 to exist in the seeds of Coffea liberica Bull in the form of potassium 

 caffeine chlorogenate, C32H360i9K2(C8Hio02N4)2.2H20. Gorter 

 isolated it in colorless prisms. He states that the fact that caffeine 

 can not be completely removed from cofiee with anhydrous organic 

 solvents is due to this association of caffeine with chlorogenic acid. 

 Contrary to this, Lendrich and Nottbohn maintain that the retention 

 of caffeine is due to adsorption by the tissue of the coffee-bean. 

 According to Allen and lately repeated an4 confirmed by the 

 author, it was noted that caffetannic acid, when it is dissolved in 

 ammonia water and the solution exposed to the air, produces a 

 bluish-green liquid owing to the formation of the oxidation-product, 

 viridic or viridinic acid, which is an amorphous brown substance, very 

 soluble in water and forms a solution which is turned green by 

 alkalies. It also gives a bluish-green precipitate with barium hy- 

 droxide solution; and a blue precipitate with lead acetate. Nestler 

 has used the production of this green coloration resulting from the 

 addition of alkalies to detect the presence of coffee in mixtures and 

 extracts. 



The determination of the sugar content of coffee has been care- 

 fully studied by Ewell, who found 6% of sucrose in fat-free coffee, 

 extracted by 70% alcohol. The insoluble matter after the com- 

 pletion of acid hydrolysis gives galactose. By distillation with hy- 

 drochloric acid, he obtained furfural equivalent to 90% of pentose. 

 He has obtained a gummy substance which on hydrolysis gave rise 

 to a reducing sugar, furfural; and mucic acid resulted on oxidation. 

 Therefore, Ewell concluded that the gummy substance was a com- 

 pound of pentose and galactose. Schultze and Maxwell found that 

 raw coffee contained galactan, mannan, and pentosans, the latter 

 present to the extent of 5% in raw and 3% in roasted coffee. Baker 

 states that manno-arabinose or manno-xylose forms one of the im- 



