CONSTITUENTS OF COFFEES. 905 



loid at 100 C. as is usual, and claims tliat it commences to sublime at 

 79 C. The specific gravity ' of caffeine at 10 C. is 1.23. The follow- 

 ing reactions are given by Luchini: 2 Weuzell's reagent (solution of 1 

 part KMnO 4 in 200 parts of hot H 2 SO 4 ), 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 KsCr 2 O 7 in concentrated H.,SO 4 there is no change on 

 standing twenty-four hours. According to Bottiger 3 caffeine may be 

 detected by evaporating an alcoholic extract of the substance to dry- 

 ness, treating with hydrochloric acid, again drying, then adding water. 

 The presence of the alkaloid is shown by a purple-red color. Schwar- 

 zenbach 4 employs chlorine water instead of hydrochloric acid in the 

 above test. The purple residue becomes yellow on heating and red 

 when treated with ammonia. 



Kornauth 5 evidently overestimates the percentage of caffeine in 

 coffees. He states that a percentage of caffeine below 1.97 is an indi- 

 cation 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. Husemann 6 separated 

 a white, odorless fat on cooling an alcoholic extract of coffee. The 

 melting point of the fat was 37.5 0.; it consists 7 of the glycerides of 

 palmitic acid and of an acid (Ci 2 H 24 O 2 ). The percentage of fat in raw 

 coffee is approximately 13. 



The caffetannic acid of coffee has been isolated by Pfaff B and by 

 Kochleder. 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 Illasiwetz 11 it is a yellow bitter mass 

 of the formula Cj 5 II] 8 O 8 . 



Boussingault 12 found in a sample of coffee 2.21 per cent mannite,8.73 

 per cent invert sugar, and 2.37 per cent sucrose. 



The carbohydrates of the coffee berry have received very little 



1 Ann. Chem. Pharin., 1, 17. 



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



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

 <Chem. Centrhl., 1861, 989; Ztschr. anal. Chem. 1, 229. 



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

 fi Pflanzenstoffe, p. 1367. 

 7 Wien. Akad. 15er., 24, 10. 

 "Schweigg. Journ., 62, 31. 

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

 lo Organische Chemie, Beilstein, 3, 343. 

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

 12 Corapt. rend., 91, 639. 



