906 FOODS AND FOOD ADULTERANTS. 



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 in- 

 cluded in the term "other non-nitrogenous substances" have already 

 been materially lessened in a great many cases. 



Rather indefinite statements about sugar, gum, and dextrin, make 

 up the existing literature of the carbohydrates of coftee which are 

 soluble in water. The coffee berry contains no starch. Mr. Walter 

 Maxwell 1 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. 

 Iteiss 2 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 de- 

 composed by a current of carbon dioxide. The filtrate from the stron- 

 tium carbonate thus formed is evaporated to a heavy sirup. This sirup 

 is purified by repeated solution in alcohol, ree'vaporation and resolu- 

 tion, gradually increasing the strength of the alcohol. The final solu- 

 tion 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 str<m 

 tium hydroxide. A preparation is now in progress without the use of 

 either strontium hydroxide or lead acetate, and promises .very good re- 

 sults, the separation being made by use of alcohol alone. 



The portion of coffee insoluble in water is also being made the sub- 

 ject of detailed study. By distillation with hydrochloric acid an abun 



1 Unpublished notes. 

 *Ber. <1. a. chem. Gvsell.. 1889, 22. 609. 

 3 Untersnchunjj iiber tlie cho.inisrhi' /iisammi-nsct/iinjj 

 Laiulwirt, Verauchs-Stat., 1891, 39, 269. 



