XXVI] COFFEES 333 



'Ig CRUDE FIBER.— TENTATIVE. 



Proceed as directed under VIII, 68. 

 IJ STARCH.-TENTATIVE. 



Extract 5 grams of the finely pulverized sample on a hardened filter with 5 suc- 

 cessive portions (10 cc. each) of ether; wash with smalljportions^of 95% alcohol 

 by volume until a total of 200 cc. have passed through, place the residue in a 

 beaker and proceed as directed under VIII, 62. 



1 8 SUGARS.— TENTATIVE. 

 Proceed as directed under VIII, 58 and 59. 



19 PETROLEUM ETHER EXTRACT.-TENTATIVE. 



Dry 2 grams of the coffee at 100°C., extract with petroleum ether (b. p. 35°-50°C.) 

 for 16 hours, evaporate the solvent, dry the residue at 100°C. and weigh. 



20 TOTAL ACIDITY.-TENTATIVE. 



Treat 10 grams of the sample, prepared as directed under 4, 'with 75 cc. of 80% 

 alcohol by volume in an Erlenmeyer flask, stopper and allow to stand 16 hours, 

 shaking occasionally. Filter and transfer an aliquot of the filtrate (25 cc. in the 

 case of green coffee, 10 cc. in the case of roasted coffee) to a beaker, dilute to about 

 100 cc. with water and titrate with N/10 alkali, using phenolphthalein as an indi- 

 cator. Express the result as the number of cc. of N/10 alkali required^to neutralize 

 the acidity of 100 grams of the sample. 



21 VOLATILE ACIDITY.-TENTATIVE. 



Into a volatile acid apparatus [XVI, 27; Fig. 8] introduce a few glass beads and 

 over these place 20 grams of the unground sample. Add 100 cc. of recentlj' boiled 

 water to the sample, place a sufficient quantity of recently boiled water in the outer 

 flask and distil until the distillate is no longer acid to litmus paper (usually 100 cc. 

 of distillate will be collected). Titrate the distillate with N/10 alkali, using phenol- 

 phthalein as an indicator. Express the result as the number of cc. of N/10 alkali 

 required to neutralize the acidity of 100 grams of the sample. 



COATING AND GLAZING SUBSTANCES. 



22 SUGAR AND DEXTRIN.— TENTATIVE. 



Introduce 100 grams of the whole coffee into a beaker, add exactly 300 cc. of 

 water, stir and allow to stand 5 minutes, with frequent stirring. Filter through a 

 dry paper, add carefully to the filtrate sufficient dry lead acetate to precipitate 

 all the caffetannic acid, avoiding an excess. Filter through dry paper and re- 

 move the lead from the filtrate by the addition of a slight excess of anhydrous 

 potassium oxalate. Filter through a dry paper and determine reducing sugars as 

 invert sugar in 50 cc. of the filtrate, as directed in VIII, 25. Invert a 75 cc. aliquot 

 of the filtrate as directed under VIII, 14. Cool, nearly neutralize with sodium 

 hydroxid solution, make up to 100 cc. and determine reducing sugars as invert sugar 

 in the resulting solution, as directed under VIII, 25. Measure a 100 cc. aliquot 

 of the filtrate into a 200 cc. flask, add 10 cc. of 25% hydrochloric acid and hy- 

 drolyze as directed under VlII, 60. Cool, neutralize with sodium hydroxid solu- 

 tion, make up to volume, filter through a dry paper and determine reducing sugars 

 as invert sugar in 50 cc. of the filtrate as directed under VIII, 25. Calculate the 



