334 METHODS OF ANALYSIS 



reducing sugars in each instance to per cent by weight of the original coffee. Cal- 

 culate sucrose from the reducing sugars before and after inversion as directed in 

 VIII, 18, and calculate dextrin as follows: Subtract the reducing sugars after in- 

 version from the reducing sugars after hydrolysis, multiply the difference by the 

 factor 0.9561 to convert the result to dextrose and then by 0.9 to convert to dextrin. 

 In some instances the presence of sucrose in the water extract may be verified 

 by polarization. The presence of dextrin in the water extract may be verified by 

 polarization as directed under IX, 25, and by the erythro-dextrin test [IX, 47] 

 performed on the water extract previous to clarification with lead acetate. 



23 EGG ALBUMEN AND GELATIN.— TENTATIVE. 



Treat 100 grams of the whole coffee with 500 cc. of water and allow to stand with 

 frequent stirring for 5 minutes. Filter and treat separate portions of the filtrate 

 with (1) a strong solution of tannic acid; (2) Millon's reagent [XV, 9]; (3) by 

 boiling. In the presence of egg albumen a more or less heavy precipitate will 

 be formed in each case. As a confirmatory test, treat an aliquot of the filtrate with 

 an excess of tannic acid solution, add a little salt if necessary to secure flocculation 

 of the precipitate, filter and, without washing, introduce the paper and its con- 

 tents into a Kjeldahl flask and determine nitrogen. By this method coffee not 

 coated with albumen or gelatin will yield less than 10 mg. of nitrogen per 100 grams 

 of sample. 



24 CHICORY INFUSION.-TENTATIVE, 



Cover 100-150 grams of the whole coffee with water, allow to soak 2-3 minutes, 

 stirring frequently, and drain the aqueous washings through a coarse sieve. Wash 

 the coffee upon the sieve with about 100 cc. of water and centrifugalize the com- 

 bined washings. Decant the clear liquid from the sediment, drain almost dry upon 

 filter paper, then mount the sediment in chloral hydrate [XXTV, 20 (f )] and exam- 

 ine under the microscope for elements of chicory. 



FATS AND WAXES, 



25 Spath Method^.— Tentative. 



Treat 100-200 grams of the beans with low boiling petroleum ether for 10 min- 

 utes, pour off the petroleum ether and repeat the process. Filter the combined 

 petroleum ether extracts, evaporate and determine the index of refraction and the 

 saponification number of the residue, as directed under XXIII, 6 and 20. 



BIBLIOGRAPHY. 

 lAnn., 1908, 358:327. 



2 Allen. Commercial Organic Analysis. 4th ed., 1909-14, 6: 607. 



3 Forschb. uber Lebensm., 1895, 2: 223. 



