168 



FOODS AND FOOD ADULTERANTS. 



as it contains so much alcohol and water as to dissolve some of the tan- 

 nin. The substance freed from ether should be extracted with boiling 

 water, and the extract made up to such dilution that 10 c. c. is equal to 

 about 10 c. c. of the thirtieth normal permanganate solution used. The 

 titration must be performed slowly to insure accuracy, the permanganate 

 being run in at a rate of not more than a drop in a second or three 

 in two seconds. The eye must become accustomed to the bleaching of 

 the indigo and select some one tint of yellow as the end of reaction. It 

 js then possible to obtain duplicates agreeing within .1 c. c. even on en- 

 tirely different tests, as the following figures show : 



The 



results may be calculated to oxygen consumed or to percentage 

 of quercitannic acid, which would not be strictly correct, 1 c. c. of - 



oU 



permanganate being equivalent to .0052 grams of quercitanuic acid. The 

 results obtained with cloves and allspice will be found under those 

 spices. 



Crude fiber. This is a merely relative determination, as the term 

 crude fiber designates nothing absolute beyond the fact that a cer- 

 tain amount of substance is insoluble in acid and alkali of certain 

 strength after treatment for a definite length of time at a definite tem- 

 perature. The conditions selected by us are, 2 grams of substance, 200 

 c. c. of 5 per cent, hydrochloric acid, steam bath two hours, raising the 

 liquid to a temperature of 90 to 95 C., fiilration on linen cloth, washing 

 back into beaker with 200 c. c. 5 per cent, sodic hydrate, steam bath two 

 hours, filtration on asbestos, washing with hot water, alcohol, and ether, 

 drying at 120 weighing, ignition and crude fiber from loss in weight. 

 This method agrees practically with that known as the Weende method, 

 and while furnishing results which are of some comparative value, 

 leaves much to be desired. The subject will probably be reviewed soon 

 by the Association of Official Agricultural Chemists of the United States- 



Nitrogen and albuminoids. The methods of determining nitrogen and 

 albuminoids have been discussed and described at length in Bulletin 

 No, 12 of this division. The details of the method of Kjeldahl, as given 

 by Dr. Jenkins, which is the most convenient, are as follows : 



Determination of nitrogen by the method of Kjeldahl. 



REAGEXTS AND APPARATUS. 



(1) Hydrochloric acid whose absolute strength has been determined, (a) by precipi- 

 tating with silver nitrate and weighing the silver chloride, (b) by sodium carbonate, 

 as described in Freseuius's Quantitative Analysis, second American edition, page 680, 



