217 



NTY 



that produced in the water extract of the sample in question, all of which can 

 di.- pe used with when the purpose is merely to learn whether or not the flour is 1 .1 

 ami whether the bleaching is light, moderate, or excessive. Then- has also been a 

 demand not only for a simple and rapid method for detecting bleaching in the 

 laboratory, but also tor one which flour buyers, bakers, and consumers can carry out 

 without special training ami with simple apparatus. 



The tests here described are, first, a simplification of the Griess-Ilosvay method and, 

 second, a confirmatory test based on the observations o Alway a and others that the 

 petroleum ether solution of unbleached flour is yellow, while that of bleached Hour, 

 if not excessively overbleached, is nearly colorless. The Griess-Ilosvay test is the 

 more reliable, but the gasoline test, which depends on an entirely different principle, 

 namely, the nature of the coloring matter of the fat, is useful for confirmation. A 

 description of the teet in popular language follows: 



I ' METHOD. 



Place a heaping teaspoonful (10 grains of the flour to be examined in a wide- 

 mouthed, glass-stoppered l-otince bottle. Nearly till with distilled water, or tap 

 water five from an appreciable amount of nitrites, and add a teaspoonful (-1 eo of the 

 t'-t ^olution prepared as .lirected In-low, measured with a glass spoon. Cork the 

 bottle and shake vigorously for a few minutes, then allow to settle for from fifteen to 

 twentv mil. 



Under the above conditions bleached flour will impart to the liquid a color ranging 

 from a liirht pink to a deep red, depending on the degree of bleaching. With un 

 bleached Hour the liquid i- nt colored a red tint, provided water free from nitrite* i- 

 used. Always run, for comparison, a parallel t-t with a -ample of unbleached (lour, 

 so that allowance can be made for any nitrites in the water. 



Test solution. 1. Dissolve 0.5gram of sulphanilic acid in 150 cc of dilute acet i. : ,cid 

 (about _'(> percenJ . Keep u.-n t-ppered. 



Dissolve 0.2 gram of alpha-naphthylamin bydrochktid in 20 cc of -iron- acetic 

 Doc of dilute acetic acid (20 per cent). Keep well stoppered. 

 I anl _' for use. The mfxed reagent keeps for several weeks, and possibly 

 much longer. 



II (.A HO LINK METHOD. 



Place two heaping teaspoonfuk (20 grams) of the flour in a wi<ic-inoiithe<l, ^lass- 

 stoppcred i-on:. . add sufficient gasoline to nearly till the bottle, .-hake. ; m I 



allou to -ettle If the flour is unbleached, the u r a.-oline will become distinctly yellow; 

 if bleached, it will remain nearly colorless. ',,nduci a parallel test on unbleached 

 Hour for comparison. 



A MODIFICATION OF THE BAMIHL TEST FOR DETECTING WHEAT 

 FLOUR IN RYE FLOUR. 



\ I. \\INTON. 



This test depends on the presence of gluten in wheat flour and its absence in con- 

 siderable amounts in rye and other flours. The original test, devised in 1852 by 

 Bamihl,b a Prussian customs official, consists in rubbing up a small amount of flour 

 with water on a microscopic slide by means of a cover glass and noting under the mi- 

 croscope whether or not gluten strings or rolls are formed. The objections to the test 

 in its original form are that the microscope reveals the presence of traces of gluten in 

 pure rye flour and under the microscope it is not possible to compare at a glance the 

 amount found in pure rye flour with that from a suspected sample. 



The writer's modification of the test consists in employing a dilute solution of eosin 

 in place of water and dispensing with the microscope entirely. The gluten greedily 



"braska Agr. Exp. Sta., Bui. 102. 

 & Poggendorff, Annalen Physik Chemie, 1852, 86; 161. 



