XV] CEREAL FOODS 189 



GLUTEN. 



15 Bamihl Test. (Qualitative) — Tentative. 



Place a very small quantity (about 1.5 mg.) of the flour on a microscope slide, 

 add a drop of water, containing 0.2 gram of water-soluble eosin in 1 liter, and mix 

 by means of a cover-glass, holding the latter at first in such a manner that it is raised 

 slightly above the slide, and taking care that none of the flour escapes from beneath 

 it. Finally allow the cover-glass to rest on the slide and rub it back and forth 

 until the gluten has collected into rolls. The operation should be carried out on 

 a white paper so that the formation of gluten rolls can be noted. Wheat flour, or 

 other flours containing gluten, show by this treatment a copious amount of gluten, 

 which absorbs the eosin with avidity, assuming a carmine color. Rye and corn 

 flour yield only a trace of gluten, and buckwheat flour no appreciable amount. 

 The preparations are best examined with the naked eye, thus gaining an idea of 

 the amount of gluten present. If the flour is coarse, or contains a considerable amount 

 of bran elements, as is true of buckwheat flour and low-grade wheat flour, the test 

 should be made after bolting, as the bran particles and coarse lumps interfere with 

 the formation of gluten rolls. 



16 Quantitative Method. — Tentative. 



Weigh 25 grams of the flour into a cup or porcelain mortar, add sufficient tap water 

 (about 15 cc.) to form a firm dough ball and work into a dough with a spatula or 

 pestle, taking care that none of the material adheres to the utensil employed. Allow 

 the dough to stand in water at room temperature for an hour, then knead gently 

 in a stream of tap water until the starch and all soluble matters are removed. This 

 operation requires approximately 12 minutes and should be performed over bolting 

 cloth or a horsehair sieve. To determine if the gluten is starch-free let 1 or 2 drops 

 of the wash water, obtained by squeezing the gluten, fall into a beaker containing 

 perfectly clear water. If starch is present a cloudiness appears. Allow the gluten 

 thus obtained to stand in water for an hour, then press as dry as possible between 

 the hands, roll into a ball, place in a tared, flat-bottomed dish and weigh as moist 

 gluten. Transfer to an oven, dry to constant weight at 100°C. (about 24 hours), 

 cool and weigh as dry gluten. 



CHLORIN. 



17 Qualitative Test. (Chlorin-Bleached Flours) — Tentative. 



Extract 30 grams of the flour with gasoline and allow the latter to evaporate. 

 A small amount of oil remains. Heat a piece of copper wire in a colorless gas flame 

 until it is black and no longer colors the flame green. Dip the hot end of the wire 

 into the oil and again bring into the flame. If chlorin or bromin has been used as 

 a bleaching agent, a green or blue coloration is produced. 



18 Quantitative Method. {Added Chloriri in Chlorin-Bleached Flours) — Tentative. 



Weigh 20 grams of the flour into a flat-bottomed aluminium dish, 8-10 cm. in 

 diameter, and dry 5 hours in a boiling water or steam oven, transfer, with as little 

 exposure to the air as possible, to a continuous fat extractor, and extract for 16 hours 

 with anhydrous alcohol-free ether, which is also free from chlorin. Transfer the 

 ether extract to a nickel disl^ and add 25 cc. of a solution containing 25 grams of 

 sodium hydroxid and 15 grams of sodium nitrate per liter. Place the dish on a 

 steam bath, evaporate to dryness and ignite in a muflSe at a dull red heat until 



