188 METHODS OF ANALYSIS [Chap. 



9 Method II. {By Polarization) — Tentative. 



REAGENT. 



Millon's reagent. — Dissolve metallic mercury in an equal weight of concentrated 

 nitric acid and dilute the solution with an equal volume of water. The freshly 

 prepared solution must be used. 



1 DETERMINATION. 



Weigh 15.97 grams of the flour into a 300 cc. flask and add 100 cc. of alcohol (sp. 

 gr. 0.90). Shake at 30 minute intervals for 3 hours and then let stand overnight. 

 Filter through a dry, folded filter and polarize in a 200 mm. tube. Precipitate the 

 proteins in 50 cc. of the filtrate by the addition of 5 cc. of Millon's reagent. Shake, 

 filter and polarize the filtrate in a 200 mm. tube. Multiply the reading in degrees 

 Ventzke by 1.1 to correct for the dilution and deduct the product from the first 

 reading. This difference multiplied by 0.2 gives the per cent of gliadin^ nitrogen. 



1 1 PROTEIN SOLUBLE IN 5 PER CENT POTASSIUM SULPHATE SOLUTION.— TENTATIVE. 



Weigh 6 grams of the flour into a 200 cc. flask and introduce exactly 100 cc. of 

 5% potassium sulphate solution. Shake at 30 minute intervals for 3 hours and 

 let stand overnight or, better still, agitate at moderate speed in a shaker for 3 hours, 

 let settle 30 minutes, filter and determine the nitrogen in 50 cc. of the filtrate as 

 directed in I, 18, 21 or 23. 



12 GLOBULIN AND ALBUMIN (EDESTIN AND LEUCOSIN) AND AMINO NITROGENS- 



TENTATIVE. 



Weigh 10 grams of the flour into a 500 cc. Erlenmeyer flask, add 250 cc. of 1% 

 sodium chlorid solution, stopper the flask and shake thoroughly. Let stand, with 

 occasional shaking, for 3 hours, filter through dry paper and evaporate 100 cc. of 

 the filtrate to a small volume in a Kjeldahl digestion flask with 5 cc. of concentrated 

 sulphuric acid. Add the remainder of the sulphuric acid and determine the nitro- 

 gen as directed in I, 18, 21 or 23. To a second 100 cc. of the filtrate add 5 cc. of 20% 

 phosphotungstic acid solution, shake thoroughly, allow to settle and filter by de- 

 cantation. Wash slightly with water, concentrate the filtrate with 5 cc. of sul- 

 phuric acid in a Kjeldahl flask and determine the nitrogen (amino) as directed in 

 I, 18, 21 or 23. Deduct the amino nitrogen from the nitrogen found in the first frac- 

 tion to obtain the nitrogen as globulin and albumin'. 



■13 GLUTENIN.— TENTATIVE. 



Deduct the sum of the potassium sulphate-soluble nitrogen, 1 1 , and the alcohol- 

 soluble nitrogen, 8, from the total nitrogen, 7, and multiply the difference by 5.7. 



14 COLD WATER-SOLUBLE EXTRACT.— TENTATIVE. 



Weigh 20 grams of the flour into a 500 cc. Erlenmeyer flask and add gradually 

 200 cc. of water at 10°C., shake vigorously when about 50 cc. of water have been 

 added and continue shaking during the addition of the remainder. Allow to stand 

 at 10°C. for 40 minutes, shaking occasionally. Filter through a large, dry, coarse 

 filter paper, returning the first runnings to the filter until a clear filtrate is obtained. 

 Pipette 20 cc. of the clear filtrate into a tared dish, evaporate to dryness on a steam 

 bath, and dry to constant weight in an oven at 100°C. for periods of 30 minutes. 



