2 BULLETIN 839, U. S. DEPARTMENT OF AGRICULTURE. 



parison. As a rule, not less than 12 microscopical mounts were 

 made of the standard and of the sample under examination. 



Kohn (10) weighed out one-half gram of the flour, and added 10 

 cubic centimeters of ether, shaking the mixture, to isolate the hairs 

 and bran tissues which were subsequently identified under the 

 microscope. 



Dedrick (4) placed the flour in question upon a glass, and exam- 

 ined it for offal particles, either with the naked eye or by means of a 

 powerful magnifier. Particles of bran, germ, or other impurities 

 or substances differing from flour were enumerated, five and six 

 trials being made and an average struck. In this way he attempted 

 to differentiate between the so-called patent, straight, clear, break, 

 and low-grade flours. 



Collin (3) considered the microscopical examination of flour quite 

 extensively, although he did not take up the question from the stand- 

 point of determining the relative amount of offal material present. 

 The histology of the wheat grain is fully discussed and illustrated 

 with a number of figures. 



Von Liebermann and Andriska (22) suggested a method for esti- 

 mating the quality of wheat flour which might possibly be correlated 

 with a microscopical examination. The quality of the flour with 

 respect to the quantity of bran substance present was ascertained 

 by shaking the flour with chloroform, and observing the color of 

 the portion which floated on the surface. The test might be rendered 

 quantitative in the following manner: One gram of the flour was 

 shaken in a tube with 10 cubic centimeters of chloroform, and the 

 mixture allowed to stand for one hour. The depth of color of the 

 layer which then formed on the surface of the chloroform was com- 

 pared with the colors of the layers produced when mixtures of finest 

 white flours and variable portions of bran were subjected to similar 

 treatment. These mixtures might contain quantities of washed bran 

 ranging from to 2 per cent. The colors of the layers were to be 

 observed from above. 



In connection with the work done by Moore and Wilson (15), Pat- 

 terson has made a microscopical examination of the flour streams 

 from the different machines of the mill, these streams being blended 

 to form various finished flours. Finished flours were also examined. 

 His method consisted in weighing out 3 milligrams (0.003 gram) of 

 flour, dividing this into five portions on as many microscopic slides, 

 wetting with water, covering with cover slips, and then counting 

 under the microscope the number of hairs and epicarp and seed- 

 coat particles in the five slides. His results tended to show how 

 these particles increased in number in streams from the lower-grade 

 machines and were practically absent from those from the "top" 

 of the mill. 



