646 



SCIENCE 



[N. S. Vol. XLVII. No. 1226 



they contained. Various other tests have been 

 proposed for this purpose, and the most suc- 

 cessful may be summarized as follows : 

 (a) The percentage of ash. 

 (6) The relative proportion of fiber and debris, 



as suggested by Girard^ (1884), Buch- 



wald^ (1913), and others. 



(c) The content of pentosans, as indicated by 



Koning and Mooj= (1914). 



(d) The relative change in color resulting 



from the addition of water and subse- 

 quent exposure to the air, a procedure 

 making use of this color change having 

 been patented by Hein<= (1910). 



(e) The catalase activity, as developed by 



Wender and Lewin' (1904), MiUer^ 

 (1909), and others, and discussed in a 

 paper by the writer^ (1918). 

 (/) The comparative color of the dry flour, 

 particularly after compression on a slab, 

 the procedure being commonly known 

 as the Pekar test. 

 The percentage of acidity, and of the soluble 

 proteins and carbohydrates ordinarily dimin- 

 ishes with increasing refinement and "grade" 

 of wheat flour. There are many exceptions to 

 this rule, however, due to unsoundness of the 

 wheat, or decomposition of certain 'flour consti- 

 tuents subsequent to milling, which may re- 

 sult in increasing the percentage of one or all 

 of these groups of substances. The ash con- 

 tent is apparently more generally employed 

 for detecting the relative grade of wheat flour 

 than any other tests mentioned, with the pos- 

 sible exception of color. The latter is ob- 

 jectionable as a test because of the difficulty 

 of expressing the results numerically. "While 

 certain instruments have been suggested for 

 this purpose their use is not common. 



* Buchwald, J., Ztschr. ges. Getreidew, 5, 50, 

 1913. 



« Koning, C. J., and Mooj, W. C, Jr., Chem. 

 WeelcUaa, 11, 1064-66, 1914. 



6 Hein, G., German Patent 250,413, November 13, 

 1910. 



7 Wender, N., and Lewin, D., Oester. Chem. Z., 7, 

 173-175, 1904. 



8 Miller, M., Ztschr. ges. Getreidew., 1, 194r-200; 

 214-222; 238-244, 1909. 



» Bailey, C. H., Jour. Biol. Chem., 32, 539-545, 



The almost universal use of the ash content 

 in this connection suggested to the author that 

 variations in these mineral constituents might 

 be accompanied by corresponding variations in 

 the electrical conductivity of water extracts 

 of the flours. This could be postulated, if 

 Swanson's (1912) suggestion that the principal 

 inorganic elements of the ash, potassium and 

 phosphorus are present in part m the water 

 extract as potassium phosphate is correct. To 

 ascertain whether or not such a relation ex- 

 isted, a series of flour samples was collected 

 from a Minnesota flour mill, representing 

 each of the flour streams. There were five 

 break flours, three sizings flours, seven mid- 

 dlings flours, two tailings and three low-grade 

 flours, in addition to the patent, clear, and 

 red-dog flours marketed by the mill. These 

 were employed in the conductivity studies be- 

 cause they afforded a progressive series from 

 the standpoint of grade, with wide differences 

 between the extremes. With the assistance of 

 Miss Anna Peterson the effect of several va- 

 riations in the technique and method were 

 studied, and it was observed that the tem- 

 perature at which the extraction was con- 

 ducted was of greatest significance. The con- 

 ductivity of extracts maintained at 40° during 

 the period of extraction was materially greater 

 than that extracted at 0°. "With a certaia 

 flour these values for « X 10"* at 30° for ex- 

 tracts prepared at 40° and 0° were 4.83 and 

 6.00 respectively. The proportion of flour to 

 water in the mixture during extraction was of 

 importance, and a ratio of 1 part of flour to 

 10 parts of water was deemed most satisfactory. 

 The treatment of the extract must be uniform 

 and there was the least variation in the results 

 when the extract was clarified by eentrifuging 

 for a few minutes, followed by filtration of 

 the supernatant liquid. If the suspension of 

 flour in water was placed in the conductivity 

 cell without first filtering it, the conductivity 

 gradually increased as the flour particles set- 

 tled out of suspension. The period of ex- 

 traction was of less significance than was an- 

 ticipated, and 15 minutes' continuous shaking 

 in a thermostat at the desired temperature 



