38 



BULLETIN 102, U. S. DEPARTMENT OF AGRICULTURE. 



of a mechanical analysis. Directed only by his judgment in a mechan- 

 ical separation of "damaged kernels" from "sound kernels" in any 

 given sample, the analyst is entirely without means of expressing in 

 any standard way the quality and soundness of the sample as a 

 whole. He is, furthermore, entirely without means of confirming 

 his judgment or opinion in his discrimination between sound and 

 damaged kernels by any standard test or criterion. 



The results of these corn-acidity investigations indicate that the acid 

 test is such a criterion, and it is offered as an aid to any analyst or 

 inspector who desires to determine in a uniform, standard, and scien- 

 tific way the quality and soundness of corn. 



In order to classify corn as to quality and soundness by means of 

 the acid test, it is necessary to fix certain limits in the degree of 

 acidity, above which limits the corn may be said to be unsound as 

 compared to corn below such limits. It is only in a general, broad 

 way that these limits are suggested. Corn which is to the eye 

 unquestionably of poor quality and unsound shows invariably a high 

 degree of acidity between limits of 30 and 50 c. c. Corn showing 

 above 50 c. c. in degree of acidity is in a very advanced stage of 

 deterioration, and its quality does not need to be tested in any other 

 way than by inspection. 



As a result of these and other investigations of the acidity of corn 

 in this country 1 and abroad, a limit of 30 c. c. seems most appro- 

 priate in discriminating against wholly bad or unsound corn. Any 

 corn with a degree of acidity more than 30 c. c. is unquestionably 

 unsound and of very poor quality. 



Of samples representing approximately 2,450 cars of corn received 

 at a principal terminal market from December, 1911, to May, 1913, 

 inclusive, 87 were found to have a degree of acidity greater than 

 30 c. c. The results of analyses, together with the commercial grade 

 and the remarks of the inspector who graded the samples, are shown 

 in Table XIX. 



Table XIX. — Quality and condition of corn which showed a degree of acidity greater 

 than 30 c. c, as found in representative samples at a principal terminal market. 



Labo- 

 ratory 

 No. 



Month. 



Grade. 



Mois- 

 ture. 



Cob 

 rot. 



Heat 

 dam- 

 aged. 



Ger- 

 mina- 

 tion. 



Acid- 

 itv. 



Inspector's remarks; 



:'„si% 

 38665 

 38498 

 38520 

 38531 

 38572 

 38619 

 38748 

 38495 



July. 



.do.... 

 .do.... 

 .do.... 

 .do.... 



.do 



.do 



.do 



.do 



3 



3 



Sample 

 ..do... 

 ..do... 

 ..do... 

 ..do... 

 ..do... 

 4 



Per 

 cent. 

 13.0 

 14.7 

 15.2 

 15.7 

 14.6 

 14.6 

 14.8 

 14.4 

 14.0 



Per 

 cent. 



4.00 

 22.60 







11.00 

 22. 25 



1.85 

 15.85 

 44. 00 

 15. 65 



Per 

 cent. 









 15. 10 











5.70 















Per 

 cent. 



2 



4 37. 6 Subject; heating. 



6 33. Heating; one end hot. 



2 35. 7 Heating. 



33.4 Slightly heating. 



32. 8 Heating. 



41.5 Do. 



38.7 Subject; too much damage for 3. 



1 Black, O. F., and Alsberg, C. L. The determination of the deterioration of maize, with incidental 

 reference to pellagra. U. S. Department of Agriculture, Bureau of Plant Industry Bulletin 199. 36 p., 1910. 



2 Explanation of terms: Subject=grade subject to change upon ^inspection; mahogany-^badly heat 



Too much damage. 



