EXERCISE 14. TESTS FOR ADULTERATIONS OF CONCENTRATES 



Examination for impurities: Separate samples of 100 grams of the feed 

 into three portions, coarse, medium and fine, by means of two sieves, 20- 

 and 80-mesh (or into two portions by means of 50-mesh sieve). Examine 

 carefully each part for foreign matter: hulls (oats, rice, barley, buckwheat), 

 grain screenings, whole weed seeds, elevator or mill sweepings, ground corn 

 cobs, sawdust, ground stone pits (olive, brazil nuts), ground peanut hulls, 

 ground coffee hulls, sand, etc. 



Examination for moldiness: 5 grtims of the ground sample are mixed 

 with distilled water, poured on a Petri dish (or a saucer) and kept at 80 to 100 

 degrees F. for 24 hours or more. Examine for colonies of molds or bacteria 

 with a magnifier and compare these with those found in the case of similar 

 feeds of known purity. 



Weed seeds in concentrates: Separate and count the weed seeds in (a) 10 

 grams and (b) 20 grams of the thoroughly mixed feed sample and calculate 

 the average of the two. Determine their number in one pound and one ton 

 of the feed (one pound Avoirdupois equals 453 grams). 



Identify as many of the weed seeds as possible by comparison with a 

 standard collection of weed seeds, and give the number of noxious weeds in 

 the sample. (A collection of 200 economic seeds is prepared for schools by 

 the Bureau of Plant Industry, U. S. Dept. of Agriculture). 



Sand and mineral impurities: Place a tablespoonful of the feed in a tum- 

 bler, fill this three-fourths full with water, stir vigorously and pour off care- 

 fully the turbid liquid; repeat this until the top liquid is clear. The sedi- 

 ment will consist of sand, calcium carbonate, gypsum, or other mineral im- 

 purities, most of which may be readily identified. The per cent present may 

 be determined approximately by drying and weighing the sediment, pro- 

 vided a definite amount of feed was weighed out, e. g., 20 grams. 



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