14 
Colorado Experiment Station 
as the test or trial sample. Of course, samples may be taken by hand 
from open bags, bins, etc. 
Fig. 2.—The seed to be tested as to purity is spread out on a sheet of paper. (A 
knife and simple tripod lens are all the apparatus necessary to separate the 
seed into pure seed, weed seed and other crop seeds, and inert matter. 
The first step in making a purity test is to spread the trial sample 
on a flat white surface, preferably cardboard over wood (Fig. 2). 
The necessary apparatus consists of tripod lens* and a knife or for¬ 
ceps for separating weeds, broken seed and inert matter from the seed. 
If the trial sample is too large, it may be divided and re-divicled (Fig. 
3) until the desired amount is obtained. 
TABLE III.—THE APPROXIMATE AMOUNTS OF SEEDS TO TAKE FOR 
PURITY TESTS 
Alfalfa, red clover, sweet clover... 1-6 oz. ( 5 grams) 
Timothy, alsike clover, white clover.1-16 oz. ( 2 grams) 
Wheat, oats, barley, rye, buckwheat ..1 oz. (28 grams) 
Brome grass .1-10 oz. ( 3 grams) 
Bluegrass, red top, Bermuda grass.1-28 oz. ( 1 gram ) 
Accurate scales or balances are seldom accessible to the farmer 
and for the majority it will be necessary to roughly estimate the per¬ 
centage of foreign material. (In IT. S. D. A. Farmer’s Bulletin No. 
428, T. H. Hillman has described a simple weighing device which 
should give fairly accurate results.) 
In making a home purity test some knowledge of weed seeds is 
necessary. For the purpose of determining the unknown weed seeds, 
* Tripod, lens and forceps are obtainable at any drug store. 
