54 BULLETIN" 824, U. S. DEPARTMENT OF AGRICULTURE. 
Table 32. — Xitrogen in stems picked from u closed" flowers (Chrysanthemum cinera- 
rixfolium). 
Sample No. 
Xitrogen, 
N. 
Sample No. 
Xitrogen, 
X. 
14921 
Per cent. 
1.60 1 
1.40 
1.52 1 
1.54 1 
1.54 1 
1.77 ; 
1.21 
1.54 
17749 
Per cent. 
1.52 
14934 
17750 
17821 
18008 
Minimum 
Maximum 
Average 
1.52 
15009 
1.57 
15136 
1.63 
17389 
17394 
1 21 
17395 
1.77 
17621 
1 53 
It was found that a determination of the nitrogen and of the phos- 
phorus, together with a qualitative ether-extract test (to determine 
its color), were sufficient to determine the presence and approximate 
percentage of stems. 
In but few of the published analyses of insect powder, where ether 
extract is given as one of the determinations, is the kind of ether 
specified. In some methods the powder is simply shaken up with 
ether, filtered, and an aliquot evaporated. Dietze (70) has shown 
that the results do not agree when ether of specific gravity 0.720 
and of 0.735 is used. Ordinary ether contains some alcohol and 
water and extracts from insect-powder material other than the active 
insecticidal constituents. For concordant results, the ether used in 
making the extractions must always be of the same grade. Anhy- 
drous, alcohol-free ether would seem to be the best solvent to use. 
Pyrethrum flowers usually yield an intensely yellow ether extract, 
whereas the stems give one of a strong green color. The odor of the 
extract from the flowers is also characteristic. In the examination of 
commercial insect powder the presence of a material amount of 
powdered stems can always be detected by the green color of the 
ether extract. Its quantitative estimation is, however, of little value 
in determining the amount of stems present, and this determination 
was made in only a few cases, the method employed being as follows: 
The 2 grams used in the determination of moisture were transferred 
to an extraction thimble and extracted in a suitable apparatus for 
16 hours with ether that had been freshly distilled over metallic 
sodium. After extraction, the ethereal solution was evaporated to 
dryness on the steam bath and dried to constant weight at the temper- 
ature of boiling water. 
The petroleum-ether extract was determined in a few cases by 
thoroughly extracting 2 grams of the powder in a Soxhlet apparatus 
with commercial petroleum ether (specific gravity, 0.640; boiling 
point, 30° to 65° C), evaporating the extract on the steam bath, and 
drying for a few minutes in an oven at 100° C. 
