Circular 21 - Insecticides and Subsidiary Materials 63 
Petroleum in crude form may be bought 
at the wells for ^3 cents to :i?2.19 per barrel 
depending upon the location. 
Available on contract: see Class 1^, 
General Schedule of Supplies, Procurement 
Division, Treasury Departraent . 
PHOSPHORUS PASTE 
Phosphorus paste is useful in the con- 
trol of cockroaches in tropical and damp cli- 
mates. Its use is advisable in cases where 
roaches are present but not especially numerous. 
It is particularly effective against the 
Araerican cockroach. 
Biosphorus paste is prepared commer- 
cially from yellow phosphorus. Essentially 
these pastes are made by grinding the yellov/ 
phosphorus in the presence of water and then 
mixing v/ith flour in the proper proportion. 
Glycerine is sometimes used as an ingredient. 
Commercial preparations usually contain from 
1 to 2 percent of phosphorus. 
Yellow phosphorus is a v>diite to yellow- 
ish, translucent, waxy solid, which turns more 
yellow as it ages. VJhen exposed to air it 
takes fire at 34° C. (93.2° F. ) and burns with 
a yellowish flame. 
Caution ; Phosphorus paste, because of 
its very poisonous nature, should be handled 
with the greatest of care. Since the yellow 
phosphorus is so inflammable and poisonous, 
it is safer to purchase the commercial paste 
rather than attempt to prepare it. 
