64 
of thymol. A mixture,. of 0.2 part of concentrated,nitrid ^acid: and 100 parts 
of hydrochloric acid v/as then added and the solution shaken, k "blue-green 
to blue color appeared in from 30 seconds to 2 minutes vrhen rotenone was 
present. The following quantitative test vas designed for use with colorless 
liquid insecticides; 
To 10 ml. of a chloroform solution containing from about 
0.05 to 2.5 mg. of rotenone per milliliter in a glass-stoppered 
cylinder, add 10 ml. of a chloroform solution of thymol (lO gm. 
of thymol to 100 ml. of chloroform) and -2 ml. of a reagent made 
by adding 2.5 ml. of o-percent hydrogen peroxide to 100 ml. of 
concentrated hydrochloric acid. (When the sample is not in 
solution in a hydrocarbon base, concentrated hydrochloric-acid 
may be used in place of this reagent.) Agitate for 1 minute, 
loosen the glass stopper, and expose the- cylinder to the intense 
radiation of a quartz-mercury vapor lamp (minimum output 1000 
microwatts per square cubic centi.-n.eter in the field of exposure). 
A greenish-blue color apoears in the chloroform layer in about 
15 minutes. (Exposure to bright sunlight produces simil-^r results 
in about 3 hours.) At the end of 30 minutes compare with stand- 
ards containing known quantities of pure rotenone prepared 
simultaneously in the same w^y. If the insecticide base is refined 
kerosene, use an equal amount of refined keresene in preparing the 
standards. ' 
. A more rapid method making use of an acetone solution was as follows: 
To 5 ml. of an ecetone solution containing 0.1 to 2.0 mg. of 
rotenone per milliliter add 5 ml. of an acetone solution of 
thymol (IC gra. of thjTnol to 100 ml. of acetone), 0.1 ml.' of 3- 
percent hydrogen peroxide, and 5 ml. of concentrated hydrochloric 
acid. A reddish-violet color aooears v/ithin 30 seconds. After 
1 minute place the cylinder in a water bath at about 20^ C, and 
at the end of 20 minutes compare with rotenone standards similarly 
pre-oared at the same time. 
If the liquid extract contained pyrethrura extract, it was recommended tnat 
a standard containing pyrethrum extract be prepared to match the original 
color of the liquid insecticide. 
Cahn and Boam (l4) in the same year reported failure to obtain the 
Rogers and Calamari qualitative test with the rapidity and intensity 
stated by the authors of the test. These factors were fo\ind to be markedly 
affect d by the nitrous acid content of the nitric acid. With a mixture of 
fresh nitric and hydrochloric acids the rotenone color was produced only 
slowly. V/hen nitrite was added to the mixture, or vrhen the acid mixture 
was allowed to stand before use, the rotenone color developed rapidly. It 
Was concluded that the reaction depended more upon the presence or 
production of nitrous acid than upon the presence of nitric acid. 
In their reply Rogers and Calamari (l03) stated that it was essential 
to use concentrated hydrochloric acid containing not less than 35 percent 
