53 
(Joodhue and Haller (^2) in 1940 used this method for the estimation of 
dihydrorctenone in the liydrc? -'nation products of rotenane. Altnoufljh this 
derivative of rotenonr hrs rol: "been foand in dtrri3 £u~id cu-je roots, the modified 
procedure is equally rpplicahlG to the det^niAnatio-i of rotenone and dc^jielin 
in extracts of these plants. The procedure was practically identical vdth 
Goodhue's earlier modification (4C0 of the test eycept th;:it 6 cc.( instead of 5 
ccO of dilute sulfuric acikl was used follov/ln/? the addition of ali-iali and the 
solution vas then maintained in a cold-water bath at 15 to ?-00 C. for ahout 5 
minutes (instead of at 25^ for a lon^^jer period). Howe-'rer, the rneasurement of 
the color intensity was ir.-proved. Thi3 pc:.?tion of the procedure was as followst 
"The use of a photometer has "been found to "be thf^ most tconir-tte 
method of con:paring the standards and the unknov.TiS. Tha colors crj:i 
be developed dix-ecoly in selected test tribes v/hich fit the photometer, 
or they can be dcveloxicd in sny test tube and poured into a rpecial 
'.-cell. A Brice photometer which g-ives percentage transniiscion as ai.rect 
readings has been found satiefactory. Glass filters (CorrJ.ng, Z,5 mm., 
No. 430, dark shads blv.e-groer) were used. The blanic is taJcen as 100 
percent trajismission, rnd the photometer is therefore adjusted to give 
a, reading of 100 vdth the cell containing the bian'x: in place. The 
readings for the standards and -unknowns --rhiah are next obtained are 
therefore in percent trensml3F.ion. 
"*»**'the color for rotenone has b^en four-.d by Cpssil (unpublished) 
to follow Peer's lav*-''-^/ A plot is therefore made on 3emilf>-^a^ithmic 
paper with transmission as orainato (logaritimaic) and concentration as 
-sbaclssa (arithmetic), and a straight line is dra-.vn from the point of 
zero concentration and 100 percent transmission to the point determined 
by the concentration and the transjuission of th'^ stai:dard. The trazis- 
mission of the unknown having been determined, its concentration can be 
read from the curve and the percentage calcuirted." 
Cassil (19) in 1941 used tne red color test for the determination of 
derris-du.st rec.idues on cabbages. The residues were extracted by washing the 
leaves with chloroform, the extract evaoorated, and the residiue dissolved in 
hot acetone. The acetone solution was chilled to remove wft.T.y material, and the 
filtered solution was used for the color test. The colors v^ere ccmorred with 
those from extracts of kno^'m quantities of the derri^' root actually used in the 
original dusts. Comparisons of color intensity were made in a photoelectric 
photometer. 
