§Q AXM Ai. Ki;i'ni:rs <»i- I ti:!' \iMMi:.\'r of a* ;ki( ri/irKi:, wm 
Forty-six ai liclcs wi-rc i»Ml»lislic<l. mostly in journals outside tlic I ►cpartiiuMit. 
Ki>;lit patents (»n various new insect i< i(les and methods of making them, and ou 
new wasliin^r solutions I'or removing inseet icidal spray residues frtmi apples, 
were jjranted memhers of the Division. Tho monthly review f»f United States 
patents relating' to jtest control was issued re^rularly tlirout;h<»ut the year and 
was sent to l.l.Ti American and 2H.'i foreign entomologists. 
CHEMICAL INVESTIGATIONS ON INSECTICIDAL PLANTS (T()BA( ( (). DERKIS, 
PYKETHKLM. ET( .) AND THEIR CONSTITl ENTS 
Studies on the chemistry of i)yrethrum llowers have heen continued. 
I'yicthrum llowers are used in the nianufacture of hoii.sehold inse<'ticides in- 
tended lor combat ing Ilies, lleas. mo<(|uitoes. r»»aches. etc.. in cattle sjirays. and in 
dusts for the treat meul of celery, cabbage, and numerous other crops. From 
10. tMiO.OOO to ir),(M)(MH)() i)ounds of this imj)ortanr insecticide are imi>orted yearly, 
and it is highly desirable to know more about its chemistry. One of the objects 
of these studies is the isolation of pure pyrethrin I and i)ure pyrethrin II in 
order that their relative in.secticidal efficacies can be studied. Methods were 
worked out for obtaining the semicarbazone of pyrethrin II in pure form, but 
no .scheme could be found for hydrolyzing this compound to yield i)ure pyrethrin 
11. The .semicarbazone of pyrethrin I, on the other hand, is always obtained 
quite impure, and it wa.s finally determined that it is always accompanied by 
some of the semicarbazone of i)yrethrin II, and by the .semicarbazone of 
jiyrethi-oloiM' esters of palnutic and linoleic acids. Attemjits to reirenerate 
l»yretlirin IT from pyrethrolone and chrysanthemum dicarboxylic acid yielded 
a product not identical with natural pyrethrin II. It was found further that 
the spatial configuration of pyrethrolone is the .same whether obtained from 
])yrethrin I or pyrethrin II, and that the pyrethrins can be cleaved by catalytic 
hydrogen with tlie formation of dihydrojasmone. a perfume. Extensive studies 
were carried out on the uature of the side chain of pyrethrolone. which is im- 
portant becau.se of the marked specificity of the pyrethrins to insect.s. The 
exact position of the double bonds was not demou.strated conclusively, but the 
ex idence favors an allene system rather than a conjugated system. 
The question of the presence of nicotine and other alkaloids in species other 
than \irotiati<i tahariini was furtlu^r investig.ited. It w.js discovered that .V. 
s 1/1 rest rifi contains 1-nornicotine. This ])lant is the only known .source of this 
alkaloid, which is more toxic than nicotine and hence of in.secticidal interest. 
A .study of N. dchneiil revealed the pre.'^ence of anabasine and nicotine. It 
became necessary to study the sejiaration of nicotine from the other alkaloids, 
and a method involving distillation of aqueous solutions was developed for 
separating anabasine and nicotine with great accuracy. The preparation and 
])roperti<'s of nicotine-]i(>at were* studiivl further. 1 2no ]iou?ids lieintr prepared 
in the I>e))artment's laboratories for field use of the Bureau during the present 
.season. The great(>r stability of nicotine tannate over nicotine sulphate was 
demonstrated by residue studies, and a rather rapid decomposition of nicotine 
by air was demonstrat(Ml. Two articles describing a gravimetric micriM-hemical 
method for determining small amounts of nicotine W(>n^ i)ublished. In addi- 
tion, for a study of the evolution of nicotine from dusting mixtures containing 
it. there was developed another new microchemical technique involving titra- 
tion of the nicotine with silicol nngstic acid, tlu^ end point being rec<»gnized 
as tlie point of maximum turbidity as men-sured by a photo(^lectric device. 
The fpiestion of rotenonc and i^lauts bearing if was again given <-(»nsider- 
able attention. The worlc of devisiuir n satisfactory method of determining 
rofenone was brought to conclusion; the crystalli/.at ion proci'dure was <le- 
scribed in a i)ublished articl(\ and the d(>fails of the extraction pr»»cedure 
are now in manuscript form. In a<lditi(»n. a i»ossibIe new analytical ])roc:»dure. 
in\ olving a chemical estimation of the rot(Mione rather than its sei».irat ion 
by crystallization, was dcveloi)ed and is Ixung tested. The sohibility of 
roleno'ie was det<'rmined in ."."» connujM'cial organic solvtMits not In'retofore 
re]>orte<l upon. The i»hysical ]U"o])erties of the complex which rotenoix^ 
forms with carbon tet r.-ichloride were inv(^st igated. bec;nise of thi^ import.-uice 
• •f this conqK»und in the an;ilysis nf dcrri^ ;ind cub(>. 
'{'be sl\idy of the retardation of the deconqtosit ion of dcrris w;is continued, 
(bit of 110 si)ray combinations studied In the laboratory, the l."» that showiul 
some i»romise from the chemical jxtinf of \ iew wer«» i»repared for careful 
insecficidal testing duiini: flii^ ^nninier. 
