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efficiencies viere ^nnp.'basine s^ulfate 100, anatasine naphthenate 98, 
analDasine 96, anatasine resinate 35, and lupinine 3. The relative 
decrease in the effectiveness of anabasine naphthenate rrhen combined 
T7ith naphthene soap v:as probably d-iie to a decrease of the hydrolysis 
of the soap as the result of the presence in the spray of ions of 
n3.phthene acid from t'-zo sources (the soap and the pjiabasine naphthenate), 
so that the concentration of the free naphthene acid, tvhich possesses an 
independent insecticidal action, '^as reduced. Fron these tests it is 
concluded that anabasine resinate and lupinine are unsuitable for use in 
insecticides. 
Further tests on ilyzus persicae , in rrhich various concentra.tions of 
anabasine and ?xiabasine sulfate were used vrith 0.4 percent of naphthene 
soap, and anabasine naphthenate was used alone, sho^ved that the latter 
spray TToiild be the cheapest, since even at a concentration of 0,03 per- 
cent it killed 96 percent of the aphids. Tlie a,ddition of mineral oil 
emulsions or of small quantities of "Conta.ct" or pectin glue considerably 
increased the effectiveness for anabasine. 
■~ith a vie-;: to deter.ninin^- tha factors on vhich the effectiveness 
of these preparations depends, the physico-chemical properties of the 
solutions r/ere studied and are discussed in detail. It r:as found that 
the hydro::^:en-ion concentration exercises a considerable influence on the 
effectiveness of the spray, chiefly in the case of cliff erent solutions 
of the same prepa.ration. 'Vith the a.ddition of naphthene soap all the 
preparations acquired an ?.lkaline reaction, r/hereas the addition of 
large q-cantities of "Contact" or pectin jjlue considerablj'- increased the 
concentration of the hj'drogen ions, vrhich reduced the effectiveness of 
the spray. Tith a decrease of the s'xrface tension and viscositj'- the 
effectiveness of the spr.ay usually increased. There is a certain 
antagonism of action bet^Teen surface tension on one side and viscosity 
and pH on the other. A high, concentration of hydrogen ions and high 
viscosity usually neutralizes the effect of lo- s'jrface tension. 
It appears that the bicyclic alkaloids are more toxic thaji the mono- 
cyclic ones. The insecticidal properties of alka,loids that are similar 
in structure depend on the elasticity and volatility of their vapors, 
but their toxicity is eq-ua.lly decreased uhen volatility is too high or 
too lor;. The comparative effectiveness of the r;ater solutions of 
nicotine or anaba.sine rjid their salts also depends on the volatility of 
the vapors since, '7hen applied as sprays, they act as f-omigajits. The 
volatile ajiabasine and nicotine rapidly form high concentrations but do 
not maintain them for long, vrhereas the corresponding salts eva.porate 
sloTTly and keep up a definite concentration of vapors dviring a prolonged 
period, rrhich explains their relatively grea.ter effectiveness. 
The authors suggest the use of the term ''effectiveness" instead of 
"toxicity" to express the insecticidal value of alkaloids in sprays. 
Under these conditions the alkaloids and their salts possess equal 
potential toxicity, as the active principle of both is the alkaloid that 
penetrates into the body of the insect in a vaporous or gaseous state 
through the tracheal system. The insecticidal action, therefore, does 
not depend on the different toxicity of the preparations, but on the 
effect of the physical properties of the solutions on the rate of 
evaporation and penetration of the alkaloid into the tracheae. 
