396 
Journal of Agricultural Research 
Vol. VII, No. 9 
8 % ounces of nicotine was 95.9 per cent, the highest of any of the for¬ 
mulae used in these experiments. This point of concentration is appar¬ 
ently the optimum, as the efficiency dropped to 86.8 per cent when 10 
ounces of nicotine sulphate were used. The curve for the sprays in 
group 3 shows that the efficiency increases from 36.1 per cent for the 
formula containing ounces to 69 per cent for the formula containing 
6X ounces of nicotine sulphate. From this point the efficiency rises 
gradually to 75 per cent for the formula containing 10 ounces of nicotine 
sulphate. 
The wetting powers of the solutions in group 2 fall gradually from 788 
for the formula containing 3^ ounces to 732 for the formula containing 
8 $i ounces of nicotine sulphate. Further concentration of the nicotine 
in the solution causes a considerable loss of wetting power, and the 
formula containing 10 ounces of nicotine has a wetting power of only 628. 
The wetting-power curve of the solutions in group 3 falls gradually from 
181 for the formula containing 3^ ounces to 103 for the formula con¬ 
taining 10 ounces of nicotine sulphate to 50 gallons of solution. 
DISCUSSION OF GROUPS 2 AND 3 
The main facts to be noted from the results given in figure 2 are: (i)The 
addition of 5 pounds of soap to the 50 gallons of nicotine solution in¬ 
creased the efficiency from 20 to 30 per cent more than that of similar 
nicotine solutions which contained only 1 pound of soap to 50 gallons 
of water; (2) the most efficient results were obtained with formulae con¬ 
taining 5 pounds of soap, 6 % to 8 % ounces of nicotine sulphate, and 50 
gallons of water; (3) when more than 8$4 ounces of nicotine were added 
to the 5-to-5o soap solution there was a loss of efficiency and likewise a 
corresponding loss of wetting power; (4) while the quantities of soap in 
the solutions remained constant through both groups of formulae, there 
was a gradual loss of wetting power, as the quantity of nicotine was in¬ 
creased in the solutions. The results derived from the formulae in 
group 2 support the deductions already drawn from the results obtained 
with the formulae in group 1—namely, that when certain concentrations 
of the soap and nicotine are reached, not only is there a decided loss of 
wetting power but there is also a corresponding loss in the insecticidal 
efficacy of the sprays. If nicotine sulphate is used at the rate of 1 to 
630, the optimum efficiency is obtained with 4 pounds of soap to 50 
gallons of water. By reducing the concentration of nicotine sulphate 
to 1 to 720, 5 pounds of soap to 50 gallons of solution gives the greater 
efficiency. The effect which a loss of wetting power may have upon 
the efficiency of a solution is indeterminable, since soap, as well as nico¬ 
tine, has insecticidal properties. Thus, it is probable that a reaction 
which would cause a loss of wetting power would also reduce the insec¬ 
ticidal properties of the soap, ending in a loss of efficiency. There is 
