350 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 12: 



nicotine has a stronger odor than either the preparation containing 

 the 43 per cent or the 100 per cent, the 43 per cent having very little 

 odor indeed. The preparation of 40 per cent nicotine as sulphate has 

 a stronger odor than the preparation of 100 per cent "free" nicotine 

 and is again of a different character than the odor of any of the other 

 nicotine preparations. 



Color No Indication of Comparative Strength. — We have been 

 accustomed to believing that the higher nicotine concentration, the 

 darker the color. The coloring matter is almost entirely due to mate- 

 rials other than the nicotine extracted from the tobacco plant. The 

 preparations mentioned above in demonstrating that odor has no- 

 relation to nicotine strength may also be used to show that color is 

 no indication of comparative nicotine content. The preparations 

 containing 43 per cent and 100 per cent nicotine are almost the same 

 in color — a transparent red — and both are clearer and lighter in color 

 than the 40 per cent nicotine as sulphate and the nicotine — free 

 tobacco oil, both of which are dark brown in color, almost opaque, and 

 heavier than the other preparations. 



Per Cent Nicotine Content Alone Insufficient as Statement- 

 OF Exact Strength. — Most of the commercial nicotine solutions on 

 the market contain 40 per cent nicotine by weight. The nicotine may 

 be in the form of "free" nicotine or in the foi'm of nicotine sulphate, 

 but the per cent refers to the amount of nicotine, by weight, because- 

 it is the only method of knowing definitely how much actual nicotine 

 is contained in the solution and such designation is required by the 

 Federal Insecticide Board. It is necessary, then, to know the specific 

 gravity of the preparation in order to know the actual nicotine content. 



Below is a list of three commercial preparations, each containing: 

 40 per cent nicotine bj^ weight, showing the variations that exist in- 

 several preparations. 



Dilutions, being by volume, would in the case of each of the above 

 40 per cent preparations give solutions of widely different nicotine 

 content, granting that the same dilution is used with each preparation. 



Per Cent Nicotine Content together with Specific Gravity 

 Constitutes' Statement of Exact Strength and Comparative: 

 Value. — In order to know the definite value of a nicotine solution,. 



