48 Journal of AgricuUural Research voi. x. no. i 



tobacco extracts containing free nicotine are stated by the manufacturers 

 to be for indoor use. On the other hand, commercial extracts containing 

 nicotine sulphate are for outdoor use, the reason given by one manufac- 

 turer being that "sulphate of nicotine does not evaporate as quickly as 

 free nicotine. " Mclndoo ^ claims that nicotine sulphate kills insects by 

 its vapor in the same manner as nicotine. He mentions the death of 

 insects from the odor and also the vapor of nicotine sulphate. 



The first point in the investigation was to determine the volatility of 

 nicotine sulphate. Pure nicotine was treated with concentrated sul- 

 phuric acid, and this mixture was then heated over a steam radiator for 

 15 hours to evaporate any free nicotine which might be present. The 

 compound thus obtained was a dark-brown, sirupy mass with no odor. 

 Later this was found to contain a number of crystals. 



This compound was first tested upon house flies. One-liter Florence 

 flasks were used as fumigation chambers. The flies were introduced 

 into the flask and the neck closed with wire netting to prevent their 

 gaining access to the nicotine sulphate, which was placed on a piece of 

 filter paper suspended from the stopper. The stopper was rubber, cov- 

 ered with lead foil to prevent any absorption of vapor. Pure nicotine 

 under such conditions will kill house, flies within three hours, but the 

 nicotine sulphate failed to kill them within the time a house fly will 

 remain alive in such confinement. Commercial 40 per cent nicotine 

 sulphate killed the flies in from three to six hours. In order to test these 

 compounds further, the common croton bug {Blatella gerrnanica) was 

 used, as it will live in such confinement for a long time. Pure nicotine 

 killed these insects in 3>^ days, while those in the flasks containing com- 

 mercial 40 per cent nicotine sulphate and pure nicotine sulphate were 

 alive and active 10 days later. 



Allen ^ states that on treating a solution of nicotine sulphate with an 

 alkali the sulphuric acid will act just as if it were uncombined. The 

 addition of soap to the nicotine sulphate in sufficient quantities to ren- 

 der it alkaline would therefore free the nicotine. The nicotine sulphate 

 in one flask was rendered alkaline with soap, and it was then found that 

 cockroaches in this flask died in the same length of time as those treated 

 with pure nicotine. From these results it would appear that nicotine 

 sulphate was nonvolatile. To test this point further, an attempt was 

 made to distill the pure nicotine sulphate with steam. The result of 

 this test was negative. On rendering the nicotine sulphate alkaline and 

 again distilling with steam, the nicotine passed over in abundance. The 

 distillation of commercial 40 per cent nicotine sulphate with steam 

 showed that these preparations contain from i to 2 per cent of free 

 nicotine. 



1 McIndoo, N. E. effects of nicotine as an imsectide. In Jour. Agr. Research, v. 7, no. 3. p. 

 89-122, 3 pi. 1916. Literature cited, p. 120-122. 



2 Allen. A. H. commercial organic analysis ... v. 3. pt. 2, p. iSj. Philadelphia, 1902. 



