A NEGLECTED FACTOR IN THE USE OF NICOTINE 

 SULPHATE AS A SPRAY ^ 



By William Moore, Head of Section of Research in Economic Zoology, and SamuEI 

 A. Graham, Assistant in Entomology, Minnesota Agricultural Experiment Station 



The attention of the authors was directed recently to a case of nico- 

 tine poisoning resulting from the use of greenhouse lettuce {Lactuca 

 saliva). Thinking this an isolated case due to some florist's cutting his 

 lettuce near the time of spraying with a tobacco extract, they took no 

 further notice of this case. About a week later an entire family of nine, 

 after eating leaf lettuce, became ill, showing distinct symptoms of nico- 

 tine poisoning. The lettuce was traced to the florist who had grown it, 

 and further inquiry showed that his lettuce had been responsible for 

 both cases of poisoning. 



A few heads of this lettuce, crushed and distilled under alkaline condi- 

 tions, gave a distillate with a distinct odor of nicotine.^ The distillate 

 gave characteristic reactions of nicotine when treated with mercuric 

 chlorid, with a solution of iodin in iodid of potassium, and with a solu- 

 tion of mercuric and potassium iodid. 



This test was carried out 12 days after the florist had sprayed his 

 plants with a well-known commercial tobacco extract, containing 40 

 per cent of nicotine sulphate, using it, according to his statement, at the 

 rate of i teaspoonful to i gallon of water. Other growers in the vicinity 

 have used commercial tobacco extracts containing 40 per cent of free 

 nicotine for years, even selling lettuce the day after spraying without 

 causing any illness to the consumers. The question arose as to why the 

 spray containing nicotine sulphate remained on the plants for 12 days, 

 while similar sprays containing free nicotine quickly disappeared. 



A COMPARISON OF NICOTINE AND NICOTINE SULPHATE 



Nicotine is volatile, in fact very volatile, when one considers that its 

 boiling point is 250° C. When sprays containing free nicotine are used, 

 the nicotine quickly evaporates from the plant, leaving no trace when 

 tested chemically the day after the spraying, even where used at the rate 

 of I part to 100 parts of water. Fumigation with tobacco papers con- 

 taining free nicotine left no trace of nicotine on lettuce leaves the morning 

 after fumigation, even before the plants were sprinkled. Commercial 



1 Published, with the approval of the Director, as Paper No. 6i of the Journal Series of the Minnesota 

 Agricultural Experiment Station. 



^ The authors wish to express their thanks to Dr. R. A. Gortner and Mr. J. J. Willaman for assistance in 

 the chemical analysis given in this paper. 



Journal of Agricultural Research, Vol. X, No. i 



Washington, D. C. July 2, 1917 



OS Key No. Minn. — 16 



(47) 



