372 INSECTICIDES, FUNGICIDES, AND WEED KILLEES. 



insects.) (5) Add to a 2 per cent tobacco juice a little carbolic acid. 



(6) Add to 4 lb. of the above carbolized tobacco juice 1-^ lb. of creoline, 

 1 lb. of soft soap dissolved in 10 gallons of water (Zechini and Silva). 



(7) Dissolve 3 lb. of soft soap, in 5 gallons of water, add thei'eto a 

 solution of 2^ lb. of blue vitriol, neutralize by 11 lb. of caustic potash. 

 After stirring well run in 5^ lb. of tobacco juice and 2^ lb. of " creoline ". 



Properties. — Tobacco juice is characterized by a special alkaloid 

 nicotine. Pure nicotine is an oily liquid, colourless, soluble in water, 

 alcohol, and fatty oils ; it precipitates almost all metals from solutions 

 of their salts ; with copper it yields a green precipitate soluble in a large 

 excess of nicotine. Nicotine is a violent poison to mammals. A 

 single drop of nicotine suffices to kill a dog. It causes giddiness, 

 abdominal pains, followed by death in a few minutes. 



Action on Plants. — Tobacco juice is used as an insecticide in 

 1 per cent doses, say O'l per cent of nicotine. It injures plants ; 

 mixtures with soap still further increase its injurious action. To 

 obviate this drawback it is necessary to follow the sprayings by care- 

 ful washing after one houi-'s interval. Fumigations in greenhouses 

 are less to be feared for the plants ; however, Decaisne has observed that 

 cei'tain greenhouse (scrrefroide) orchids stand this treatment badly. 



Action on Insects. — Nicotine is a violent poison for most insects 

 and their larvae. Chittenden observed that it did not act so on all 

 insects. A solution of O'l per cent (1 per cent of the rich juice of the 

 French manufactories), especially if it contains 1 per cent of soap, 

 forms an energetic liquid against the most diverse insects. If the 

 published results do not always agree that is due to the different 

 nicotine content of the juices tested on the same insects. It is agreed that 

 nicotine solutions have a specific action on the caterpillars of butterflies, 

 the false caterpillars of the saw-flies, on non-protected lice, thrips, and 

 acari. In closed spaces the action of the vapours of nicotine is 

 drastic even on cochineals. 



Use. — In enclosed spaces, greenhouses, or spaces covered in for 

 the purpose, the following process is used to obtain entire disinfection 

 of the plants therein : — 



Fumigation or Evaporation of Nicotine in a Closed Space.— 

 It is carried out in different ways : (1) Tobacco is laid in a special 

 apparatus outside the greenhouse above red-hot coals, the combustion 

 of which is accelerated by a bellows. A pipe leads the vapours charged 

 with nicotine inside the enclosed space. (2) Moisten tobacco leaves and 

 place them on the hot pipes of the hothouse. The water evaporated 

 carries sufficient nicotine to kill the insects. (3) Slow evaporation 

 inside the greenhouse of tobacco juice placed on small stoves. (4) 

 Projection of tobacco juice on strongly heated bricks or irons. 



Use in Open Air. — ^Open-air plants infested by insects are 

 sprayed with tobacco juice diluted with water to contain 1 per cent 

 of rich juice. Nicotine solutions not moistening sufficiently the insects 

 touched it is better to use soapy bouillies which adhere and moisten 

 much better and thus act more quickly. After one hour the insects 

 touched ai'e dead ; the plants treated must then be washed to prevent 

 the deadly action of the nicotine and the soap on the plant. 



