POTASSIUM SULPHOCYANIDE. 137 



.avindare, Mouillefert placed in six holes, 6 grammes, say 91 grains, of 

 KCNS, dissolved in a litre of water (6 parts in 1000). Next morning. 

 :all the young plants were dead. The adult plants had suffered greatly. 



(2) Experiments on Healthy Vines in Pot.- — Half a gramme of 

 KCNS in 250 cubic centimetres water (1 in 500) and spread round the 

 stock killed it in five days. KCNS thus has a very injurious action on 

 plants, an action almost equal to potassium cyanide. As it does not act 

 by its vapours, its action on the plant depends solely on the permeability 

 •of the soil for its solutions. This explains why equal doses do not always 

 produce identical effects. The same applies to aqueous solutions of 

 all stable salts. Kranch treated barley with (NHJCNS, and found 

 that a 1 per cent solution killed this plant. 



Action on Fungi. — Sulphocyanides do not act like cyanides 

 (Hitchcock and Carleton). A 1 per cent solution used in immersion 

 for twenty-four hours did not prevent the uredospores of Puccinia 

 coronata from germinating. 



Action on Insects. — Mouillefert treated phylloxera-infected vines 

 with a dilute solution of KCNS. An infected pot plant was watered 

 with the dose recognized as capable of killing the vine, say 0*5 gramme, 

 dissolved in 250 cubic centimetres of water. Whilst the vine was 

 poisoned the phylloxera were uninjured. Sulphocyanide, very ener- 

 getic on plants, is thus with the same dose without action on the 

 phylloxera and cannot thus be used against it. 



Addendum to Chapter VII., p. 129 — being omission from Section 

 35, Potassium Sulphocarbonate : — 



Tipula Oleracea (meadow tipula). — To destroy the larvae of 

 tipula, carbon disulphide may be replaced by spraying meadows and 

 fields with a dilute solution of potassium sulphocarbonate. Barthon, 

 who recommends this treatment, advises to test previously the dose 

 which will not injure the plants on which it is to be applied. A 

 solution of 0-1 to 0-5 per cent never injures plants and kills all under- 

 ground larvae. 



