124 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



grammes of carlion Jisulphide and 1"35 gi-amme of sulphuretted 

 hydrogen, quantities which are supported by the vine in similar condi- 

 tions, especially in emulsion in water. It takes more than & cubic 

 centimetres of sulphide emulsified in 60 cubic centimetres of water to 

 kill the vino at that period. Young adventitious plants {Mercurialis 

 annua, Polygonum avicidare, Calenchda arrensis, Borrago officinalis, 

 Erodium eicutarium, Ictaria viridis) vegetating in the open air were 

 treated at end of August with 100 cubic centimetres of sulphocarbouate 

 of potassium or sodium of 15° B., reduced so as to make 2 htres of 

 mixture, and spread in five holes in a square of 20-inch side ; the plants 

 only suffered in the immediate neighbourhood of the holes. Haricots 

 planted in pots containing 2 litres of soil resist perfectly when 

 watered with 250 grammes ot a 2 per ceat solution of 45° B. potassium 

 sulphocarbonate. Now, in practice, such strong doses are never used 

 against insects. The toxic effect of potassium sulphocarbonate on 

 plants is therefore almost negligible, whilst the dose is always poisonous 

 to insects in a 0-0005 per cent solution. 



Action on Fungi. — Like carbon disulphide potassium sulpho- 

 carbonate in strong doses exerts an injurious action on the mycelium 

 of fungi and their spores. Dufour and Mouillefert tried this com- 

 pound to replace carbon disulphide against root blight, Demato'phora 

 necatrix, Hartig. They did not, however, obtain the good results 

 which they anticipated. Dufour only registered 15 per cent of cures 

 after treating the stocks of vines suffering from the blight by a 2 per 

 cent solution at the rate of 3-5 litres per stock. It is true, that in 

 these trials Dufour is far from having fed into the soil a dose of 150- 

 200 grammes of carbon disulphide per square metre, as is the case 

 in the treatment of root blight by carbon disulphide, for the 100 

 grammes of liquid sulphocarbonate used in this case only contained 

 15 grammes of sulphide. Sulphocarbonates cannot replace the sulphide 

 in the treatment of root blight, for they are much dearer. It is only 

 when the dose of sulphide is minimum, as in the case of some insects, 

 that the sulphocarbonates present real advantages over carbon di- 

 sulphide. 



Action on Insects. — Sulphocarbonates, owing to their composi- 

 tion, are almost equally as efficient as potassium cyanide. The most 

 dilute solutions have a manifest and rapid action on insects. Mouille- 

 fert examined very exactly the limit of action of sulphocarbonates 

 used against the phylloxera in different ways. 



1. By contact. — By dipping the insects into dilute solutions, 1 in 

 200 of sulphocarbonate of 38° B., the insects were found dead in a 

 quarter of an hour ; in 1 in 500, in one hour ; in 1 in 1000, in one 

 hour fifteen minutes ; in 1 in 5000, one hour ; in 1 in 10,000, two hours 

 fifteen minutes; in 1 in 100,000, in twenty-four hours. In a blank 

 flask only containing water the insects were not dead in twenty-four 

 hours. The potassium sulphocarbonate of 38° B. used in these trials 

 not containing 50 per cent of dry sulphocarbonate, it may be said that 

 the action of this product is deadly to the phylloxera in twenty-four 

 hours in a 1 in 200,000 solution, say 0-0005 per cent of dry salt. 



2. By the toxic vajjoiirs disengaged by the decomposition of the 



