POTASSIUM SULPHOCARBONATE. 125 



sulphocarbonates. In a 2 -litre flask with moist sides into which 

 -| cubic centimetre of sulphocarbonate of potash of 40'^ B. had been 

 run, the phylloxeras of an infested root suspended in this flask were 

 killed in three hours. By running in 4 cubic centimetres of this pro- 

 duct the insects were killed in half an hour. Now -^ cubic centimetre 

 contained 0-354 of dry sulphocarbonate capable of emitting by decom- 

 position 0'14 gramme of carbon disulphide, or 40 cubic centimetres, 

 and 0-06 gramme of sulphuretted hydrogen, or 40 cubic centimetres 

 of gas, giving a total of 80 cubic centimetres of poisonous gas. It may 

 therefore be concluded that ^ cubic centimetre of sulphocarbonate is 

 capable of producing in 2 litres of air an atmosphere with 4 per 

 cent of toxic gases. 



In trials with ^^j cubic centimetres of sulphocarbonate, or with 100 

 cubic centimetres of a 0-1 per cent solution, capable of producing 16 

 cubic centimetres of poisonous gas, and consequently an atmosphere of 

 0-8 per cent, the insects were killed in twenty-four hours. Now it is 

 admitted that sulphuretted hydrogen destroys the phylloxera in twenty- 

 four hours when the air contains 1 per cent of this gas, and carbon disul- 

 phide when the atmosphere contains 0-5 per cent of its vapours. It 

 has been seen that the sulphocarbonate of potash disengages the same 

 volume of these two gases. It follows that a mixture of equal volumes 

 of sulphuretted hydrogen and carbon disulphide in the gaseous state 

 would kill it in twenty-four hours with a solution of 0-75 per cent 

 strength. The result obtained is thus appreciably the same as that 

 found for sulphocarbonate of potash. The mixture of the two gases 

 produced by the decomposition of the sulphocarbonates kills the 

 phylloxera in the same time as a mixture of the same quantities of 

 these two gases acting simultaneously. But sulphocarbonates do not 

 act only when they eater iato decomposition, their solutions are in 

 themselves powerful insecticides. Whilst both gases jDroduced by the 

 decomposition do not kill the phylloxera except at O'OOIS per cent 

 the sulphocarbonates in solution kill at 0-0005 per cent. Sulpho- 

 carbonates may thus be regarded as the most powerful of disinfectants, 

 their aqueous solution being three times more powerful than 

 sulphuretted hydrogen gas and carbon disulphide. Owung to this 

 property, alkaline sulphocarbonates may be used to distribute through 

 the soil substances highly poisonous to insects. There is no difference 

 in the action of the different salts of sulphoearbonic acid, potassium 

 sodium, or calcium salts, but the former are generally used because they 

 possess the advantage of carrying into the soil a certain amount of 

 potash, which, in certain circumstances, may contribute to the rapid 

 recoastitution of the damaged root system. The doses used in the 

 laboratory to kill the phylloxera are not those which are of use on the 

 large scale, because many causes contribute to reduce their efiiciency. 

 The doses tried by Mouillefert were at first very strong, and killed 

 •the vine, treated as well as the parasites. The soil was watered 

 from small vats near the stocks with a solution of 400 cubic centi- 

 metres of sulphocarbonate of potash of 38° B. in 5 litres of water, 

 then with 8 litres of pure water. In other cases he used 220 cubic 

 centimetres of sodium sulphocarbonate of 45° B. dissolved in | litre of 



