﻿2 00 FIELD AND FOREST. 



seventh of sulphur compounds. It was only with some of the substan- 

 ces contained in this last group that really satisfactory results were 

 obtained, and it is to M. Dumas, the permanent secretary of the 

 French Academy of Sciences, that the credit is due for suggesting the 

 employment of the alkaline sulpho-carbonates of potassium and so- 

 dium and those of barium and calcium. All the other classes of rem- 

 dies mentioned above were either without effect on the Phylloxera, or 

 in destroying it, also destroyed or damaged the vine. 



The sulpho-carbonates, which were carefully studied by the great 

 Swedish chemist Berzelius, are obtained by combining the alkaline 

 mono-sulphides, with the bi-sulphide of carbon, are either liquid or 

 solid and emit a powerful odor of sulphuretted hydrogen and bi-sul- 

 phide of caroon. 



The alkaline sulpho-carbonates in solid states are of a beautiful red- 

 dish color and deliquescent, but are not easily obtainable in that con- 

 dition ; the sulpho-carbonate of barium can be easily procured, how- 

 ever, in a solid state, and presents the appearance of a yellow powder, 

 but little soluble in water. The sulpho-carbonates decompose under 

 the influence of carbonic acid, forming a carbonate, and evolving sul- 

 phuretted hydrogen and bi-sulphide of carbon. These two latter 

 substances are gradually liberated and, as they have a very powerful 

 effect on the Phylloxera, one can understand that the sulpho-carbo- 

 nate placed in the ground, may prove by its slow decomposition, a 

 powerful insecticide. In the case of the sulpho-carbonate of potas- 

 sium, over and above its toxic effect, it has a direct invigorating in- 

 fluence upon the vine, as the carbonate of potassium is an excellent 

 manure. 



The employment of the sulpho-carbonates as a means for the des- 

 truction of the Phylloxera, was suggested to M. Dumas, by the clearly 

 recognized need that there was of some substance that would evapo- 

 rate less quickly than the bi-sulphide of carbon ; he saw that it was 

 desirable to apply the insecticides in some combination which would 

 fix them and only allow them to evaporate gradually, so that their 

 action might continue long enough in any one place to infect with 

 their vapors all the surrounding soil. 



But the task of eradicating the Phylloxera has by no means been 

 accomplished by the mere discovery of the value for the purpose of 

 these substances ; there is the further difficulty of applying them to 



