Materials and Formulas. 125 



Paris Purple. This substance closely resembles English 

 purple poison, being of a very deep maroon color. Chemical 

 analysis shows 34.1 per cent of arsenic trioxide, 40.7 per cent of 

 this amount being soluble in water. It may be used in the 

 same manner as recommended for English purple poison, and 

 it is also defective from the fact that it does not mix readily 

 with water. 



BENZINE. Benzine has been used in the place of the 

 bisulphide of carbon for the destruction of insects infesting 

 seeds. It is not so energetic as the latter, so that larger quan- 

 tities of the liquid must be used. 



BISULPHIDE OF CARBON. See CARBON BISULPHIDE. 



BLIGHT POWDER. See SULPHATED SULPHUR. 



BLUE STONE. See COPPER SULPHATE. 



BLUE VITRIOL. See COPPER SULPHATE. 



BORAX. Borax, whether used as a powder or in a strong 

 solution, is of value in driving roaches and similar vermin from 

 the places they frequent. 



BORDEAUX MIXTURE ; COPPER MIXTURE OF GIRONDE ; 

 COPPER SULPHATE AND LIME MIXTURE ; MILLARDET MIX- 

 TURE. The early history of this fungicide has already been 

 thoroughly discussed, as well as the first formulas adopted for 

 its manufacture. The chemical composition of the mixture is 

 by no means clear, for although at first thought it would 

 seem that the reactions which take place when the copper 

 sulphate solution and the milk of lime are brought in con- 

 tact with each other must be quite simple, still such is not the 

 case. The new compounds formed vary with the proportion of 

 the ingredients, and all who have observed the behavior of the 

 mixture must have noticed that it varies in color with the dif- 

 ferent amounts of lime added, sometimes being intensely blue, 

 again, much paler blue; and frequently a greenish tinge will be 

 noticed, this being most marked when a small amount of lime 

 is present. Since the chemistry of the mixture has not yet 

 been accurately determined, it will be of little avail to discuss 

 the various theories regarding its composition, and only those 

 concerning which there is the most certainty may here be briefly 

 mentioned. 



When the mixture was first studied, it was supposed that the 

 union of the two ingredients caused the formation of copper 



