IMPURITIES IN PARIS GREEN. 395 


three-quarters of an acre. The average daily gain from Lot 1 
was 1°27 Ibs. and 1°22 lbs. from Lot 2. From the results of 
the experiment, which have been carried out for two years 
in succession, it is*concluded that farmers feeding a large 
number of pigs cannot provide a better pasture for their sows 
and young pigs than by sowing small plots of rape at succes- 
sive periods about three weeks apart during the spring and 
early summer. : 
Inquiries have been conducted, both by the Californian and 
by the New York Experiment Stations 
Impurities in in reference to some complaints as to 
ParisGreen. the unreliability of Paris Green as an 
| insecticide, and the conclusions arrived 
at were reported in a recent number of the United States 
Experiment Station Record. Paris Green, it is stated, 
proved satisfactory when a standard quality was used, and 
its unreliability appeared to arise from adulteration ; for 
instance, it was found that white powders, such as gypsum 
or flour, had sometimes been added to increase the weight, 
whilst in Paris Green of low quality there was a considerable 
percentage of free or arsenious oxide, which was injurious to 
foliage, and which rendered the substance dangerous and 
worthless as an insecticide. The standard recommended by | 
the Californian Station requires that the sample shall only 
show a trace of foreign matter under the microscope ; that the 
total combined non-soluble arsenious oxide shall exceed 50 
per cent.; and that the sample shall contain practically no 
free arsenic or other soluble arsenical compound. The 
addition of lime to the water in which Paris Green is mixed 
was found to render insoluble the free arsenic which was 
present, in cases where the quantity of this substance was not 
large. 

