9 
of this substance shows that besides combined arsenious acid and 
oxide of copper it contains— 
Per cent. 
Free arsenious acid (when extracted with sodium BORG) 2 e cava cae 3.20 
Free arsenious acid (when extracted with cold WHET) 0c scct eee wcek 5. 88 
pomnit Sip hates ssc.semctac sss boeeucekde cu an ceduscaccedsecsesecd 2. 02 
PP Rae daunted aa cule acman Shin ddnmmaniniead Uemia weeanecwic soScas 1.30 
It will at once be seen that the percentage of free arsenious acid is 
somewhat too high when a water extraction is used. The amount of 
sodium sulphate and sand present also is too large, causing the manu- 
facturers to gain the price of over 3 pounds of Paris green on each 
100 pounds sold, with an equal loss to the consumer if the price is 
maintained.’ We would not, of course, expect to have commercial 
articles entirely free of these two substances, but with care the sodium 
sulphate could easily be reduced to 1 per cent, and the sand to much 
less than 1 per cent. As a whole, however, this is a very good 
compound and has given excellent results in the various State stations, 
especially when mixed with a little lime. 
“ PARAGRENE.” 
The second substance spoken of above is a patented article “* Para- 
grene.” This is composed of arsenious acid, oxide of copper, acetic 
acid, and about 27 per cent gypsum. The gypsum, of course, is of no 
use as an Insecticide, so is in the way and only adds weight. Also 6.12 
per cent of the arsenious acid is present in a soluble condition. 
Consequently this can not be classed as a high-grade insecticide. 
LONDON PURPLE. 
London purple is another of the arsenical insecticides sold in 
America in large quantities. This substance is prepared by boiling a 
purple residue from the dye industry, containing free arsenious acid, 
with slaked lime. In this way a compound of these two substances, 
called calcium arsenite, is formed. This on exposure to the air during 
subsequent boiling is partly converted to a closely allied compound, 
calcium arsenate. Since the dye residue has accumulated some dirt 
during the process of manufacture, sand will also be present in all 
samples of London purple. It will thus be seen that this substance 
will consist of calcium arsenite, calcium arsenate, a dye residue, and 
small amounts of sand and moisture. In case not enough lime is 
added to the dye residue or the boiling is not continued long enough, 
some of the arsenious acid will be present in the free condition, thus 
causing the foliage to be scorched. 
A chemical examination of four samples, recent] y made by the author, 
shows that the moisture varied from 1.87 to 4.07 per cent, the sand 
from 2.46 to 3.55 per cent, the arsenious acid from 6.40 to 17.31 per 
