374 The Principles of Fruit-growing. 
to the arsenic solution; and even then only a 
faint amber discoloration may appear, because of 
the small amount of sulfur in the water. The min- 
eral water test, therefore, is practically out of the 
question. 
This test of arsenic determines only the fact 
that soluble arsenic is or is not present. It does 
not determine how much soluble arsenic there may 
be; although the greater or less amount of the 
yellow color on precipitation will afford a compara- 
tive idea of the amount present in any two or 
more samples. 
It has already been advised to use lime with 
Paris green or London purple for the purpose of 
taking up the soluble arsenic, by the formation of 
arsenite of lime. If this is done, or if the Bor- 
deaux mixture is used with the arsenites, it will 
not mattcr if the poison contains soluble arsenic. 
11. How can one determine if Paris green is 
pure ?—It sometimes happens that material which is 
obtained as Paris green contains no arsenic. Chrome 
green may be sold instead. If the material is pure 
Paris green, it will quickly and completely dissolve 
in common strong ammonia, giving a beautiful, rich, 
dark blue, clear liquid, whilst any of the compounds 
which would ordinarily be substituted for Paris green 
on account of their color and texture, will not be- 
have in this manner in ammonia. <Any insoluble 
residue is impurity. Chrome green will not dissolve 
in ammonia. 
12. What becomes of the arsenic when it falls upon 
