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 arsenit.es, it will 

 not matter if the poison contains soluble arsenic. 



11. Ho ic can one determine if Pa rift green is 

 pure f 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 ftilh upon 



