Arsenic in the Soil. 375 



the soilf With the action of the rains and the fall- 

 ing of the leaves, most of the arsenic which is 

 applied to trees finally reaches the soil. What then 

 becomes of it? If lime has been used with the 

 spray, the arsenic will be insoluble when it falls 

 upon the soil. It is possible that the organic acids 

 in the soil, and also carbonic acid, may dissolve some 

 of the arsenic, but it would be almost surely made 

 immediately insoluble again by combination with lime 

 or other soil constituents. If soluble arsenic is placed 

 on the soil, it probably almost immediately goes into 

 insoluble combinations, and remains where it was 

 placed unless slightly washed down by mere mechan- 

 ical means. Now, some plants appear to have the 

 power to take up very minute quantities of arsenic 

 and still thrive probably so minute that the nicest 

 chemical test can scarcely discover it, but any appre- 

 ciable quantity of soluble arsenic in the soil quickly 

 destroys the roots. If, therefore, the grass and other 

 plants under sprayed trees continue to live, there 

 need be no fear that the arsenic will injure the soil. 

 A study of the destination of arsenic which has 

 been applied to the soil in the form of Paris green 

 was made at the Cornell Station (Bulletin 101), from 

 which the following conclusions were drawn: "The 

 gist of the whole matter then, if we may generalize 

 from these tests, is that the arsenites do not leach 

 from the soil. They remain where they fall, the 

 same as sand does, and are carried down only when 

 there are crevices or other openings in the soil, and 

 they then go down as insoluble compounds, and to 



