2 BULLETIN 1316, U. S. DEPARTMENT OF AGRICULTURE 
greenhouse and later in the field if the greenhouse experiments 
seemed to warrant it. Among the most promising chemicals so 
studied was sodium-arsenite solution. 
White arsenic, from which sodium arsenite is made, is produced in 
large quantities as a by-product from the smelting of ores of cop- 
per, silver, antimony, etc. Until recently the arsenic incidentally 
obtained by the smelting of ores for the metals was more than suffi- 
cient to supply the demand. However, with the spread of the cot- 
ton boll weevil in the Southern States and the growing use of calcium 
arsenate for the control of this pest the demand for arsenic has so 
increased that some ores are now being roasted primarily for the 
arsenic they contain. The principal sources of arsenic in the United 
States are Montana, Xevacla, and Utah, though several other West- 
ern States, such as Colorado, South Dakota, Washington, and Cali- 
fornia, have deposits of arsenic-bearing ores {29) 2 . An idea of the 
production at some of the smelters may be gained from the figures 
of Haywood {26). He states that ores received at the smelter of 
the Anaconda Copper Co., in Montana, contain from 0.51 to 2.54 per 
cent of arsenic. As this smelter has a capacity of about 10,000 tons 
daily {23) it can be seen that large quantities of arsenic are pro- 
duced, even though only from 25 to 50 per cent of it is recovered. A 
considerable quantity of white arsenic also is imported into the 
United States annually. 
Since these studies were begun in 1921 the price of arsenic has 
about doubled, owing primarily to the greatly increased use of cal- 
cium arsenate for boll- weevil control. As has been shown by Heikes 
and Loughiin {29), the consumption of calcium arsenate in the 
United States, by years, during the five-year period from 1919 to 1923, 
inclusive, was as follows (pounds) : 1919, 3,000,000; 1920, 6,000,000; 
1921, 8,000,000 ;_ 1922, 16,000,000; 1923, 31,000,000. Even at its pres- 
ent price, arsenic should be considered when a weed eradicator is be- 
ing sought. 
HISTORICAL REVIEW 
ARSENIC AS A WEED KILLER 
Railroad companies in this country and elsewhere for a number 
of years have used large quantities of sodium arsenite to destroy 
weeds along their rights of way. Also many agricultural experi- 
ment stations have advocated sodium arsenite as a weed killer. In 
Vermont Jones (&£, p. 185-186) used 1 pound of white arsenic to 2 
pounds of washing soda diluted with 3 to 9 gallons of water and 
found that this solution destroyed all weeds except a few perennial 
grasses. Pure sodium arsenite proved quicker acting at a dilution of 
1 pound in 4 to 8 gallons of water than did the preceding mixture. 
Stone {Jfl) in Massachusetts found that dilutions of 1 part of sodium 
arsenite to 20 of water, 10 gallons to a square rod, killed plants, but 
new growth soon appeared. Large trees were not injured when the 
solution was applied 2 feet around their bases to kill poison ivy 
growing there. 
Wilcox {4S, Ifl) reports that sodium arsenite in the form of a 
spray has come into general use in Hawaii to destroy weeds on rub- 
2 Serial numbers (italic) in parentheses refer to " Literature cited," at the end of this 
bulletin. 
