Circular 21 - Insecticides and Subsidiary Materials 27 
Diatomaceous earth is comprised chiefly 
of the siliceous remains and fragments of 
small marine animals known as diatoms. It is 
obtained as a white or light gray to pale buff 
powder insoluble in water. Industrially it is 
important in the manufacture of insulating 
materials, as a clarifying agent in making 
oils', varnishes, and drugs, and as an absorbing 
agent . 
The price of diatomaceous earth ranges 
from ^22 to $55 per ton in bags of 42, 90, 
and 120 pounds. 
For manufacturers and distributors see 
numbers 4, 32, 64, 78, and 111 of list at end 
of this circular. 
DIPHENYLAMINE 
Diphenylamine (C3_2HiiN) is applied 
directly to the wounds of animals to kill 
young screwworm larvae. 
Chemically, diphenylamine is an organic, 
colorless or white, crystalline compound of 
rather pleasant aromatic odor. It is insolu- 
ble in water but readily so in benzene. It 
is of importance in the manufacture of many 
dyes and in stabilizing explosives. 
Caution ; It should be protected from 
light, as it discolors rapidly. 
Diphenylamine is merchandised in 350 
pound barrels at 2$ cents per pound. 
?or manufacturers and distributors see 
numbers 36, 37, 39, and 66 of list at end of 
this circular. 
