Ciroular 21 - Insecticides and Subsidiary Materials 76 
Sulfuric acid is available on contract: 
see Class 51, General Schedule of Supplies, 
Procurement Division, Treasury Department. 
TALC OR TALCm^ 
Talc or talcum is a suitable material 
for mixing v;ith derris powder for the control 
of fleas on cats. For limited use of this 
kind, ordinary cheap talcmii powder is satis- 
factory, while if large quantities are required, 
talc as manufactured for preparing insecticid9.1 
dusts should be employed. Talc of insecticidal 
dust grade is used to make a paris green dust 
for the control of mosquito larvae. 
Talcum, talc, or soapstone occurs in 
the native mineral state as a magnesium sili- 
cate, H2Mg3(Si03); . It has a soft, soapy feel 
and occurs in layers, granules, or fibrous 
masses usually of a grayish, or greenish color. 
In addition to its usefulness in preparing 
insecticidal dusts, it is employed in making 
soap, paper, paints, insulating materials, 
textiles, and toilet powders. 
The material (325 mesh) is obtainable 
in 100, 200, and 220 pound bags in carload 
lots at $1U to $20 per ton. 
Available on contract: See olass 51, 
General Schedule of Supplies, Procurement 
Division, Treasury Department. 
