6 BULLETIN 167, TJ. S. DEPABTMEXT OF AGRICULTURE. 



diehlorobenzene for 24 hours at an average temperature of 79" F. Two days later the seed was examined 

 and showed no material injury from the experiment, sprouting about as usual. 



Note. — Preliminary experiments with para-dichlorobenzene have been conducted along the following 

 lines: 1. Para-dichlorobenzene introduced into insect collection boxes for the eradication of museum pests. 

 2. Para-dichlorobenzene in combination with formaldehyde and potassium jiermanganate as an insecticide 

 and germicide. 3. Para-dichlorobenzene made into a paste by adding paraffin and resin in the presence 

 of heat, as a substitute for grafting-wax. The above paste to be applied in the burrows of borers in shade 

 trees. 4. Further experiments on the effect of para-dichlorobenzene, if any, on tender plants. 5. The 

 effects, if any, of para-dichlorobenzene on animals, when taken internally in small doses. In these experi- 

 ments green food, such as kale, cabbage, and clover, were put in a jar heavily charged with para-dichloro- 

 benzene vapors and fed twice daily to herbivorous animals, such as rabbits and guinea-pi?s. In these 

 experiments the writer has not as yet reached any definite conclusions, and therefore reserves their pub- 

 lication until further experiments along these lines are completed. 



CONCLUSION. 



From the foregoing observations and experiments the writer 

 concludes that para-dichlorobenzene, used as directed in the preceding 

 pages, acts as an excellent f umigant against the following insects : 



(1) Stored-product insects. 



(2) Case-bearing clothes moths. 



(3) Roaches and ants. 



(4) Museum pests. 



(5) Miscellaneous house insects, including flies, carpet beetles or buffalo 



moths, book lice, silverfish, mosquitoes, centipedes, and miscellaneous 

 larder insects. 



It is also an effective substitute for potassium cyanid in collecting 

 bottles. 



CHEMICAL AND PHYSICAL PROPERTIES OF PARA-DICHLOROBENZENE. 



At the request of Dr. Chittenden the following data were kindly 

 furnished by the Insecticide and Fungicide Laboratory, Miscella- 

 neous Division, Bureau of Chemistry: 



We have made an examination of the sample of diehlorobenzene submitted by you 

 for examination on December 22, 1913, and find that this product is practically pure 

 para-dichlorobenzene (C 5 H 4 C1 2 ). We have looked up some references in the litera- 

 ture in regard to this substance and give you the following information based thereon: 



Diehlorobenzene is a product derived from benzene by the replacement of two of 

 the hydrogen atoms by chlorine. There are three dichlorobenzenes, designated 

 ortho, meta, and para, the structural formulas of which are: 



,c v 



<> 



All three have the empirical formula C 6 H 4 C1 2 . Ortho and meta dichlorobenzenes 

 are liquids, the former boiling at 179° C. and the latter at 172° C. 



Beilstein, in his Handbuch der organischen Chemie, III Auflage, 1896, Band II, 

 page 44, gives three methods for the preparation of para-dichlorobenzene (in the 

 German, p-dichlorbenzol): 



