FUMIGATION AGAINST GRAIN WEEVILS 3 
have been only stupefied.) To obtain the desired humidity, air 
was bubbled through bottles of sulphuric acid of the proper density, 
the vapor pressure of water in sulphuric acid-water mixtures being 
known for mixtures of various densities. In the less volatile com- 
pounds, the quantity of the compound present in the jar in the form 
of vapor was determined by passing a known volume of air over a 
weighed quantity of the compound. The loss in weight (in grams) of the 
compound divided by the quantity of air (in liters) gives the quantity 
(in grams) of substance present in the form of vapor per liter of air. 
The following factors were used in calculating ae results reported: 
Grams per liter X 62.43=pounds per 1,000 cubic feet. 
22.4 < 100 
gram-molecular weight 
Percentage concentration X gram-molecular weight X 0.02787=pounds per 
1,000 cubic feet. 
1 cubic foot = 28.32 liters. 
1 kilogram = 2.20462 pounds. 
Assuming the vapor of a compound to be a perfect gas, the mole- 
cular weight (in grams) of this vaporized compound will occupy 22.4 
liters under a pressure of 760 millimeters of mercury and at a tem- 
perature of 0° C. For example, the molecular weight of chloroform 
is approximately 119.4. Therefore, if 22.4 liters of space contains 
119.4 grams of chloroform vapor (equivalent to 5.33 grams per liter), 
the percentage concentration is 100. 
Since the tests were made at about the same temperature on com- 
pounds differing greatly in vapor pressure, it follows that the more 
volatile compounds were tested in high molar concentrations and 
the slightly volatile compounds were tested in low molar concen- 
trations, which, however, were the maximum concentrations of the 
vapors possible at the temperature of the test. 
Grams per liter x =percentage concentration. 
EFFECT OF VOLATILE ORGANIC COMPOUNDS ON WEEVILS 
The results of the fumigation of weevils in glass flasks at room 
temperature (21° to 32° C.) are shown in Table 1. Table 2 gives 
the formula, molecular weight, boiling point, and minimun lethal 
concentration for each compound tested. 
~TasiE 1.—Results of fumigation tests on weevils in glass flasks at room temperature 
(21° to 32° C.) 
Concentration Weevils killed after exposure 
of fumigant for 24 hours 
Tem = Se aes 
Test No. pera- Fumigant Molar | Pounds Ss ao 
ure per per ribo- 
cent- | 1,000 | oryza rae lium | Plodia 
age cu. ft. 
HYDROCARBONS: XC, P= ct IPS cr PS ch) Peet 
RS se ok So 25 0eeAIMYlONe! 22 2 - es AEST 78. 76 100 100 LOOM eases 2 
Ag ee sen ae Ag ee (Oe ee 14.73 | 28.78 0 0 Oi peek 2 
5 7 ae ern 22- hel taaes Gore Se a. Se 21.26] 41.54 0 0 Qzls sere Set 
Ly ee eee Ja De. Sule eerosene: =. — Soa. 2. 1.40 1. 43 0 0 0 10 
eee re 23. 0 | Cyclohexane--__-.--------- 13.00} 30.48 100 100 100 85 
aI ee ea 30: by (Eee oa ee a 14. 00 32. 82 100 100 100 70 
See eee 23057 |eBenzenes = 1 sot 1. 13.00} 28. 100 100 100 100 
ASO oS st 72st) joe ee Oe RR EAE 8 . 90 1. 96 0 0 0 0 
eet saree SE 1 ee Gta Se Be ee 1.60 3. 48 10 30 80 0 
ASG 242 Ee S05 Sr |en— GOS wre 8 ie A 3. 80 8. 27 100 100 100 70 
Sie hs a 285 le Polmence 2 eS se 3. 00 7.70 75 50 100 80 
75 oe nate f 3030) fo xylene. 3°96 e_ ts 1. 40 4.14 60 0 Orpen 
1 YG 2 ee 24.0 | Naphthalene (25 per cent) 2.50 1.79 75 207 jescnsehe 25 
and carbon tetrachlo- 
ride (75 per cent). 
RU ote) Sere 23 Se eAnthracene 8) 9) ant SOI; .05 | 0 0 0 0 
1 Molecular weight of kerosene assumed to be 128. 2 Concentration of naphthalene only. 
