a DEHYDRATION OF FRUITS AND VEGETABLES 29 
Bulletin 872 (28) and in Farmers’ Bulletin 699 (38). Theimportance 
_ of killing insectsin stemmer trash by hydrocyanic-acid gas is discussed 
by Hamlin and Benton (35). Hydrocyanic-acid gas is a most 
dangerous gas and should be used only by careful, thoroughly in- 
formed persons. One deep breath of the concentrated gas has been 
known to cause instant death. 
CARBON DISULPHIDE 
Carbon disulphide is an excellent fumigant for dried fruits whenever 
it can be used safely. The gas is explosive and inflammable in the 
presence of fire from any source, whether it be a lighted match, the 
spark caused by striking a nail, or the spark from an electric switch. 
It is used for fumigating under ordinary conditions and also in vacuum 
outfits. Because it isagas heavier than air it can be depended upon for 
better penetration than hydrocyanic-acid gas, provided it is used in a 
tight container. Excellent results can not be obtained unless the mate- 
rial treated is fumigated in a very tight container. Because of its 
inflammable and explosive nature it is not recommended for the 
fumigation of large plants as single units. Information regarding 
- carbon disulphide and its use as a fumigant is given in Farmers’ Bulletin 
799 (36). 
CARBON TETRACHLORIDE 
Carbon tetrachloride (29, 57) upon evaporation forms a gas that is 
heavier than air. In this and in its power of penetration it resembles 
closely the gas of carbon disulphide. Stocks are fumigated with it in 
the same manner as when carbon disulphide is used. It has an advan- 
tage over carbon disulphide in that the gas is noninflammable and non- 
explosive. In fact itis a standard fire extinguisher. It has, however, 
the great disadvantage of being about one-fourth to one-half as 
effective as carbon disulphide when equal quantities of the liquid of the 
two gases are used. It is also less reliable, in that results following 
its use are less dependable. As it costs about the same as carbon 
disulphide per pound, fumigation with it is more expensive than with 
carbon disulphide. 
CONTROL BY HEAT 
A dry heat ranging from 125° to 130° F., applied for several hours, 
will kill all insects attacking dried fruits, provided they are actually sub- 
jected to this temperature. Moist heat apparently is not so effective. 
No data bearing directly upon the use of heat in dried-fruit establish- 
ments were available in January, 1925. The subject of heat control 
is under investigation in the Bureau of Entomology. The installa- 
tion of piping or other equipment sufficient to heat a plant to 125° 
to 130° F. is probably in the long run the cheapest and best method 
of controlling insects in the manufacturing plant itself. The value 
of heat for controlling insects in the fruit must be studied further 
before definite recommendations can be given. 
PACKING AND STORING 
| For convenience in handling and to facilitate the application of 
_ heat cr fumigation, products should be packed in the room where 
they were cured and stored. \ Such a room should be strictly clean, 
