6 BULLETIN 1367, U. S. DEPARTMENT OF AGRICULTURE 
out the excessive heat which was yielded by complete combustion 
of the kerosene, though of course considerable heat is necessarily 
generated. in this process. The method followed in modifying this 
burner can be adapted to other burners of different construction, for 
the principle involved is the same. The air supply should be cut 
down just as much as possible while still vaporizing the kerosene, so 
that the flame will be blue. If the draft is cut off too much the 
burner will smoke, flare up, and give off quantities of soot, resulting 
in a dirty appearance of the fruit without producing the desired 
orange or yellow color. The gas formed in this way is frequently 
called “ stove gas,” and this term will be used in this bulletin. 
RELATION OF TEMPERATURE TO RATE OF COLORING 
The temperature at which the fruit is held has a very important 
bearing upon the rate at which the fruit colors and also upon the 
appearance, keeping quality, and general condition of the colored 
fruit. If the temperature is high the fruit is liable to become brown 
or scalded in spots, or it may be so severely injured that its life 
after it is removed from the coloring room is very short. It was 
observed early in the work in Florida that the presence of the stove 
in the room with the fruit had a tendency to produce dangerously 
high temperatures. Air temperatures as high as.120° F. were found 
in numerous instances in boxes of fruit near the stove. This tem- 
perature is, of course, too high and undoubtedly is harmful to the 
fruit if maintained for any considerable period. 
Experiments were made to determine the rate at which the fruit 
would color at temperatures under 90° F., which is considered about 
as high a temperature as it is safe to use. Fruit was cooled down 
and colored in a precooling plant, the stove being placed directly in 
the room with the fruit and sufficient refrigeration furnished to take 
up the heat from the stove and cool down the fruit at the same time. 
Inasmuch as this experiment was carried on with carload lots, it 
was not possible in every case to get exactly comparable fruit. The 
results, however, are so marked as to eliminate any error from this 
variation. In these experiments the temperature of the fruit as it 
was placed in the room was taken by means of thermometers thrust 
into the fruit, and temperature determinations were made in this 
way at intervals during the process. 
EHaperiment 1—Parson Brown oranges at a temperature of 80° F. 
were placed in a precooling room, cooled down to a fruit temperature 
of 40° in 48 hours, and held at that temperature until they were 
about 50 per cent colored, gas being applied continuously. It re- 
quired six days to color this fruit. 
Eaperiment 2.—Parson Brown oranges at a temperature of 80° F. | 
were subjected to gas from a kerosene stove for 24 hours at 80°, at | 
the end of which time the fruit began to show a tinge of yellow color. 
Refrigeration was then turned on and the fruit cooled and treated 
with gas at the same time. At the end of four days it was well 
colored. 
Heperiment 3—Pineapple oranges showing 20 per cent color and 
having a fruit temperature of 90° F. were placed in a coloring room 
having an air temperature of 56°. The fruit reached a temperature 
of 64° F. in 24 hours and was maintained at 62° to 64° for the next 
