4 BULLETIN 1367, U. S. DEPARTMENT OF AGRICULTURE 
In the second experiment the room was filled with grapefruit 
which showed about the same percentage of color as the first lot, 
and the same plan of intermittent gas treatment and ventilating 
was followed as before. At the end of 29 hours, the gas having 
been applied for 19 hours of this time, the fruit was approximately 
50 per cent colored. The engine was then stopped and the fruit 
held in the closed gas room 38 hours longer. At the end of this 
time the fruit was from 90 to 100 per cent colored and in practically 
the same condition as that in the first run. The lot which received 
the most gas reached this same color condition in 21 hours less time. 
The third experiment was made with a mixed lot of sorted fruit, 
the entirely green being separated from the turning fruit or that 
showing 5 to 10 per cent color. The same procedure of intermittent 
gas treatment was followed in this as in the two earlier experiments. 
After 73 hours in the coloring room, with the engine running 31 
hours of this time, the turning fruit was from 90 per cent to full 
color, and the fruit which was deep green when placed in the 
room was just beginning to take on a yellowish tinge. This last- 
mentioned lot of fruit was kept in the coloring room with inter- 
mittent gassing for 66 hours more, or about six days in all, at the 
end of which time it was about 90 per cent colored. This experi- 
ment demonstrated that it was possible to color even deep-green 
grapefruit but that it required a considerably longer time than that 
which was changing color naturally. 
In the fourth experiment, a roomful of grapefruit showing 5 to 
10 per cent color, as in the first two experiments, was used to test © 
the effect of a very light concentration of the gas. The gas was 
applied for a period of 4 hours on both the first and second days 
and for 11 hours the third day. The engine was then stopped 
and the room kept closed. At the end of 50 hours the fruit was 
about 70 per cent colored, and in 39 hours more, or 89 hours in all, 
it was practically full colored. The buttons (short ends of stems 
with the calyx lobes attached) were still firm and green, in contrast 
to the results obtained in the first three experiments, in which they 
were loosened during the gas treatment and in many cases dropped 
out. 
These four experiments demonstrated that it was possible to color 
early grapefruit with exhaust gases from a gasoline engine and that 
a good color is obtained by intermittent applications of the gas. 
This of course tended to give a lower concentration of the gas, with 
the result that the buttons remained on the fruit. The results of 
these experiments were applied on a larger scale in another coloring 
room of nearly a car capacity. In this room 300 boxes of Davis 
grapefruit were colored in about 72 hours by the exhaust from a 5- 
horsepower engine, the gas being applied about 13 hours each day. 
The fruit was well colored at the end of three days, and most of the 
buttons remained attached to the fruit after brushing. The grape- — 
fruit was in good condition when marketed. These experiments show 
that fruit can be colored by the exhaust from a gasoline engine and 
that in some cases at least this procedure would be commercially 
practicable. It of course involves the operation of an engine, which 
in most cases would run idle part of the time. 
