Mar. s, 1924 Hastening the Coloration of Lemons 759 
human beings in a few minutes. Such concentrations do not exist in 
commercial sweat rooms. 
EFFECT OF GASES DETECTED BY SPECIAL METHODS 
A stream of stove gas was bubbled through Pettenkofer tubes, some 
filled with 10 per cent potassium hydroxid solution and some with dis¬ 
tilled water. After about three days the solutions were poured out and 
the liquids were tested for various substances. 
A portion of the aqueous solution obtained in this way was tested for 
formaldehyde by the Rimini test (75, p . 85). The result was positive. 
Indeed, formaldehyde caused lemons to turn yellow, but the color was 
too brassy, and sunken spots formed in the rind wherever drops of vapor 
condensed. A similar result was obtained with acetaldehyde. 
The solution of potassium hydroxid through which the stove gas had 
bubbled was tested for nitric oxid by the method described by Dennis 
(5, p. 218). A distinctly positive test was given. Nitric oxid, gen¬ 
erated from sheet copper, potassium nitrate, and concentrated sulphuric 
acid were applied to green lemons in desiccators. None of the lemons 
turned yellow, but some of them showed surface injuries. 
The water and potassium hydroxid absorptions were also tested for the 
presence of phenols by Scott’s method ( 16 ). A positive test was ob¬ 
tained. The vapor from phenol turned green lemons yellow in about 
six days and no blemishes were caused. However, it did not seem 
possible to make any practical application of this fact. 
Stove gas was bubbled through Pettenkofer tubes containing solutions 
of ammoniacal and of neutral silver nitrate. A small quantity of a pre¬ 
cipitate, probably silver acetylide, was formed. On adding acid, this 
decomposed, giving off a gas with an odor of acetylene. Acetylene 
from a commercial cylinder at a concentration of 1 to 1,000 was effective 
in bringing about coloration. Since commercial acetylene is said to con¬ 
tain traces of other gases, however, acetylene of greater purity was pre¬ 
pared by treating ethylene dibromid with alcoholic potash {14, p. 84 ). 
The gas generated in this way caused no change in the coloration of lemons 
after exposure for seven days to concentrations of 1 to 100, 1 to 1,000, 
and 1 to 50,000. Hence the coloration obtained by the use of com¬ 
mercial acetylene is thought to have been caused by the impurities 
present and not by the acetylene itself. 
REMOVAL OF EFFECTIVE CONSTITUENT FROM STOVE GAS BY 
ABSORBENTS 
Since the effective constituent seemed to be present in the stove gas 
in low concentrations only, an effort was made to absorb this trace by 
reagents. In the apparatus devised for this work (fig. 1), a current of gas 
from the stove was drawn through the system by reduced pressure at S 9 
the reduction being equivalent to about 7 inches of water below atmos¬ 
pheric. By a stopcock at C, bubbles from 3 to 4 mm. in diameter were 
made to follow one another in rapid succession up the tube in which 
they were washed by the absorbing liquid. From 7 to 10 seconds were 
required for a bubble to travel the length of the tube. 
It can not be stated that complete absorption took place, since, for 
the complete removal of a gas by a liquid, shaking for several min¬ 
utes is often recommended. When solid-absorbing reagents were used 
