AMERICAN 
JOURNAL OF BOTANY 
Vol. IX June, 1922 No. 6 
COMPARATIVE STUDIES ON RESPIRATION XXI. 
ACID FORMATION AND DECREASED PRODUCTION OF CO2 
DUE TO ETHYL ALCOHOL 
Marian Irwin and Margaret Weinstein 
(Received for publication October i, 1921) 
The purpose of the present investigation is to determine the effect of 
ethyl alcohol on the production of carbon dioxide by seedhngs of the radish 
(Early French Breakfast). 
The seeds were allowed to germinate on moist filter paper until the 
caulicles were about 5 mm. long: they were then used for the experiments. 
The apparatus used for the determination of carbon dioxide production is 
described in a previous paper. ^ It is important first to test the apparatus 
for leakage and to allow the air to pass through the tube containing the 
lumps of sodium hydroxide until the whole apparatus is practically free 
from carbon dioxide. The tube is then disconnected and the organisms 
are placed in it. It is important that a check experiment, without the seed- 
lings, should be made to ascertain whether the entrance of the laboratory 
air on disconnecting the tube introduces any error. After the seedlings are 
placed in the tube and the whole apparatus is again connected, the air is 
again pumped through a tube containing sodium hydroxide for three min- 
utes to absorb the carbon dioxide which is introduced when the tube is 
disconnected. 
The period during which the liquid containing the indicator changes 
from pH 8 to pH 7.6 is recorded by a stop watch, and the reciprocal of 
this time is taken as the rate of production of carbon dioxide by the seed- 
lings. 
The color of the indicator is affected by alcohol, which makes it neces- 
sary to correct the readings by calibrating the indicator solutions which 
have taken up alcohol vapor by adding to them measured amounts of car- 
bon dioxide. This must be done for each concentration of alcohol. 
In order to ascertain the normal rate of respiration, seedlings are placed 
in tap water and readings are taken every ten minutes for three hours. 
Curve A, figure i, shows that a series of readings of this sort agree, and it 
is evident that the experimental errors are not large. An average of the 
^ Irwin, M. Jour. Gen. Physiol. 3 : 203-206. 1920. 
[The Journal for May (9: 213-276) was issued June 21, 1922] 
277 
