370 
Messrs Parvis and Wilks, The influence 
C. 
In this series of experiments, four were conducted in un- 
sterilised glass vessels and two in unsterilised copper vessels, 
using only red and white light for the latter. The optical activity 
of a 100 °l solution was about + 16°. 
The average temperatures 
June 3 at 9 a.m. were : 
I. Glass vessels 
dark = 2T4° C. 
white = 22 - 3 ,, 
red = 22 - 3 „ 
blue =21-3 „ 
The values of the optical 
were : 
I. Glass vessels 
dark = + 3 ‘42° 
white = + 3 '48 
red = + 3*36 
blue = + 3 - 43 
between May 30 at 10.30 a.m. and 
II. Copper vessels 
white - 22-3° C. 
red =22-0 ,, 
activities after the fermentations 
II. Copper vessels 
white = + 4‘94° 
red = + 7'61 
The numbers obtained from the fermentations in the glass 
vessels do not show very great differences, whereas those obtained 
from the copper vessels are very marked. The great difference 
between the numbers obtained from the copper vessels compared 
with those of the glass vessels is also very noticeable. 
The values of the acidities after fermentation were the following; 
N 
the numbers represent the amount of alkali required to neutralise 
the acid produced : 
I. Glass vessels II. Copper vessels 
dark =12 , 3c,c. white = 57’4 c.c. 
white =12-5 „ red = 8T3 „ 
red = 13 ’3 „ 
blue = 23 - 8 „ 
The fermentation in the blue light can hardly be compared 
with the others because the temperature was very low (only about 
19°) for a long time, and this probably affected the vitality of the 
yeast, so that bacterial action became stronger. The numbers 
obtained from the copper vessels were also very high, and may be 
explained by the fact that the wort had remained corked up in 
a bottle for a day ; and, although, from the smell, there was 
no apparent acidification, it is probable there was a development 
of acid producing bacteria. The acid would dissolve a little of the 
copper, and thereby retard the action of the yeast. 
