of light and of copper on fermentation. 
369 
alkali used to neutralise 50 c.c. of each fermentation: 
dark = 20-85 c.c. 
white = 23 -80 „ 
red = 13 - 60 „ 
blue =12-05 „ 
white (in glass beaker) = 12-90 „ 
The great diminution in the acidity when the fermentation 
was carried on in the glass vessel compared with the corresponding 
experiment in the copper vessel, and under the influence of white 
light, is noticeable. 
B. 
In the second series of experiments, the fermentations were 
carried on in sterilised glass vessels, and the fermenting solutions 
were not of ordinary hopped wort, but contained : 
10 -00 °/ o glucose 
0-15 °/ o ammonium sulphate 
0-15 °/ o ammonium phosphate 
Of this solution 150 c.c. were used in I. series of experiments, and 
the same volume diluted to about one half the strength in the 
II. series of experiments. The experiment marked I A was 
conducted in a non-sterilised glass vessel open to the air, and the 
result showed that the carbon dioxide could easily escape from 
the other vessels, so that there was nothing to be feared from its 
action. The other glass vessels were loosely covered with glass 
wool, through which thermometers passed into the fermenting 
wort. The light was filtered through red glass plates for the red 
rays and through ammoniacal copper solutions for the blue rays, 
and the effect was compared with the direct effect of white light 
and with one guarded from contact with any light by the vessel 
being covered with black cloth. Pure cultures of S. Cerevisise I. 
were used to ferment the nutrient solutions. 
The optical activity of 100 °/ 0 of the original solutions was 
= + 10 01°. The average temperatures of the series of fermenta- 
tions between May 28 at 11 a.m. and June 3 at 9 a.m., were: 
I. dark =23-7° C. 
white =23-3 „ 
red =23-7 „ 
blue = 23-3 ,, 
II. 23-3° C. 
23-6 „ 
23-7 „ 
22-9 „ 
I a. 22-9° C. 
After the fermentations, the following numbers were obtained 
for the optical activities : 
I. dark = + 2‘34° 
white = + 2 -3 5 
red = + 2-28 
blue =+2-35 
II. +1-85° I a. +2-35° 
+ 1-82 
+ 1-81 
+ 1-81 
