364 
Messrs Purvis and Wilks, The influence 
(3) Specific gravity: 
dark = 999-49 
white = 992 ’22 
red = 992-52 
blue - 993-99 
The specific gravities show differences which are not so marked 
as in the later experiments ; and this may be due to the rise 
in temperature in the red being much more rapid than in the 
blue and the dark, owing to the absorption of the red rays ; the 
bacteria have then much less chance of active development in 
the blue and in the dark, than in the red. 
The acidities and the nitrogen contents were not determined. 
II. The following is the analysis of the unfermented wort. 
The optical activity for 100 °/ Q solution = -f 24'34°. 
The copper oxide reducing power of 20 c.c. of a 5 °/ 0 solution = 
0-222 gm Cu. 
N 
The nitrogen content ; 25 c.c. — H 2 S0 4 were used and 13 7 c.c. 
N 
of — NaHO were required to neutralise the excess after Kjeldahl- 
ing 10 c.c. of the wort. 
The wort was pitched on April 30 at 4 p.m. and as an example 
of the changes in temperature during the fermentation, the 
following table gives details of the readings. 
dark white red blue 
May 1, lOa.m 22-25° C. 22-25° C. 22-75° C. 22-00° C. 
„ 2 p.m 26-75 26-00 27-25 26-00 
May 2, 10.30 a.m.... 23-25 22-75 23-50 23-25 
„ 4 p.m 24-75 23-50 23-75 24-25 
May 3, 11 a.m 23-00 23-00 23-75 23-50 
„ 3 p.m 23-60 24-00 24-75 24-10 
May 4, 9 a.m 22-75 22-25 23-50 23-00 
The average temperatures throughout the fermentation were : 
dark - 23-8° C. 
white =23-4 „ 
red = 24-2 ,, 
blue = 23-7 „ 
The higher temperature in the red as compared with the others 
is to be noted. 
The fermentations were stopped on May 4 at 9.30 a.m. The 
one in the red and the dark had marked ethereal odours. The white 
was less so, and the blue hardly at all. The following results after 
the fermentations were obtained : 
