384 STUDIES ON FERMENTATION. 



with a 6-litre flask containing about 4 litres (7-04 pints) of beer 

 that had been in " low " fermentation from February Srd. The 

 beer was cleansed on February 24th, and had a density of 5|° 

 Balling. We collected 2'345 kilos (75'39 oz. troy) of yeast, 

 containing 56 per cent., that is, 1*313 kilos (42"21 oz. troy) of 

 pressed yeast, containing 36-7 per cent, of yeast dried at 100° C. 

 (212° F.), that is 482 grammes (15-49 oz. troy) for the brew, 

 which would give 241 grammes (7*748 oz. troy) of yeast formed 

 per hectolitre (22 gallons). 



The beer was turbid when drawn off, and the small glassful 

 that we removed did not brighten in twenty-four or even forty- 

 eight hours. The samples for some days previously had been 

 in the same condition. The yeast existed as a fine deposit 

 without any straggling yeast about the sides. The want of 

 brightness was dependent rather on spurious colour than on 

 any actual turbidity. "We may here remark that if in the 

 preceding experiment the wort had taken up oxygen into com- 

 bination as well as into solution at the time that it was aerated, 

 the other conditions being the same, the beer would have 

 been bright and better. 



It follows from this experiment that a wort may be perfecthj 

 bright at the moment when it is pitched, yet fail to produce a 

 beer which shall be bright when racked, or one that will brighten 

 subsequently otherwise than with great difficult3^ We may 

 add that when we repeated this same experiment, cooling the 

 wort, however, as rapidly as the conditions of our apparatus 

 permitted, and employing iced water, the beer appeared very 

 nearly bright when it was racked, and brightened pretty quickly 

 in cask and in bottle. The total duration of cooling was not 

 longer than two hours. 



The question here arises what part does the oxygen combined 

 with wort play in the clarification of the latter, or in the clari- 

 fication of beer ? Although it may be difficult to give a definite 

 answer to this question, we must bear in mind that in cases 

 where the beer brightens best, if we examine it under the 

 microscope during fermentation, M'e see, besides the clusters of 



