364 STUDIES ON FERMENTATION. 



The definitive formula, therefore, is : 



(1) ^=1-16 + (B-15) 0-022-(/;-15) 0-006, 

 or again, 



(2) - =0-86-(B-15) 0-016+ (^-15) 0-004. 



The coefficient c of the solubility of oxygen in water will be 

 found in the table given a few pages back. 



§ III. — On the Quantity of Oxygen existing in a state 

 OF Solution in Brewers' Worts.* 



The wort, when it comes from the copper in which it is 

 boiled with the hops, remains exposed upon the coolers for a 

 time, the length of which varies according to circumstances, 

 the most important of which is the exterior temperature. The 

 average time is from, seven to eight hours, during which the 

 volume of the wort diminishes, whilst its density increases ; at 

 the same time, it deposits its proteinaceous matters and absorbs 

 oxygen from the air, either by way of solution or of combination. 



In the present paragraph we shall confine ourselves to the 

 uncombined oxygen held in a state of solution in Avort, recog- 

 nizable by the change of colour produced by its action on M'hite 

 indigo. 



The use of the coolers enables the brewer to obtain his wort in 

 two distinct states of limpidity — filtered wort and unfiltered 

 wort. At the same time there is a further difference between 

 these worts, namely, in the quantity of oxygen held in solution. 

 The unfiltered wort comes direct from the coolers ; the wort to 

 be filtered, mixed with a part of the deposit, is run into a 

 special vessel, from which it is distributed over the filtering 

 surfaces, which are generally of felt ; filtered bright, it is then 

 received in a reservoir, from which it is distributed amongst 

 special fermenting vessels. Falling through the air in a thin 

 stream of drops, it must necessarily have become charged with 



• Experiments made, at our request, by MM. Calmettes and Oreuet, at 

 Tantonville, in Tourtel's brewery. 



