GUI/TUBE FLASK, 



apparatus. A small funnel-shaped opening permits the ga> to <- -apr 

 during fermentation. 



This ventilating apparatus not only permits the gas i e>cape. hut 

 makes it possible to observe the activities going ,, n \\ithin the (I;isk 

 and also protects the meiliuin from contaminat ion by air. The gro \vtli 

 of the yeast is noted by the rate of passage of gas through the con- 

 trol liquid, which should be 5 to 10 per cent sulphuric acid. This de- 

 vice, when the control liquid is in place, makes it impossible for germs 

 to enter if, by change of temperature, air should be drawn into 

 the bottle or flask. It also 

 renders evaporation of the ttcml 



culture medium impossible 

 to any appreciable degree 

 during the short period of 

 the test. \ 



The stopper carrying the 

 control apparatus is fixed 

 in the bottle or flask after 

 the measured, or preferably 

 weighed, quantity of cul- 

 ture medium has been 

 placed in it, and the neck 

 of the bottle or flask, in- 

 cluding the cork, is closely 

 wrapped with parchment 

 paper held in place by a 

 rubber band. The outer 

 funnel opening is plugged 

 with cotton. The whole 

 apparatus, with its con- 

 tents, is then sterilized by 

 steam heat and set away, 

 ready to be sown with the 

 organism to be tested. For 

 acid fruit juice one steril- 



ization, heating for forty FlG " 2 - DetaiI ot wntllatton tl 

 minutes in steam at 100 C., is sufficient, but for malt or like nih- 

 stances this should be repeated on two successive days. 



Whe'n making this test, it is of the greatest importance to sow under 

 conditions which, as far as possible, prevent the entrance of extranet Mi- 

 organisms. It is also important to sow all cultures with a standard 

 loop of platinum wire prepared to carry a drop of uniform si/< . 

 Otherwise, tests made at different times in the laboratory may show a 

 different rate of fermentation at inception, not by reason of greater or 

 less activity on the part of the yeast used, but because of the greater 



J..1 



0.75 



