356 ON THE LACTIC FERMENTATION 
or any higher degree short of about 350° has been continued for two hours, 
the gas is turned off and cooling is allowed to take place ; and when the apparatus 
is quite cool, the covered glasses may be removed with confidence that they are 
perfectly free from living organisms. 
In the next place, how shall any pure organic liquid be introduced into one 
of these purified liqueur-glasses without risk of contamination? This we are 
now able to manage in a comparatively simple manner. The liquid is intro- 
duced by means of a flask of this form (N), having a bent spout, large at the 
commencement and comparatively 
narrow in its shorter terminal part 
(O) beyond the bend. The large size 
of the first part of the spout prevents 
it from ever acting like a syphon ; 
and the result is that, when liquid 
is poured from such a flask and the 
vessel is afterwards restored to the 
erect position, the end of the nozzle 
remains valved by a drop of the 
liquid ; and this guards the orifice, 
so that regurgitation of air can 
never take place through the nozzle. 
And the mouth of the flask being 
covered with pure cotton-wool (P), 
the air that enters the flask during 
the pouring out of the liquid is fil- 
Fic. 4. tered of its dust by passing through 
the cotton. When the decantation 
is completed, a piece of rag wrung out of a strong watery solution of carbolic 
acid (I to 20) is applied to the orifice of the nozzle, and, by capillary attraction, 
sucks out the drop; after which a cap of carbolized cotton-wool (Z in 
Fig. 6, p. 360) is tied securely over the nozzle, the ligature obtaining a pur- 
chase upon the projection (O) upon the tube.t. When this has been done, the 
liquid, if it was pure to start with, and the flask also pure, will remain 
* Cotton-wool intended for a cap to cover the mouth or nozzle of a flask is conveniently applied 
between two pieces of open muslin, which ensure that the cotton shall remain as a uniform layer, and 
also permit it to be readily removed without leaving any of the cotton adhering to the glass. The best 
material for the ligature I have found to be very fine iron wire, tied firmly in a half knot, which is 
secured by giving the ends of the wire a bend, so as to convert them into hooks. <A good mode of car- 
bolizing the cotton-wool is to treat it with a solution of 1 part of carbolic acid in 100 parts of anhydrous 
sulphuric ether. The cotton greedily imbibes the liquid into all its parts and the ether evaporating 
leaves the carbolic acid behind in the cotton, which is thus rendered highly pungent and antiseptic. 
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