FERMENTATION. 179 



boiled down to crystallization. The sugar adhering to the 

 cotton is washed out and added to the blow-up ; the impurities 

 remain in the cotton. 



A late improvement in refining sugar is the employment 

 of centrifugal force for driving out the syrup from the crys- 

 talline grains of sugar. For this purpose, the syrup, with the 

 grains formed in it, is led into a drum fixed on a vertical shaft, 

 with its circumference formed by wire-gauze. The drum being 

 made to revolve with rapidity, 2000 times per minute, the 

 liquid mass is driven by centrifugal force to the circumference, 

 where the grains are detained by the gauze and the liquid 

 oozes through on the outside. It is a constantly acting force, 

 and it would seem as if the same efi'ect might be produced by 

 a broad and shallow filter, the lower part of which should be 

 partially exhausted by an engine. 



2. Fermentation. 



Practically, we have only to consider the manufacture of 

 alcohol and vinegar, but the consideration of fermented liquors 

 generally may be introduced. Vinegar is now chiefly made 

 from alcoholic liquids by simple oxidation, and the process is 

 a beautiful gift from chemical science to the arts. As there 

 is nothing new in relation to the vinegar process, we offer a 

 few observations in regard to the nature of fermentation, to 

 alcohol and wines. We notice a large work on Fermentation, 

 issued in Germany, entitled " Gahrungschemie in 3 Biinden, 

 1845, und 4ter (Supplement) Band, 1847," by Prof. C. Balling. 



Fermentation. — According to Helmholz's experiments, sub- 

 stances capable of undergoing fermentive changes in common 

 air, do not suffer them if the air have been previously ignited ; 

 from which he drew and confirmed a formerly advanced opinion 

 that fermentations arise from the exhalations of matter in the 

 act of fermentation, whose germs or seed are conveyed to 

 fresh matter capable of these changes, and impart to it their 

 own character ; and that these germs being destroyed by heat, 

 such air will not produce fermentation. 



