76 Microbes and You 



Chamberland Candles. These are composed of mixtures of 

 silicon and kaolin, and are unglazed porcelain filters shaped like 

 a hollow candle open at one end. The candles can be sterilized in 

 the autoclave, attached to suction flasks, and the liquid to be freed 

 of organisms can be introduced into the open end of the candle 



Fig. 17. Some of the common filters used by bacteriologists. (A) 

 Seitz filter designed to operate with external pressure; (B) Small Seitz 

 filter, suction model; (C) and (D) Berkefeld filter candles mounted in 

 glass mantles. (From Textbook of Bacteriology, E. O. Jordan, and 

 W. Burroivs, 14th ed. Copyright 1945, W. B. Saunders Company, 

 Philadelphia.) 



and allowed to pass through the filter with the aid of negative 

 pressure applied to the side arm of the receiving flask. Bacteria 

 normally carry a negative charge. Chamberland candles possess 

 a positive charge. Great care must be exercised to insure that the 

 candles are not cracked. A minute crevice in the filter can allow 

 organisms to squeeze into the filtrate. 



