FILTRATION OF SMALL QUANTITIES OF FLUID 25 



C. Duclaux's filter. The filter can also be fitted to a flask with three tubulures 

 (fig. 27). In this case the open end of the filter is wrapped round with cotton- wool, 

 which serves to hold the bougie in position in the neck of the upper tubulure E. 

 The tubulure D is sealed, and B is plugged with wool. After autoclaving, the wool 

 packing around the neck of the filter F is made air-tight by running a little melted 



FIG. 27. Laboratory bougie Duclaux's 

 arrangement. 



FIG. 28. Laboratory bougie Kitasato's 

 arrangement. 



wax ([paraffin or] Golaz's) over it. The tubulure B is connected to a water pump, 

 and the liquid to be filtered poured into E. On turning on the water the liquid 

 is drawn through the filter and collects in the flask. To distribute the filtrate, 

 break off the sealed end D and blow air into the flask through the wool-plugged 

 orifice B. 



D. Kitasato's filter (fig. 28) consists of a conical flask of thick 

 glass furnished with a lateral tube b, which when in use is plugged 

 with wool and connected to a water pump. 



The wide neck of the flask is fitted with a perforated india- 

 rubber bung through which the filter F is passed. The mouth 

 of the filter is attached by means of another india-rubber bung to 

 a glass bulb A. The technique is very simple : pour the liquid 

 into A, turn on the water pump, and the filtrate collects in the 

 flask B. The apparatus must of course be autoclaved before use. 



E. Martin's filter (fig. 29), as arranged for dealing with small 

 quantities of fluid, consists of a tube R, which can be connected 

 to a water pump through the tubulure A. Within it is a 

 moderately large test-tube T resting upon a pad of cotton- wool. 

 A small filter F is passed into the test-tube, and firmly fixed in 

 the mouth with the open end upwards. The tube R is closed 

 above with an india-rubber bung, through which passes a glass 

 funnel E the lower end of which is connected with the upper 

 (open) end of the filter. The liquid to be filtered is poured 

 into E, and being drawn through the filter collects in the tube T. 



FIG. 29. 



To sum up, there are three important considerations to be arrangement. 1 ' 

 kept in mind when using a filter for purposes of sterilization. 



(I) In every case the filter must be tested to make sure it is sound and free 

 from fissures ; (2) filters must always be sterilized immediately before use ; 

 and (3) subsequent contamination of the filtrate must be carefully guarded 

 against. 



