4 GLASS APPARATUS IN COMMON USE 



calibre, and a batch of 1 8 by 1.5 cm. tubes usually con- 

 tains such extreme sizes as 18 by 2 cm. and 18 by 1.3 

 cm. Consequently, if a set of standard tubes is kept 

 for comparison or callipers are used each new supply of 

 so-called 18 by 1.5 cm. tubes may be easily sorted out 

 into these three sizes, and so simplify ordering. 



5. 5X0.7 cm., for use in the inverted position inside 

 the tubes containing carbohydrate media, as gas- 

 collecting tubes. 



These tubes, "unrimmed," may be of common thin 

 glass as less than two per cent, are fit for use a second 

 time. 



FIG. i. Bohemian flask. FIG. 2. Pear-shaped FIG. 3. Erlenmeyer flask 



flask. (narrow neck). 



, Bohemian Flasks (Fig. i). These are the ordinary 

 flasks of the chemical laboratory. A good variety, 

 ranging in capacity from 250 to 3000 c.c., should be 

 kept on hand. A modified form, known as the " pear- 

 shaped" (Fig. 2), is preferable for the smaller sizes 

 i. e., 250 and 500 c.c. 



Erlenmeyer's Flasks (Fig. 3) .Erlenmeyer 's flasks 

 of 75, ioo, and 250 c.c. capacity are extremely useful. 

 For use as culture flasks care should be taken to select 

 only such as have a narrow neck of about 2 cm. in 

 length. 



Kolle's Culture Flasks (Fig. 4). These thin, flat 

 flasks (to contain agar or gelatine, which is allowed to 

 solidify in a layer on one side) are extremely useful 



