SEPARATION OF ANAL ROBES. 



69 



sulphuric acid and pure zinc. It is passed through three 

 wash-bottles as in Fig. 21. In the first is placed a solu- 

 tion of lead acetate (i in 10 of water) to remove any traces 

 of sulphuretted hydrogen. In the second is placed a i in 

 10 solution of silver nitrate to remove any arsenietted 

 hydrogen which may be present if the zinc is not quite 

 pure. In the third is a TO per cent solution of pyrogallic 

 acid in caustic potash solution (i : 10) to remove any traces 

 of oxygen. The tube leading from the last bottle to the 



FIG. 21. Apparatus for supplying hydrogen for anaerobic cultures. 



a. Kipp's apparatus for manufacture of hydrogen, b. Wash-bottle 

 containing i-io solution of lead acetate, c. Wash-bottle containing i-io 

 solution of silver nitrate, d. Wash-bottle containing i-io solution of 

 pyrogallic acid. (/', c, and d are intentionally drawn to a larger scale 

 than a to show details.) 



vessel containing the medium ought to be sterilised by 

 passing through a Bunsen flame, and should have a small 

 plug of cotton wool in it to filter the hydrogen germ-free. 



Separation of Anaerobic Organisms. (a) In glucose 

 gelatine. A ij inch test-tube has as much gelatine put 

 into it as would be used in the Esmarch roll-tube method. 

 It is corked with an india-rubber stopper having two tubes 

 passing through it, as in Fig. 22. The ends of the tubes 

 are partly drawn out as shown, and covered with plugs 

 of cotton wool. Three such test-tubes are prepared, and 



