INTRODUCTION. 



to use the circalar filter papers, which are prepared 

 with hydrochloric and fluoric acid. In addition, some 

 soft absorbent blotting paper is constantly required 

 for taking up excess of moisture" from slides, cover- 

 glasses, etc. 



31. Litmus paper, blue and red. This is absorbent 

 paper, coloured with litmus solution ; a drop of the 

 solution to be tested is allowed to fall upon it from a 

 glass rod. The more sensitive the litmus paper is, 

 the more useful is it, but of course the more diflScult 

 is it also to work with. The blue and red papers 

 should be kept separate, and should be protected from 

 the light, preferably in large bottles with smooth 

 stoppers, which have been smeared over with vaseline, 

 the bottles themselves having been blackened with 

 varnish. 



32. Cotton wool. Clean cotton wool free from 

 grease, such as can be bought from pharmaceutical 

 chemists. 



38. India-rubber stoppers and caps for test-tubes 

 and india-rubber tubing. Some of the stoppers 

 should be perforated. 



34. Platinum wire of about '8-1 mm. in thickness. 

 For most purposes only short lengths of the wire 

 are needed ; but as long pieces are required, as for 

 anaerobic cultivations, it is as well to have it in 

 pieces about 12 cm. long. A few mm. of the wire 

 are fused on to the ends of thick glass rods ; some 



