242 



METHODS OF CULTIVATION 



FIG. 132. Kipp's hydrogen apparatus, (a) connected up to two washing 

 bottles containing (b) lead acetate 10 per cent, solution, to remove H 2 S 

 and (c) silver nitrate solution to remove AsH 3 . A third washing bottle 

 containing pyrogallic acid 10 per cent, solution, rendered alkaline, to 

 remove any trace of oxygen, is sometimes introduced. 



FIG. 133. Improved gas apparatus; the metal is contained in a perforated 

 glass tube which is submerged in acid when the triangular bottle is upright 

 (a), but is above the level of the liquid when the bottle is turned on its 

 side (6). 



