INTRODUCTION 



31 



preparation may be complete, the method of denitrification, as it has 

 been termed by Jacques Duclaux, should be included. 



Membranes prepared from collodion are simply a gel of nitrocellu- 

 lose. Such membranes possess very low adsorptive capacities, but 

 this property can be diminished still further by decreasing the thick- 



d.. 



Fig. 4. Denitrified Ultrafilter Arranged for Drying 

 a, celloidin sac; b, ligature; c, supporting glass tube; d, column of water; e, 

 rubber stopper;/, pinch-cock, 



ness of the membrane, and this is what happens when the nitrocellulose 

 is transformed into pure cellulose by denitrification. At the same time 

 this procedure increases the toughness of the membrane. 



For denitrification, mount the sac upon its supporting tube, adjusting 

 it as has been described, but instead of immersing it in distilled water, 

 substitute a 25 per cent solution of ammonium hydrosulfide in dis- 



