670 TECHNIQUE 



Dilute Canada balsam with xylol until it acquires a very thin 

 watery consistence. Add sodium bicarbonate in excess. Shake 

 thoroughly, and allow to stand in a stoppered bottle for twelve 

 hours or more. Filter ; this is readily, though slowly, accomplished 

 if the dilution is sufficient. Permit the solution to stand in an 

 open vessel, protected from dust, until it evaporates to the proper 

 consistence for use. 



