132 SOIL BACTERIOLOGY 



(e) Of this solution take 50 c.c, and add to it, drop by 



drop, ethylamin (33 per cent, solution) until the 

 yellowish-brown precipitate which forms at first 

 is entirely dissolved and the fluid is clear. Only 

 a few drops are required. 



(f) Float the cover-slips in a little mordant contained 



in a Petri dish which is heated over a water-bath 

 for five minutes. 



(g) Take the dish off the water-bath, and as soon as the 



preparation becomes slightly opalescent, wash 



thoroughly in distilled water. 

 (h) Then heat a few drops of the ethylamin-silver 



sulphate solution upon the mordanted cover 



preparation until it just steams and the margin 



appears black. 

 (i) Wash and mount in balsam. 



