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. 



(/") 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. 



(ti) 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. 



