4H S. SAWA. POISONOUS ACTION OF UREA. 





On April 22. 

 cm. 



On May 30. 

 cm. 



Urea. 





85.0 



67.0 (decrease 18) 



B 



81.0 



52.0 ( „ 29) 



Control. 



A 



68.0 



127.0 (increase 59) 



B 



69.0 



127.0 ( „ 58) 



The injurious action of urea even in the high dilution of 

 0.5 per mille is therefore quite evident. This recalls another 

 observation of Loew and Bokorny on algae. 1 Spirogyra was 

 much injured within five days in a solution of 0.2 per cent, urea, 

 and microscopic observation showed that it was especially the 

 chlorophyll bodies that were attacked. 2 Probably in these 

 organoids, the urea is too readily split up into ammonia and 

 carbonic acid, and the nascent ammonia killed the chlorophyll 

 bodies. The fact that urea in such dilutions does not act poison- 

 ously on fungi and bacteria, and is even a good source of nitrogen 

 for them, would be in accord with this explanation. 



1 Journ. f. prakt. Chemie, Vol. 36 (1887) p. 379. 



2 Thio-urea acted still more poisonously. 



