66 CYANAMID — manufacture:, CHEMISTRY AND USES 



in the long run better than before. Practically, from the stand- 

 point of plant physiology, it seems necessary to define a poison 

 as a substance which, administered in quantities ordinarily con- 

 sidered small, produces functional disturbances ending ulti- 

 mately in permanent injury or death.^ 



In this connection it may be well to quote entire the con- 

 clusions of Dr. Paul Wagner after seven years of experi- 

 menting with lime-nitrogen, both in pot cultures and in the 

 field.2 



CONCLUSIONS OF DR. PAUL WAGNER. 



"i. The statement 'lime nitrogen is a plant poison and must 

 be converted by soil bacteria into ammonia and nitric acid in 

 order to act as a fertilizer' has led to many faulty conceptions 

 and is practically not correct. Poison, as is known, is a very 

 relative term, for poisons in great dilution are unharmful, and 

 non-poisons in great concentration are harmful. For instance, 

 perchlorate occurring in nitrate of soda is a decided poison. 

 If one sows 3 kg of perchlorate on a hectare of rye, 

 there will be a poisonous action. Chile saltpeter should 

 therefore contain not more than one-tenth of a per 

 cent, of perchlorate; it should be rejected if it con- 

 tains more than i per cent, of this poison. Likewise, 

 ammonium sulphocyanate is a real plant poison. In the year 

 1873, in No. 38 of the Hessian Agricultural Journal, I com- 

 municated a marked example of sulphocyanate poisoning. On 

 the Rudigheimer estate at Hanau a grain field of 4 hectares 

 was poisoned by an application of 100 kilograms of ammonium 

 superphosphate with 10 per cent, nitrogen, which later in- 

 vestigation showed to contain sulphocyanate. Therefore, this 

 extremely slight amount of sulphocyanate was sufficient to 

 cause a characteristic poisoning and to decrease the yield to 

 about one-third. It has also been learned that ammonium 

 sulphocyanate applied a greater or less time before sowing of 



» See also Pfeffer's Physiology of Plants, Ewart, Vol. II, 258. 



' Arbeit. Deut. Landw. Ges., Heft 129, 1907, p. 267. 



