"212 Asö, Which Compound in certain plant-juices can liberate iodine etc. 



nie that among otlier substances soluble albumin as well as 

 pepton 1 ) can prevent tlie appearance of the iodine reaction 

 which very easily can be unterstood, since these Compounds can 

 bind some iodine thus rendering the formation of iodine- starcli 

 impossible. Hence it might be supposed that the alcoholic 

 precipitate just mentioned failed to give the iodine reaction on 

 account of having contained some soluble albumin. Since the 

 juice of the bulb contained some soluble albumin, it was further 

 not surprising to find that the juice of the bulb was capable 

 to prevent the iodine reaction in the juice of the bud, and 

 further that the boiled juice of the bulb did not prevent it 

 anymore. It was further tested whether the juice of the bulb 

 itself would yield the iodine reaction after removing the soluble 

 albumin. But after a few seconds boiling whereby the albumin 

 separated in flocculi, no iodine reaction was obtained in the 

 filtrate, although short boiling in neutral Solution does not 

 destroy the active Compound as I have mentioned above. 



The resistance of the active principle towards boiling heat 

 suggested a careful test for nitrites and indeed to my great 

 surprise the reaction of Griess for nitrites yieldet at once a 

 very decisive result. Hence the Liberation of iodine is due 

 not to any enzym nor to any peroxid, but to nitrite. 



It seems stränge that the occurrence of nitrite in plants 

 thus f ar was overlooked. It is true that Schönb ein more than 

 thirty years ago had supposed the existance of nitrite in plant 

 juices and further that Berthelot had assumed the formation 

 of nitrate in leaves and shoots from ammonia. But some authors 

 did not agree with these observations. The occurrence of nitrite 

 in plants is indeed surprising, since we know that nitrites are 

 very poisonous for plants, containing an acid plant juice 2 ). But 

 in this regard we must not overlook that the reaction of Griess 

 .shows nitrite even in exceedingly high dilution, and that nitrous 

 acid is not present here in the free state since the acidity of 

 Sagittaria buds is hardly perceptible 3 ). I assume that the nitrous 



x ) It was Mr. Shibata wlio called first my attention to this fact, 

 befose I commenced this investigation. 



2 ) O. Loew, Natürliches System der Giftwirkungen, p. 61 and p. 107. 



3 ) Not only the buds, but also the shoots 8—10 cm long of Sagittaria 

 yielded the iodine reaction as well as the Griess reaction. But, when the 

 young plants reached the height of 18 cm, tho reaction of Griess was no 

 more obtained, although still the iodine reaction can be observed. However, 

 the reaction of diphenylamine can be obtained when carried out with 

 proper care. 



In making the tests for nitrous acid, very much care must be taken, 

 since in laboratories where many gas names are burning, traces of nitrous 

 acid are present in the atmosphere and even adhering to various objects. 

 (See O. Loew: Ber. D. ehem. Ges. Vol. XXIII. p. 1444). Hence, in my case, 

 all vessels were first washed with distilled water and further the moistened 

 saw dust in which the shoots were grown, was tested for nitrous acid. 

 Further control tests were regularly made. The produetion of nitrous acid 

 by rianies, may have caused also an error in the Observation of Bonnema, 

 mentioned in the Chemiker-Zeitung. 1903. No. 14. 



