Asö, Which Compound in certain plant-juices can liberate iodine etc. 2 11 



sonie objects certain ferric Compounds 1 ) or traces of nitrites. 

 The following linis will doubtless prove of some interest in 

 regard to this qnestion. 



Experiments w i t li b u d s. 



While shoots of barley, bamboo, pea and Colocasia did not 

 give tlie iodine reaction, but very well tlie guaiac reactions, 

 sections of potato shoots 2 ) yielded directly the iodine reaction 3 ). 

 The cold prepared extract behaved alike. In a second case, 

 with shoots of potatoes from another source, however, the iodine 

 reaction failed, altough oxidase, peroxidase and jtf-guaiacolase 4 ) 

 were present. 



Of considerable interest were the observations made with 

 the tubers and buds of Sagittaria sagittifolia. The cold prepared 

 aquoeus extract of the bulb gave no iodine reaction, but it gave 

 the blue guaiac reaction, while the extract of the buds yielded 

 directly both reactions. Eight buds of Sagittaria were extracted 

 with 100 c. c. water; a portion was tested directly and another 

 after boiling for 30 seconds. In the former case, oxidase, per- 

 oxidase and jtf-guaiacolase were easily recognized by their 

 reactions, while in the latter case, no trace of this reaction was 

 more obtained. But very different were the phenomena in 

 regard to the iodine reaction. Not only tho unboiled, but 

 also the boiled juice yielded this reaction with great 

 intensity after addition of some acetic acid 5 ). Even 

 boiling for 2 minutes did not alter this result ). It is therefore 

 undeniable, that hereby another proof is furnished that the 

 substance wich gives the guaiac reaction for oxidase is not 

 identic with the substance that give the iodine reaction. It was 

 of interest to me to decide whether in the bulbs a Compound 

 would be present that can prevent the iodine reaction which so 

 easily and intensely is obtained in the buds. Hence four bulbs 

 were crushed after removing the skins and macerated with 

 100 c. c. water. The filtrate was mixed with alcohol, whereby 

 a considerable precipitate was obtained. This was collected on 

 a filter, washed and after well pressing between filter paper, and 

 evaporation of the alcohol at common temperature, extracted 

 with water and tested again. The iodine reaction failed however 

 while the guaiac reaction was obtained. Further tests convinced 



!) It may in this connection be of sonie interest to mention tliat 

 ferric sulfate even in a dilution of 1 : 10000 can liberate iodine. 



2 ) The tubers did not give this reaction, as was mentioned before. 



3 ) A few di'ops of a 10°/ acetic acid always here to be added to 

 obtain this reaction. 



4 ) See above, p. 3, footnote on guajacolase. 



5 ) A bhnd control test with acetic acid and potassium iodid-starch- 

 paste showed no reaction whatever. 



6 ) Bach and Chodat mention that after heating to 80° C. the iodine 

 reaction is no longer obtained. This is, however, probably only the case 

 when the acidity of the juice is more marked than in the case of the 

 Sagittaria buds. 



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