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reduce nitrates to nitrites; lie lias, therefore, proved denitrification, in 

 the largest sense of the word, as being possible with cellulose, but from 

 his short notes we do not understand his modus operandi or the nature 

 of the cellulose used in the experiments. Dkherain^) positively states in 

 '1897 that lie has not been able to observe denitrification with llax 

 fibres and the attention of Omklianski (I.e.) has also not l)een attracted 

 to this process when engaged in the study of the fermentations of 

 cellulose. This investigator induces the methane or hydrogen fermen- 

 tation by means of a nitrogenous food composed of ammonium sul- 

 phate or phosphate and sometimes he also adds asparagine, peptone, 

 extract of meat or of manure. Strange to say, he has not ^vorked 

 with nitrates ; had he done so, he would have noticed that the nature 

 of the process is completely modified, foi- instead of the methane or 

 hydrogen fermentation denitrification sets in ^vhicll is characterised 

 by the production of free nitrogen and carbon dioxide. 



In a previous research ^) on accumulation experiments with deni- 

 trifying bacteria, I have shown that these aerobic organisms can 

 oxidise many different organic substances out of contact Avitli air 

 with the aid of nitrates or nitrites, according to the formulae: 

 5 C + 4 K N(:)3 + 2 H,0 = 4 K H VO, + 2 N, + CO.^ 

 3 C + 4 K NO, + H,0 = 2 K H C()3 + K, VA), + 2 N,. 



Denitrification was noticed with lactates, tartrates, citrates, malates, 

 acetates, glucose, starch, asparagine, gelatin, broth, methyl and 

 ethyl alcohol and it Avas, therefore, tiiought worth while to try 

 whether cellulose might also be used as a source of carbon supply 

 in the deiiitrificationprocess, which indeed proved to be the case. 



Before describing my experiments in detail, I Avill first make some 

 ]-eniarks as to the nature of the cellulose employed. As a rule Swedish 

 tilterpaper \vas taken. Although this paper gives a faint blue colour 

 with a dilute solution of iodine it was found to be very difficult to 

 remove the impurity with boiling Avater; the so-called starch-free 

 paper from Scpileicher and Schüll, which has been purified Avith 

 hvdrotluoric acid, showed the same reaction. Sometimes linen tissues 

 and cottonwool were used, from which the first also gives a blue 

 coloration \\\{\i dilute solutions of iodine, whilst tlie latter does not 

 show this reaction. The little impurities, present in the cellulose 

 employed, were howe\er, of no moment in my experiments, as 

 the effect on the cell walls "was judged by the changes observed 

 by a microscopical investigation. 



1) Recherches sur la reduction des nitrates, Ann. agron. t. 23, 1897. 

 -) Van Iterson, Accumulation experiments with denitrifying bacteria. Proc. Acad, of 

 Science, Amsterdam July 190:i. 



