( 688 ) 



I obtained the best results with a paper pulp prepared bv trituratiiip: 

 Swedish filterpaper in water, care being taken that this pulp contained 

 27„ of cellulose. 



In order to obtain a tiiorou,i>ii denitrification Avith cellulose, a 

 bottle holding about 200 cc. is tilled with the following mixture: 



Tapwater^) 100, paper 2, KNO., 0,25, K.HPO, 0,05, 



and the mixture is then inoculated witii a few cc. of mud (from a ditch). 



The bottle is then quite filled up in the manner described in 

 niv former coiiuiMiiiicalinn (I.e.), to prevent access of aii-, and the 

 cultivation takes place at 35°. 



After the lapse of about 8 days the action is perceptible, luit oidy 

 after 12 days a brisk fermentation sets in. The cellulose is carried 

 to the top by the generated gasbubi)les and a (iiianlily of liquid is 

 forced out of the bottle by the slimy froth, while the pa[)er-pulp is kept 

 back by the stopper. In the beginning of the process a strong formation 

 of nitrite may be observed, but the nitrates and nitrites soon decrease 

 and after the lapse of about 15 days, these compounds have disappeared. 

 The liquid is now carefully decanted from the pulp, which may be 

 done without appreciable loss of ]iaper tibres, as these readily agglo- 

 merate. The bottle is then refilled with the following liquid: 



Tapwater 100, KNO, 0,25, K.HPO, 0,05. 



The process now stai-ts much (pucker than in the first cultivation, 

 the nitrate disappears in 4 or 5 days and by repeating the operation 

 a few times more, cultures may be obtained of an increasingly active 

 denitrifying power, with which it is possible to completely reduce in 

 one or two days 0.5 gram of KNO, dissolved in 200 cc. of water. 

 This method of working is |)referable to adding a fresh quantity of 

 KNO3 to the original culture, as it is then not possible to reduce 

 on the whole more than about ^/^ "/„ of KNO, (calculated in regard 

 to the quantity of the liquid used, or 25 "/„ in regard to the cellulose) 

 because the process then comes to a standstill by the alkaline potas- 

 sium carbonate formed from the iiitrate. 



If now a sterilised liquid is inoculated with the strongly denitrifying 

 rough culture and the cultivation allowed to take place under the same 

 circumstances as described above, the action commences much more 

 rapidly than m the first preliminary experiment, whilst the same 

 phenomena occur. Even after repeating the inoculation ten times, 

 no change in the intensity of the process could be observed. 



Not only paper, but raw tlax fibres, cottonwool and linen appeared 



1) From the Downs at Loosduinen. 



