BY R. GBEIG-SMITH. 

 Experiment with Cellulose and Bark-extract. 



97 



One cannot say very much about this experiment for with 0.25 gram of 

 asparagin and 4 grams of celhtlose there should have been muc-h more gas given 

 off, and it would tiierefore appear a« if the carbon dioxide had been derived 

 from the bark extract. On the sixth day, the liquid control did not appear to 

 have much bacterial growth although it contained active bacteria. The test 

 flask contained a sodden mass of cotton with very little loose water. Both had 

 the same slightly alkaline reaction to litmus and phenolplithalein papers. It is 

 possible that if no alkali had been added on the .second day tbe results might 

 have been different. 



Conclusions. 



There are many points connected with the fermentation of the barks yet 

 to be determined, but so far as the investigatiim has gone, certain facts have 

 been elucidated. The aetive agent is a spore-bearing rod with an optimum tem- 

 perature of 60° C. for laboratory work. It is capable of fenuenting the spent 

 wattle-bark of tanneries after the bark has been treated or "tempered." The 

 tempering is undoubtedly a mixed fermentation and in it a temperature of 

 from 40° to 50° is attained. Its object is to maintain a vigorous growth of the 

 active bacteria, but incidentally a certain destruction of the organic matter by 

 moulds, yeasts and bacteria probably occurs. Raw tan-bark which has been 

 heated to a sterilising temperature is not easily fermented by the bacteria and it 

 is probable that this is caused by the inhibiting action of the residual tannin 

 products, because treatment of the heated raw bark wifh alkali and air so alters 

 the bark that fermentation can ensue. Tests have yet to be made upon unheated 

 raw bark, but it is likely that it will behave similarly to the heated bark. Heated 

 tempered bark is easily fermented and is not influenc-ed by treatment with alkali 

 an<l air. 



It will be remembered that when tlie stack is liuilt, one part of new bark is 

 mixed with four parts of tempered bark and when the stack is drawn the new 

 bark is found to have been altered in character. It has become black and non- 

 fibrous, indicating that some change has occun-ed and, as the bark is now easily 

 fermentable, the assumption is that tlie long fermentation has, among other things, 

 destroyed the inhibiting bodies, be they tannins or others. 



