M 



HIGH TEMPERATURE ORGANISM OF FERMENTING TAX-BARK, 



suiked into tlio apparatus. Two flasks in series, each containing 50 e.e. of N 10 

 baryta watei', coloured with phenolplithalein, were found to sutiice for trapping 

 all the CO2. Tlie deeolurisation of the lirst flask was the signal for titrating the 

 liquids in both flasks. The flasks themselves were fltted with wide tubes to 

 avoid any tendency to blocking by the barium carbonate, which is largely de- 

 posited around the end of the inlet tube. It was unnecessary to have a flask 

 of water in the thermostat connected with the other containing the bark in 

 order to prevent the latter becoming too dry. 



In the experiment about to be described the air passed through a tube of 

 soda-lime, tlien through a AVoulft' bottle coutaiuing N, 3 baryta water, thence 

 through the flask with the bark, through two \Yanklyn flasks in series containing 

 baryta water and sometimes through an air-regidating flask to an air-resei-\-oir 

 connected with a suction pump. 



The stack -hark that was used was acid, and a rough test indicated that 

 the acidity was about 2.25 e.c. of N/1 acid per 100 grams of dry bark. The 

 acidity is of some importance, because we have seen that the thermophilic bac- 

 teria develop from the Ijark only when it is made alkaline. The gas in saccharose 

 media also formed in the presence of a certain amount of alkali. One might 

 think, therefore, that in the stack, the bark would make the attached water acid, 

 and thus prevent the growth of the bacteria and the fermentation of the bark. 

 But conditions that affect liacteria in the laboratory do not have the same influence 

 on the large or manufacturing scale. The acetic bacteria, for example, work at 

 a temperature of 45° in a 5,000 gallon vat and they would not gi'ow at this 

 temperature in the laboratory in small bottles. The thermophilic rod from the 

 stack-bark gi'ows at 80° in the corroding stacks, but it grow-s best at 60° in the 

 laboratory. It mus?t also be remembered that in the laboratory we desire to see 

 results in a few days while on the large scale, as in lead corrosion, the fermen- 

 tatiim goes on for several months. The slow fermentation will probably ensure 

 a l)etter corrosion and in any case a rapid evolution of gas. if it could occur, 

 might be of the nature of an explosion. So much for the condition of tempera- 

 ture. With regard to the acidity, one can imagine that bacteria will slowly 

 produce change in large masses of fermentable organic matter such as silage, or 

 acetic wort having an acidity that would render them inactive on a laboratory 

 scale. 



Some of the tempered bark was dried at 130° and divided into two jwrtions 

 of 30 grams each. These were Iioated in the oven at 150° for two hours. Each 

 was treated with 20 c.c. of N/10 sodium hydrate and 50 c.c. of water, but in 

 the case of the test flask the water contained a suspension of bacteria (race 73). 

 The flasks were connected up with the apparatus previously described. 



Evolution of Carbon Dioxide from Tempered Bark. 



