THE HIGH TEMPERATURE ORGANISM OF FERMENTING TAN-BAEK. 



Part i. 



By R. Greig-Smith, D.Sc, Macleay Bacteriologist to the Society. 



(Four Text-figures.) 



In the nianufaeture ot white lead, plates of luetallie lead are generally cor- 

 roded by the old Dutch fermentation process. As conducted at the works of 

 Lewis Berger and Co. at Rhodes, near Sydney, the fermentation stacks are l)uilt 

 up of layers of tap-bark with the lead contained in pots between successive layers 

 of bark. A layer of bark some twenty-four inches deep is first laid on the floor, 

 and on this are placed the earthenware pots each containing about three inches 

 cf dilute acetic acid and about eighteen perforated sheets of lead (buckles) all 

 resting upon a ledge in the jar. The jars are covered with timber and on the 

 timber a layer of sixteen inches of tampered tan-bark is placed; then comes a 

 layer of jnrs. then timber, and so the stack is Ijuilt up. Each tier of jars is 

 connected with the air at the top of the stack by means of wooden chimneys, the 

 vent of each chimney being covered with a piece of wood. When the fermenta- 

 tion is at its height, steam rustics out of the vents and tlie extraordinary thing 

 is that the temperature of the issuing steam is in the neighbourhood of 180° F. 

 This is a remarkably high temperature for there is some evidence in favour of 

 the fermentation being due to the activity of micro-organisms. 



The fermentation occupies about four montlis and, in its course, the lead is 

 carbonated with an efficiency of from (iO to 80 Sc- w-hile tiie temperature, starting 

 at about 140° F., rises during the second month to from 180° to 190° and tlien 

 falls to about 140° when the stacks are drawn. The bark darkens in colour, 

 shrinks in volume and becomes less fibrous. It is used again, but in order to 

 adjust the wastage and to improve the texture, it is mixed with one part of new 

 bark for every four parts of old teiuiierod bark when the stacks are made. 



The tanners of Sydney use wattle-bark in preparing their tan liquoi-s and 

 Lewis Berger and Co. have found that the fermentation of this kind of bark 

 requires a different treatment from the barks used in other parts of the world. 

 A preliminai-y fermentation or tempering is necessary. This consists in storing 

 the bark in a central reserve or alley and watering it daily foi' about a fortnight. 

 The temperature of the mass rises to well over l)lood heat, but not to the tem- 

 perature tliat it attains in the stacks. One can see lumps of bark on the to]! of 



