WATTLES AND WATTLE-BARKS. 27 



place to place. It does not pay to cart the trash far, but a few square miles 

 of wattle country will keep a factory going. The utilisation of thinnings 

 allows the cultivation of the tree thickly on waste ground, and to begin cut- 

 ting the third year. European tanners are quite accustomed to the use of 

 such extracts, but it is said that it will be very hard to introduce it into the 

 colonial tanneries." (Chemist and Druggist, 1886.) 



These works are still in successful operation, although mucilage still 

 gives some trouble. Wattle twigs are rich in gum and mucilage, and 

 some cheap process, which will get rid of these substances and leave the 

 tannic acid uninjured, is a desideratum. 



I have received many inquiries as to whether the difficulty has been over- 

 come, but I have had to reply in the negative, as far as a commercial process 

 is concerned. There is very little gum in clean-grown bark, but far more in 

 chopped twigs ; extract will not be made from the former except in almost 

 inaccessible districts. 



Of course, the extract in all stages of its manufacture must be preserved 

 from contact with iron. Wooden vats are employed, and the heat for evapo- 

 ration is obtained from hot water or steam. The waste bark, chips, &c., 

 used in the preparation of the extract are first digested in cold water, and 

 by having a series of vats, with communicating tubes or siphons, a charge of 

 bark can be transferred from one to another until it is exhausted to such an 

 extent that the small remaining percentage of tannic acid can only be 

 removed by hot water. 



The vats are constructed so as to expose a maximum of evaporating surface 

 to the atmosphere, and if the evaporation can be carried on wholly or in part 

 by means of the heat of the sun, so much the better, firstly, because the 

 consumption of fuel will be minimised, and secondly, because the process 

 should be conducted at as low a temperature as convenient. 



The preparation of wattle bark extract has been attempted in all of the 

 colonies, but in only one has it passed the experimental stage, so far as I know. 

 The process is analogous to " concentration " in metallurgical operations, 

 for the tannic acid in bulky, unsaleable material can be highly concentrated, 

 and barks weak in tannic acid can be utilized for the same reason. The 

 industry of extract-making is tempting, and I am confident that there is 

 much money in it for some of our country districts whose circumstances are 

 favourable. I trust, therefore, that it will soon be the means of affording 

 profitable occupation to many people. 



The dark colour of extracts is an objection, and many experiments have 

 been undertaken with the view to minimise the evil, with no very satisfactory 



