TANNINS FROM WATTLE BARK. 
of the gums is objectionable. Before the war large quantities of 
Australian barks, including those of wattle, mallet, and mangrove, 
were utilized in Germany for the production of extracts, and these 
German extracts were imported into Australia. Chemical research 
in Germany had solved the problems of decolourization and of the 
removal of undesirable gummy matter, and these problems should be 
investigated in Australia. : 
In the early stages of their work, the Executive Committee of the Institute 
obtained a report from the New South Wales State Committee on the: tanning 
industry in that State. In that report attention was directed to the fact that 
at many of the New South Wales tanneries no attempt was made to determine 
the amount of tannin, or even of extract, in the tan liquors prepared, and 
no analyses were made either of the original bark or of the spent bark. ‘The 
proportion of bark and water used was not weighed or measured, and the water 
was in some cases used cold, in others hot, whilst in the latter the exact 
temperature was not determined. The tanners rely on the appearance and taste 
of the liquid, with the result that a great deal of time and material is often 
wasted before the required liquor is obtained. 
It is true that in some few tanneries in Australia chemists are employed to 
analyze the barks, and, to some extent, to control the tanning process, but in 
the great majority conditions are as above described. The tanners interviewed 
admitted that their methods left much to be desired, and that they would 
welcome any scientifically worked-out method of procedure which would enable 
them to obtain extracts of definite and uniform strength. The Institute there-’ 
fore appointed a Special Committee to investigate processes ,of extraction of 
tannin from wattle bark, with a view to the determination of a standard and 
Scientific method of procedure under practical conditions. The members of the 
Committee were Professor Fawsitt (chairman) and Messrs. B. Bailey, F. A. 
Coombs, F. B. Guthrie, and H. G. Smith. The experimental work was carried 
out at the Tanning Department of the Sydney Technical School by Mr. F. A. 
Coombs. A summary of the report of the Committee is given in the following 
pages. 
Meruops Apoprep IN THE INVESTIGATION. 
(a) Introductory.—The primary object of this investigation was to obtain 
a more efficient method at Australian tanneries for extracting tannin from 
wattle bark. Two factors to be noted in connexion with this work are (1) that 
the Australian tanners-require strong or highly concentrated liquors, and 
(2) that the tanners are at present using extraction plants constructed in 
accordance with their own ideas. Research then had to be conducted on lines 
that would not give weak liquors, the experimental plant being, if possible, con- 
structed in such a way that it could be duplicated in the various tanneries 
without any costly alterations. Extraction processes, which included sprinklers 
or autoclaves, were not considered suitable for the extraction of tannin from 
wattle bark under the conditions described above. ; 
South African patents cover a process which may give good results for the. 
manufacture of extracts under local conditions; but for Australian requirements 
(especially in reference to extraction at the tanneries) it is necessary that the 
bark should be dry. The agitation of the bark during the extraction process 
may have certain advantages over a process which does not include this mechanical 
_ treatment, but only results covering a reasonable working period will give the 
value of this process, and, from the small amount of information available, it 
does not appear to have been found of any special value to Australian tanners. 
The best plant for extracting tannin from bark at the tanneries is probably 
the “press leach battery.” This may be described as the battery required 
for an open diffusion and continuous process. When the liquors are forced around 
the battery by gravitution we have what is generally called the “press leach 
system.” Proctor and others have described this plant, and the former gives 
useful information which is directly related to the extraction process. 
(b) Haperimental Processes as carried out by the Committee.—Before the bark 
was placed in the extraction vats it was passed through a mill and reduced to 
the state known in the trade as “ground” bark.’ By grinding in a mill the 
tanner reduces the size of the particles of bark: - Generally, .the particles of 
I51 
