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^Acacia rhrurrens, WUld., Black Watth\ A small or middle sized 

 tree. The bark constitutes the tanner's „wattle bark". It is rich 

 in tannin, and this faot, together with the many uses of the gum deri- 

 ved from the tree, make this one of Australia's most valuable plants. 



„In England the price of wattle-bark runs from about £ 8 to 

 ë 11, in Melbourne about i' 5 a ton. It varies, so far as 

 experiments made in my laboratory have shown, in its contents 

 of tannin from 30 to 54% in bark artificially dried. In the 

 mercantile bark the percentage is sorae what less, according to 

 the state of its dryiiess, it retaining about 10 percent moisture; 

 I5 Ib. of black wattle-bark gives 1 Ib. of leather, whereas 5 Ibs. 

 of English oak-bark are requisite for the sarae results, but the tannic 

 principle of both is not absolutely identical. Melbourne tanners 

 consider a ton of black wattle-bark sufficiënt to tan 25 to 30 hides ; 

 it is best adapted for sole leather and other so-called heavy goods. 

 The leather is fully as durable as that tanned with oak-bark, and 

 nearly as good in colour. 



„Bark carefully stored for a season improves in tanning power 

 10 to 15 per cent. From experiments made under the author's 

 direction it appears that no appreciable difference exists in the 

 percentage of tannin in wattle-bark, whether obtained in the dry 

 or in the wet season. The tannin of this Acacia yields a grey 

 precipitate with the oxide-salts of iron, and a violet colour with 

 sub-oxides; it is completely thrown down from a strong aqueous 

 solution by means of concentrated sulphuric acid. The bark 

 improves by age and desiccation, and yields about 40 per cent of 

 catechu, rather more than half of which is tannic acid, Bichromate 

 of potash, added in a minute quantity to the boiling solution of 

 üf/mo.sa-tannin, produces a ruby-red liquid, fit for dye purposes; 

 and this solution gives, with the salts of sub-oxide of iron, black 

 pigments, and with the salts of the full oxide of iron, red-brown 

 dyes. As far back as 1823, a tluid extract of wattle-bark was 

 shipped te London, fetching then the extraordinary price of ^ 50.— 

 per ton, one ton of bark yielding 4 cwts of extract of tar-consistence 

 (Simmons), thus saving much freight and cartage. For Cutch or 

 Terra Javanica the infusion is carefully evaporated by gentle heat, 

 The estiraation of tannic acid in Jcacm-barks is effected most 

 expeditiously by filtering the aqueous decoction of the bark after 

 cooling, by evaporating and then re-dissolving the residue in alcohol 



