IN EXTRA-TROPICAL COUNTRIES. 3 



Acacia decurrens, Willdenow, var. mollissima.* (A. mollissima, 



Willd.) 



The Black Wattle. From the eastern part of South Australia, 

 through Victoria and New South Wales, to the southern part of 

 Queensland ; a small or middle-sized tree. Its wood is used for 

 staves, for turners' work, occasionally also for axe- and pick- 

 handles, and many other purposes, and it supplies an excellent fire- 

 wood ; a chief use of the tree would be also to afford the first 

 shelter, in treeless localities, for raising forests. Its bark, rich in 

 tannin, and its gum, not dissimilar to gum-arabic, render this tree 

 highly important. The English price of the bark ranges generally 

 from 8 to 11. In Melbourne it averages about 5 per ton. It 

 varies, so far as experiments made in my laboratory have shown, in 

 its contents of tannin from 30 to 54 per cent, in bark artificially 

 dried. In the mercantile bark the percentage is somewhat less, 

 according to the state of its dryness it retaining about 10 per 

 cent, moisture. 1 \ Ib. of Black Wattle-bark gives 1 Ib. of leather, 

 whereas 5 Ibs. of English Oak-bark are requisite for the same 

 results, but the tannic principle of both is not absolutely identical. 

 Melbourne tanners consider a ton of Black Wattle-bark sufficient 

 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 care- 

 fully 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 gray 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 mimosa-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 

 fluid extract of Wattle-bark was shipped to London, fetching then 

 the extraordinary price of 50 per ton, one ton of bark yielding 

 4 cwt. of extract of tar consistence (Simmons), thus saving much 

 freight and cartage. For cutch or terra japonica the infusion is 

 carefully evaporated by gentle heat. The estimation of tannic acid 

 in Acacia 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 and determining the weight of 

 the tannic principle obtained by evaporating the filtered alcoholic 

 solution to perfect dryness 



