IN EXTRA-TEOFICAL COUNTRIES. 3 



it averages about £5 per ton. It varies^ so far as experiments 

 made in my laboratory have sbown, 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. 

 li lbs. of Black Wattle bark gives 1 lb. of leatherj whereas 

 5 lbs. of English Oak bai'k 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 suflBi- 

 cient to tan 25 to 30 hides ; it is best adapted for sole leather 

 and other so-called heavy goods. The leather is fully as dura- 

 ble 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 oxyde salts of iron, and a violet colour 

 with sub-oxydes ; 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 quan- 

 tity 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-oxyde of iron, black pigments; and with the salts 

 of the full oxyde 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 iafusion 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 resi- 

 due in alcohol and determining the weight of the tannic prin- 

 ciple obtained by evaporating the filtered alcoholic solution to 

 perfect dryness. 

 The cultivation of the Black Wattle is extremely easy, being 

 effected by sowing either broadcast or in rows. Seeds can be 

 obtained in Melbourne at about 5 shillings per lb., which con- 

 tains from 30,000 to 50,000 grains; they are known to retain 

 their vitality for several years. Seeds should be soaked in 

 warm water before sowing. Any bare, barren, unutilised place 

 might most remuneratively be sown with this Wattle Acacia ; 

 the return would be in from 5 to 10 ye^rs. Full-grown trees. 



