The inquiries into the value of a series of indigenous substances likely recommendable for tanners' use, instituted in our phytochemical laboratory, have not as yet progressed far, the processes of investigation involving considerable sacrifices of time. It is intended to contrast the percentage of tannic acid contained in barks already in use here with that of many others probably much richer. Besides, it will be of importance to ascertain the extent of tannizing principles of the gum-resins exuded by the various eucalypts, and to tabulate also the relative quantity of tannic acid in many kinds of foliage. In an annexed table the first results are given of the analyses instituted with great care and patience by Mr. C. Hoffmann. Of many eucalypts the resinous exudations may be obtained in rather large quantity and with great convenience. The supply available at the places where the artisans of sawmills or splitters operate is actually boundless. Often the resin is most easily obtained while still in a state of solution, from which it is readily reduced to dryness or concentration. In either form the gum-resin might constitute an extensive article even of export. The following kinds are exhibited:—
|1.||Gum-resin of Eucalyptus corymbosa (Sm.), the Blood wood tree of Gippsland and New South Wales.
|2.||Of Eucalyptus amygdalina (Labill.), the Messmate tree of some districts of Victoria; also found in Tasmania.page 40
|3.||Of Eucalyptus leucoxylon (F. M.), a tree not uncommon in South Australia, Victoria, and New South Wales.
|4.||Of Eucalyptus rostrata, the Red Gumtree, so universal in Australia. This special kind is preferred to others as a therapeutic, a stringent, and is particularly administered in Europe and India in cases of diarrhoea which assumed a chronic state. To this category of objects belongs also a sample of Venetian sumach, or scotino, obtained from Rhus cotinus, cultivated in the Melbourne Botanic Gardens. There is nothing to prevent this plant being reared here quite as well as on the Mediterranean shores as a dye and tanning article. Tanners' bark, after having served its purpose, might perhaps in some instances be utilised as paper material, and as a source of acetic acid. In reference to this subject, Mr. Hoffmann instances the patent of Mr. A. P. Halliday, of Salford. The coal even is utilised again for steel manufacture, for manure, and for deodorising purposes. Merely to show that the tanning substances could also be employed for writing ink, the bark of Acacia penninervis was chosen as a source of tannic acid for the ink exhibited. For black and some other dyes, several of the barks alluded to are available.