The Pamphlet Collection of Sir Robert Stout: Volume 6
Products of dry Distillation of Victorian Woods
Products of dry Distillation of Victorian Woods.
In placing before the visitors of the Intercolonial Exhibition the products obtained by dry distillation from a series of the most widely-distributed timber trees of this country, I had a double object in view. I wished to render known new sources of employment for both labour and capital; and I desired likewise to point to inducements hitherto very imperfectly understood, for the occupation of a vast extent of the densely timbered ranges, in which, as yet, no dwelling is to be found. The climate of these free mountains is salubrious, and, indeed, delightful, and the material for lucrative work is accessible in unbounded abundance. While in northern countries the fir, which yields us the Stockholm tar, is so precious as to admit of the selection of roots and branches alone for the purpose of distillation, the stems being needed for the softwood deals which we import, we can here subject, without restrictions dictated by economy and by limited supply in old countries, an infinitely larger mass of wood to industrial processes. While in northern countries the inclemency of the climate renders forest operations for a part of the year surrounded with difficulties, and while the toiling labourer there can but raise a scanty supply of food from the earth, we can in this genial zone call forth in exuberance cereals and other main- page 23 stays of aliment from a grateful soil, and can turn into ever-verdant and never-frozen valleys the pasture animals needed for our local sustenance. Moreover, by the cultivation of many highly valuable plants, excluded from less genial zones, and of such plants as need more humidity and more shelter than our open cereal tracts do afford, the paths of prosperity become still more numerous, by which families may seek for their hardy offspring independence and healthy occupation. Thus, they may engage in work which yields for paper-mills the raw material, in the production of tar, acids, and potash, in the artless distillation of volatile oils; and these occupations may be combined in sheltered glens with the rearing of Chinese tea, Peruvian bark, senna, cork, sumach, perhaps even coffee, and very many other products highly remunerative, while less secluded portions of the ranges, under singular facilities for irrigation, will yield olives, vine, oranges, and an almost endless variety of other fruits.
Wherever, therefore, the miner has vainly searched for the metallic treasures of the soil, we should see, under circumstances so favourable to rural pursuits, the dwellings of families arise. In sketching a hopeful picture of future forest life, I have not thought of Victoria alone. The results of the investigations in some of the new timber resources, here preliminarily placed on record, might readily be a guidance to settlers in the woods in all the surrounding colonies, where most of the trees here experimentally operated on likewise occupy extensive localities not readily accessible to cereal culture or ordinary pastoral pursuits. The primary information furnished on this occasion refers to the yield of tar, wood vinegar, and wood spirits from such of our timber as in all instances as stated are of vast prevalence, and in most cases restricted to barren rises or to swampy depressions.
The percentage of tar, and the strength of the wood vinegar from native timber, as defined in the adjoining table, bears fair comparison with the results attained in other countries from other trees. But for greater facility of comparison, a scale from the yield of some European trees is in juxtaposition annexed. Though there is no great material difference between the tars and vinegars obtained by the heating of various woods under exclusion of air, I found it desirable to exhibit the full series of the products. The wood employed was air-dried, the amount torrefied in each case 25 lbs. The details of the operation were well carried out by Mr. Hoffmann, to whose skill I also entrusted the determination of the percentage of yield of the tar and vinegar, and again the proportion of the wood spirits, acetic acid, and other constituents of the latter. The charcoal remaining as a residue after the torrefication of the wood has also been placed in the Exhibition, to show its texture in each instance, some of the kinds being probably eligible as an ingredient for gunpowder. The quantities of potash have not been ascertained, as I intend to make it ere long a subject of special inquiry. In referring to the tables on these products of dry distillation, it must be remembered that the degree of heat to which the wood is subjected, as well as the degree of rapidity of its action, exercises a modifying influence on the results. Hence the percentage must be regarded as one of approximate calculation only; besides, wood of the same species from different climatic localities will not precisely give the same yield of products and educts. Mr. Hoffmann employed hydrochloric in preference to sulphuric acid in liberating the acetic acid from the lime, a process having several advantages (which here page 24 need not be pointed out), which largely compensates for the somewhat greater cost of that acid. It remains yet to refer, at least cursorily, to the uses to which the products of wood distillation find their principal application. Tar, so extensively needful for naval purposes, and for building structures, might in these southern countries, much more extensively than hitherto, be used for protecting ironworks exposed to the air against oxydation, the application of tar being less costly, more lasting, and often even more sightly, than that of oil-paint. Soft-wood, if coated with eucalyptus-tar, assumes an excellent appearance, and if in ornamental structures a touch of varnish is added, this tar becomes the most eligible article for securing duration. If the production of tar is to be the main object of secluded combustion of wood, the primitive Scandinavian means might be adopted, which involve but little more appliances than burning wood for coals.
The wood vinegar has its manifold applications. It serves for the fabrication of numerous kinds of articles for dyes, for special chemical purposes, and from it acetic acid may be obtained, or a rectified vinegar, applicable to culinary purposes. As Dye-Mordant, a solution of sesqui-acetate of alumina (the so-called red liquor) is largely used in calico printing. The sesqui-acetate and the simple acetate of iron are in quest to effect, connected with ferrocyanid of potassium, blue dyeing for woollen ware, and with various admixtures to produce avariety of colours in dyeing of cotton and silk. The simple acetate of iron yields, with madder (a plant like other dye-plants introduced into Victoria), a violet colour; and with the sesqui-acetate of alumina, brown and black dyes.
The chemical formula of the wood spirit is not identical with that of alcohol, but it is highly valuable as a solvent for resins in the preparation of varnish. It is but right to remark that a large factory, to which timber is floated on the Derwent, near Hobart Town, has commenced its distillation of wood within the last year; and that to Mr. Hugh Gray, of Ballarat, the credit is due of having, for the Exhibition of 1861, prepared tar and wood vinegar from a species of eucalypt, and of having given approximately the percentage. (Vide Jurors' Report, 1861, 20.)