USES OF COAL TAR

Evening Star, Issue 19660, 13 September 1927, Page 5

USES OF COAL TAR

MULTITUDINOUS BY-PRODUCTS THE INDUSTRY IN HEW ZEALAND Time was wdien coal tar was so little used in manufacture that a very largo surplus of it was looked upon merely as a black, oily, evil-smelling mess which, owing to its alleged uselessness, was regarded as a nuisance. Nobody know what to do with it. It was the object of scientific contempt. Then came a great change. Men began to realise that research work was the soul of industrial prosperity, and as a result of subsequent experiments the coal tar industry is now recognised to be of fundamental importance, having been classified according to modern methods of nomenclature as a.“key industry.” Tho number of valuable products and by-products of coal tar arc now well nigh incalculable. Imagine a huge, thickly-branched tree as representing a diagram depicting coal far and its products. The lower part of the trank corresponds to the tar itself, and it is no exaggeration to say that lor every branch of tho tree, big or small, there is a product or a by-product. The first two main _ branches represent the innmonical oils and tho light oils. From tho latter emerge the hydro-carbons, benzol, the anilines, and the toluenes. An offshoot of the last-named, by tho way, is saecarhine, a well-known wartime substitute for sugar Speaking of warfare brings us to tho realisation that the toluenes give rise to the nitrotoluciio explosives, including the famous r On climbing further up tho trunk, we arrive at the heavy oil and naphthalene branches. _ Very closely allied with naphthalene is creosote oil. The remainder of tho treo trunk represents pitch. How many people know that from each of these main branches springs a network of subsidiary limbs symbolical of dyes, perfumes, photographic developers, and drugs (such as aspirin) with which they aro quite familiar? All things considered, it can readily bo understood that coal tar is a very wonderful substance. And to what extent is it utilised for manufacture in New Zealand?

This quest ion, put by a ‘Star* reporter, was answered by Mr Cl. W. Gibson, whose firm in Christchurch is at present making as many as twentyfour different predicts of coal tar. Mr Gibson stated that tar distillation had made a definite start in the dominion, and as tho industry developed other products would be added to tlio manufacturing list. Among tho products being turned out were some so well known that no description concerning them was necessary; these -included anti-corrosive paint (which was both waterproof and aeidproof), spraying oil for fruit trees, sheep dip, disinfectant fluid, carbolic powder and disinfectant blocks.

Among other articles being manufactured was solvent naphtha, which was the best-known solvent for rubber, ami was used extensively in that industry; heavy naphtha, another coal tar prowas often utilised as a turpentine substitute. Of particular interest was tho manufacture of naphthalene. J n tho process of sublimation naphthalene came over in the form of a gas, which gradually took the form of crystals when in contact with the air, and fell like a beautiful snowstorm. This substance was used largely for sprinkling on hides and skins. Moth halls were really little globes of compressed naphthalene. Additional products being manufactured in New Zealand were wood stains, branding paint for hides and sacks, marine glue, bottling wax, and liquid carbolic acid. Mr Gibson gavo some interesting information concerning wood preservatives. He explained that there were two methods of preserving timber—namely, immersion, and painting with a brush. if tho immersion process wore carried out, the timber, poles and posts for example, were dipped in a bath of creosote oil. if poles were being preserved, they were usually stood up in a bath of the liquid for a time long enough to allow them to soak up tho creosote until it penetrated by means of the natural pores right through tho wood. This method was extensively practised in America, and tho New Zealand Forestry Department was now doing a great deal of work in this connection. Also, it was trying to persaudo various power boards to employ creosote in preserving their poles, and farmers were being advised to treat their fencing posts in a similar manner. Mr David Miller, the Government entomologist, when addressing the Forestry League at Wellington last March, had given some interesting information regarding inscot wood borers. He stated that flic treatment of wood, even sapwood, with creosote would prevent not only borer attacks, but also decay. It was found that when creosote was applied warm its preservative powers had stood for twenty-five years. Although creosote oil could be applied to wood with a, brush, carbolineum, which was used in the second method of wood preserving, was bettor for this treatment; it was a heavier oil, and contained 2 per .cent , chlorine. In modern roadmaking distilled tar was finding great favor throughout the dominion. Mr Gibson explained that before crude tar could take effect there would liavo to Pe a certain amount of evaporation of water and acids; besides which a fifth of the binding power was lost. When applied to Now Zealand roads distilled tar was used _ either alone or in conjunction with bitumen. In connection with pitch, be stated that there were various finalities being made in the country. Electrical pitch, because it kept out moisture, was utilised extensively in connection with subterranean cables.