In 1779, M. Pallas, in Russia, proposed to steep wood in _sulphate of iron_ (green vitriol) until it had penetrated deeply, _and_ then in _lime_ to precipitate the vitriol. Neumann, in his first volume of ‘Chemistry,’ on the article green vitriol, says, “That in the Swedish transactions this salt is recommended for preserving wood, particularly the wheels of carriages, from decay.
“When all the pieces are fit for being joined together, they are directed to be boiled in a solution of vitriol for three or four hours, and then kept for some days in a warm place to dry. It is said that the wood by this preparation becomes so hard and compact that moisture cannot penetrate it, and that iron nails are not so apt to be destroyed in this vitriolated wood as might be expected, _but last as long as the wood itself_.”
In 1780 the marcasite termed by the miners _mundic_, found in great abundance in the tin mines in Devonshire and Cornwall, was employed, in a state of fusion, to eradicate present and to prevent the future growth of dry rot; but whether its efficacy was proved by time is not known. A garden walk where there are some pieces of mundic never has any weeds growing; the rain that falls becomes impregnated with its qualities, and in flowing through the walk prevents vegetation.
In 1796 Hales proposed to _creosote_ the treenails of ships: this was forty-two years previous to Bethell’s patent for creosoting wood.
About the year 1800, the Society of Arts’ building in the Adelphi, London, being attacked by dry rot, Dr. Higgins examined the timbers, caused some to be removed and replaced by new, and the remainder to be scraped and washed with a solution of _caustic ammonia_, so as by burning the surface of the wood to prevent the growth of fungi.
At the commencement of the present century, a member of the Royal Academy of Stockholm called attention to the use of _alum_ for preserving wood from fire. He says, in the Memoirs of that Academy, “Having been within these few years to visit the alum mines of Loswers, in the province of Calmar, I took notice of some attempts made to burn the old staves of tubs and pails that had been used for the alum works. For this purpose they were thrown into the furnace, but those pieces of wood which had been _penetrated_ by the alum did not burn, though they remained for a long time in the fire, where they only became red; however, at last they were consumed by the intenseness of the heat, but they yielded no flame.” He concludes, from this experiment, that wood or timber for the purpose of building may be secured against the action of fire by letting it remain for some time in water wherein vitriol, alum, or any other salt has been dissolved which contains no inflammable parts.