In 1841, a German, named Müenzing, a chemist of Heibronn, proposed _chloride of manganese_ (waste liquor in the manufacture of bleaching powder) as a preservative against dry rot in timber; but his process has not been adopted in England, and very little noticed abroad.
In July, 1841, Mr. Payne patented his invention for _sulphate of iron_ in London; and in June and November, 1846, in France; and in 1846 in London, for _carbonate of soda_.[13] The materials employed in Payne’s process are sulphate of iron and sulphate of lime, both being held in solution with water. The timber is placed in a cylinder in which a vacuum is formed by the condensation of steam, assisted by air pumps; a solution of sulphate of iron is then admitted into the vessel, which instantly insinuates itself into all the pores of the wood, previously freed from air by the vacuum, and, after about a minute’s exposure, impregnates its entire substance; the _sulphate of iron_ is then withdrawn, and another solution of _sulphate of lime_ thrown in, which enters the substance of the wood in the same manner as the former solution, and the two salts react upon each other, and form two new combinations within the substance of the wood--muriate of iron, and muriate of lime. One of the most valuable properties of timber thus prepared is its perfect incombustibility: when exposed to the action of flame or strong heat, it simply smoulders, and emits no flame. We may also reasonably infer that with such a compound in its pores, decay must be greatly retarded, and the liability to worms lessened, if not prevented. The greatest drawback consists in the increased difficulty of working. This invention has been approved by the Commissioners of Woods and Forests, and has received much approbation from the architectural profession. Mr. Hawkshaw, C.E., considers that this process renders wood brittle. It was employed for rendering wood uninflammable in the Houses of Parliament (we presume, in the carcase; for _steaming_ was used for the joiner’s work), British Museum, and other public buildings; and also for the Royal Stables at Claremont.
In 1842, Mr. Bethell stated before the Institute of Civil Engineers, London, that _silicate of potash_, or _soluble glass_, rendered wood uninflammable.