776
LIGNITE.
ferment with leaven. This dough is worked up with a sufficient quantity of waterform a bath for the skins, in which they are soaked for 48 hours ; they are then trans-ferred into small tubs, where they remain during fifteen days, after which they are washeat the river. These operations serve to prepare the skins for absorbing the astringj®juices with uniformity. A decoction of willow bark {salix ciuerea and salix caprea ) bing made, the skins are immersed in the boiler whenever the temperature of the liquorsufficiently lowered not to injure the animal fibres, and handled and pressed for half ?hour. This manipulation is repeated twice daily during the period of a week. ftanning infusion is then renewed, and applied to the same skins for another week; at . ^which, being exposed to the air to dry, they are ready for being dyed, and then currl ^ 8with the empyreumatic oil of the bark of the birch tree. To this substance the R us .leather owes its peculiarities. Many modes have been prescribed for preparing it > 0the following is the one practised in Russia .
The whitish membranous epidermis of the birch, stripped of all woody parts, is i®..duced into an iron boiler, which, when stullcd full, is covered tight with a vaulted iron J* jhaving a pipe rising from its centre. A second boiler into which this pipe passes "'ith°reaching its bottom, is set over the first, and is luted to it at the edges, after the twobolted together. They are then inverted, so that the upper one contains the birch bar •The under half of this apparatus is sunk in the earth, the surface of the upper boil elcoated over with a clay lute, then surrounded with a fire of wood, and exposed to a iheat, till the distillation be completed. This operation, though rude in appearance, a ,wasteful of wood, answers its purpose perfectly well. The iron cylinder apparatusin Britain for distilling wood vinegar, would, however, be much more convenientductive. When the above boilers are unluted, there is found in the upper one a very hrpowder of charcoal, and in the under one which served as a receiver, there is an Dbrown, empyreumatic fluid, of a very strong smell, which is mixed with the tar, and W J ((Jfloats over a small quantity of crude vinegar. The former matter is the oil employ eimpregnate the skins, by working it into the flesh side with the currier’s tools, it 15 jcult to make this oil penetrate with uniformity; and the Russians do not always sue 6 jin this process, for they turn out many skins in a spotted state. This oil is at l’ ieS ’obtained in France by distilling the birch bark in copper stills, and condensing th e 1ducts by means of a pipe plunged in cold water. About (10 per cent, of the weig 1the bark is extracted. j ;eB
The skins imbibe this oil most equally before they are fully dry. Care must be.* 1 (i ynot to apply too much of it, for fear of its passing through and staining the grain sithe leather. Clievreul has investigated the chemical nature of this odoriferous substaand finding it to be a peculiar compound, has called it betulinc. ■ atf: ,
LEDUM PALUSl'RE. This plant is employed in Russia to tan the skins ofcalves, and sheep, into a reddish leather of an agreeable smell; as also in the preparof the oil of birch, for mailing what is commonly called Russia leather. inoU s
LEGUM1NE is the name of a vegeto-alkali supposed to exist in legit®plants.
LEMONS. See Citric Acid , and Oils, Essential. , l0 *
LEVIGATION is the mechanical process whereby hard substances are reducevery fine powder. ,. p0 t-
LEUC1TE is a hard Vesuvian mineral, consisting of silica, 54 ; alumina, * <ash, 23. s ulp htt "
LEUCINE is a white crystalline substance produced by acting upon flesh witnric acid.
LEWIS is the name of one kind of shears used in cropping woollen cloth. ;he
LIAS is a fine-grained argillaceous limestone, whose geological position is uoolite; it is the proper lithographic stone. , i wi 1 ' 1
LIBAVIUS , Liquor of, is the bichloride of tin, prepared by dissolving that ,n p inar iatethe aid of heat, in aqua regia, or by passing chlorine gas through a solution o ^ cr ys-of tin till no more gas be absorbed, evaporating the solution, and setting it aS, . 0S jye sub-tallize. The anhydrous bichloride is best prepared by mixing four parts °f CUII cul -y as t0limate with one part of tin, previously amalgamated with just so much ®ei c( j u rle sSrender it pulverizable; and by distilling this mixture with a gentle heat. s 0 vcr-fluid, the dry bichloride of tin, or the proper fuming liquor of Libavius , co ^ ^ firs 1When it is mixed with one third of its weight of water it becomes sola -bichloride of tin is used in calico-printing.
LICHEN. SeeAucHiL.
LIGNEOUS MATTER is vegetable fibre. See Fibrous Matter.