METHODS OF INJECTION, 671 



that of several tropical woods. The softened wood is then rolled 

 and pressed till it is reduced in thickness by 10% or even 40% 

 The effect of the injection is thus increased by compressing the 

 wood, and a very superior kind of furniture-wood is thus produced 

 (Exner). It is preferable to use freshly felled wood, and Exner 

 states that beechwood thus injected and compressed gains up 

 to 19% in strength. 



(c) Steeping converted wood in antiseptic liquids. — This 

 method is chiefly employed for Kyauisiiui stakes and small 

 pieces of wood. Large wooden troughs like cooling-troughs are 

 parti}' filled with a solution* of corrosive sublimate in water, 

 the pieces of wood are placed in them, weighted to make them 

 sink and kept from 8 to 10 days immersed. Stakes are merely 

 placed in petroleum casks tilled with blue vitriol solution and 

 other antiseptic liquids. 



[Boulton says that small pieces of wood, hop-poles, fencing-slabs, 

 stakes, tkc, may be placed in an open trough with heavy tar-oil, 

 which is heated by a fire under the trough, care being taken not to 

 raise the temperature of the creosote above 230° F. — Tr.J 



Other methods by immersion give inferior results. Formerly 

 the wood was frequently boiled in antiseptic liquids, steam being 

 introduced into the vessel in which the wood was immersed 

 until the liquid in it boiled. Blue vitriol, borax solution, kc, 

 were thus injected, but the liquid must be kept at the boiling 

 point for 10 or 12 hours. 



H. Liebau, in Magdeburg, has recently attempted to introduce 

 the liquid from the interior of the pieces of wood instead of 

 externally, in order to protect the heartwood from decay. This 

 can be used only for stakes, piles, &c., the axis of which is bored 

 through after they have been driven into the ground and tar-oil, 

 pitch, &c., poured into the cavity. Nothing can yet be said as 

 to the efficacy of this method. 



[Boppe states t that in France mining pit-props are immersed for 

 about 24 hours in solutions of Hlbs. per gallon (1.50 gr. to 1 liter) of 

 sulphate of iron, or in wood-tar heated to a temperature of 278° F. 



* Accordiiif^toTredgold's Carpentry by Hurst, 1871, lib. of corrosive sublimate 

 to 10 to 15 gals, of water, iMbs. of the sublimate in the strongest solution being 

 enough for a load or 50 cubic feet of wood. — Tp..] 



t Techuologie Forestiere, p. 97- 



