196 Processes for Wood-preservation. 



acid. It is less adapted to dry wood than to that newly cut, if, in- 

 deed, it is not limited to the latter. 1 



776. It is found that the sulphate of copper penetrates with great 

 difficulty into oak, the ends only absorbing to some extent along the 

 spongy layers of the spring growth, while the hard layers of wood 

 formed later in the season do not absorb the least. Elm will absorb 

 very well, excepting in the close firm knots. Beech will admit of 

 very complete penetration in every part. Pine will absorb only in 

 the sap wood. Locust wholly resists penetration. Ash is in about 

 the same class with oak, and so is the chestnut. Birch, when sea- 

 soned, may be prepared very well, and poplar the most completely 

 of all. 



777. The Burnett Process. This was first brought to notice be- 

 tween the years 1838 and 1840 by Sir William Burnett, formerly 

 Director General of the Medical Department of the British Navy. 

 It consists in an injection of the chloride of zinc, at the rate of 1 

 pound to 9 or 10 gallons of water, under a pressure of 150 pounds 

 to the inch. This salt, although soluble, does not easily come out 

 when exposed to the weather or buried in the ground. It is claimed 

 to render wood uninflammable. The cost is about 6 to 8 cents a cubic 

 foot. Extensive works have been constructed for the preparation of 

 wood by this process, and very favorable testimonials have been of- 

 fered in its favor. A concentrated solution is sold at 5s. per gallon 

 in London, to be diluted with 40 gallons of water for use by this 

 process, with instructions and license to use. 



778. By Carey's Process (1829), a mixture of salt powdered char- 

 coal and animal or vegetable oil is introduced into timber by holes 

 in various parts, and the holes are then closed. Various patents 

 have been granted for inserting preservative substances in the wood, 

 such as coal tar and pulverized mineral substances, more or less 

 soluble and antiseptic in their nature. 



779. TJie Hatzfeld Process. From the fact that oak timbers buried 

 in contact with ochres and the salts of iron acquire great durability, 

 apparently from the reaction between the tannin of the wood and 

 iron, Mr. H. proposes to inject various woods with tannic acid, and 

 then with the pyrolignite of iron, thus assimilating the wood to the 



1 Baist, in Dinner's Polytechnic Journal, 1801, Vol. 162, p. 397. See ib., 

 1851, Vol. 120, p. 140; 123, p. 223. 



