86 KANSAS CI 7 Y REVIEW OF SCIENCE. 
tion commonly employed contains one pound of the salt to ten gallons of water, 
and is injected by steam pressure in a cylinder like that of Breant, The same 
limitations which apply to the copper sulphate seem also to hold good of the zinc 
chloride, the latter compound having the advantage of cheapness, and being 
nearly, if not quite as efficient a preservative. Burnettized wood was found to 
stand the Woolwich test as well as that which had been kyanized. In Germany 
the chloride has been applied successfully to railway sleepers, bridge timbers, 
and telegraph posts, and also to the wood-work in some of the Hartz mines. 
Furthermore, it has been successfully used for the protection of wooden pave- 
ments. 
One more preservative method remains to claim our attention, namely, that 
of creosoting. Bethell, in 1838, using a vacuum cylinder, injected into wood a 
preparation of coal-tar oil, known commercially as **gallotin." Since that time, 
peat and brown coal creosote, paraffine, pyroligneous acid, and the so-called 
"pyrolignite of iron," have been applied in the same way. The best of all the 
substances of this class, however, is the heavy oil or "dead oil" of coal-tar. 
That portion is chosen which boils at about 180° C, and depends, to a great 
extent, for its efficacy upon the phenol which it contains. This phenol coagu- 
lates the vegetable albumen, while the bituminous oils completely penetrate the 
capillaries of the wood, cover the fibres with an impervious coating, and protect 
them entirely from the action of water and air. BohP finds that the poorer the 
liquid is in oily matter the more readily it penetrates the wood. Since much of 
the creosote is easily washed out, he subsequently treats the wood with ferrous 
sulphate, in order to fix the preservative. Ferrous hydroxide is precipitated, 
which is gradually converted into the ferric hydroxide at the cost of such atmos- 
pheric oxygen and moisture as may have been retained in the wood. There are 
two main objections to the plan of creosoting timber. The first is that it is appli- 
cable only to winter-cut hard woods. In this respect it is just the reverse of the 
copper sulphate process. The latter protects green out not seasoned wood, the 
former preserves seasoned but not green wood (See the paper by Baist already 
cited). The second objection is based upon the amount of the preservative tO' 
be used. Lumber, properly treated, absorbs about eight pounds of the coal-tar 
oil to the cubic foot.^^ 
At present Bethell's process is largely used in England. For the preserva- 
tion of railway sleepers it is said to be employed to the total exclusion of all other 
processes. On the Buckinghamshire R. R. ninety thousand kyanized, burnett- 
ized, and payenized sleepers were laid down, with thirty thousand which had 
been creosoted, and the last proved the most durable. ^^ In the mines of Prussian 
Saxony, Upper Silesia, Thuringia, and Saarbruck, coal-tar for the protection of 
timber is preferred to the zinc chloride f^ and in an experiment by Price at Glou- 
cester, England, when unprepared wood decayed in a year, kyanized wood 
18 Dingl. Pol. Joxir., 144, 448, 1857. 
19 Sci. Amer., 3, 186, 1860. 
20 Engineering, 13, 30, 1872. 
