85 
MiyniODS AND SUBSTANCES CTBEti tO KKTA1N ANTISEPTICS. 
The heavy oil of tar, being insoluble in water, will oof be removed 
from timber which has been impregnated with it, even if the limber is 
permanently submerged in water. But the metallic salts at present 
used in wood preservation, bichloride of mercury, chloride of zinc, and 
Sulphate of copper, being injected into the wood in the form of aqueous 
solutions, are of course liable to be dissolved again by moisture ami 
eventually to be removed when the timber is exposed to the action of 
water. Experiments made by chemists seem to prove that a portion 
at least of the sulphate of copper and of chloride of zinc combines with 
the liber of the wood and cannot be removed again; but all that has 
not been fixed by such combinat ion may, in the course of time, be re- 
moved from the wood when permanently immersed in water. Metallic 
salts should, therefore, not be used when wood is exposed to the con- 
stant action of water, and it would be desirable to adopt means forpre- 
venting even the gradual, but much slower, removal of the salts by rain 
and moist air, although the favorable results with wood which had not 
received such extra protection leaves some doubt as regards its eco- 
nomical value. 
The methods which are now used for preventing the " washing out 7 ' 
of the metal salts arc: (1) The'Thilmany process; (a) with sulphate of 
copper; (b) with sulphate of zinc. (2) The Wellhouse process. (3) 
The zinc gypsum process. (4) The zinc-creosote process. 
1. The Thilmcmy Process. — Thilmany, in 1809, took out a patent for a 
method of preservation by which the wood was first to be impregnated 
with sulphate of copper and then to be immersed in a bath of chloride 
of barium. An interchange of the constituents of these two salts, if 
brought together in the proper proportions, would leave the timber im- 
pregnated with chloride of copper and sulphate of barium, which latter, 
being insoluble in water and in all acids, was expected to fill up the 
pores of the wood so as to prevent the removal of the chloride of copper 
by water entering from the outside. 
The process was first tried at Cleveland, Ohio, with blocks for wood 
pavement. As far as I am informed, the wood was treated with sul- 
phate of copper by the Boucherie process and then immersed in a bath 
of chloride of barium. In 1881 I took up and examined some of the 
elm-wood blocks which had been thus treated and laid dowu in Saint 
Clair street in 1870, and found them perfectly sound after eleven years' 
exposure on the street. 
Works were erected at Defiance and Milwaukee, where the timber and 
t ies were treated with the Thilmany preservatives by steaming, vacuum, 
and pressure. But the results were not very favorable. At Defiance a 
solution of 1.5 in 10(),and later one of 2 in 100, was injected with a pressure 
of 80 to LOO pounds until all the pores of the wood (as Mr. Thilmany 
says) were charged with the solution, when the boiler was filled with a 
