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tbeir ties, use this antiseptic might be accepted as a proof of its effi- 
ciency as a preservative. 
(4) Sulphate of Copper, — Sulphate of copper (blue vitriol) had long 
been known as a strong antiseptic ; but was first used for t he preserva- 
tion of wood by Boucherie, in the year 1838. When used for this pur- 
pose it should be tree from deleterious admixtures, among which the 
most common, and at the same time most injurious to wood, is sulphate 
of iron; for sulphate of iron is easily decomposed, and the free sul- 
phuric acid resulting therefrom attacks and weakens the wood fiber. 
The solution of sulphate of copper recommended by Boucherie con- 
sisted of 1 part (by weight) of sulphate of copper to 100 parts (by 
weight) of water. 
The increase of timber in weight by impregnation with sulphate of 
copper was found by Boucherie, when his method of treatment was 
used, to be as follows per 100 cubic feet : pine, 140 pounds ; oak, 145 
pounds; Hemlock, 320 pounds; Beech, 540 pounds. 
But this increase in weight does not express the weight of dry sul- 
phate of copper taken up by the wood, nor the weight of the diluted 
solution of sulphate of copper absorbed.* The weight of dry sulphate 
of copper absorbed by Beech found to be 32 pounds in 100 cubic 
feet of wood, and this is the weight of dry sulphate of copper which 
100 cubic feet of this kind of wood is required to contain (1.1 pounds 
per tie of 3.5 cubic feet), under the specifications of the French engineers. 
When the Boucherie process of impregnation is used, the weight of 
sulphate of copper required per cubic foot may be set down at 40 pounds 
per 100 cubic feet, to make allowance for loss in antiseptic resulting 
from his mode of treatment. Impregnation with solutions of sulphate 
of copper has been carried on by almost every known method of treat- 
ment, viz: by steeping, by the Boucherie process, and by vacuum and 
pressure. 
One disadvantage in the use of this antiseptic consists in the fact 
that boilers, pipes, pumps, and tools used in carryiug on the process 
must consist of copper, because contact with iron decomposes the sul- 
phate of copper. This, of course, largely increases the cost of the 
necessary plant. 
Another respect in which treatment with sulphate of copper is interior 
to treatment with chloride of zinc, at least in preserving railroad ties, 
may be found in the fact, that wdien ties treated with sulphate of cop- 
per are placed in the track, the iron rails and spikes coming into contact 
with the sulphate of copper will decompose the latter, producing free 
sulphuric acid, w T hich attacks the liber and injures the strength of the 
timber. Jn some cases the endeavor has been made to prevent this by 
* Boucherie found that in 2.1 hours 3,060 liters of solution entered into a Beech log 
15 meters long and averaging 0.0 meters in diameter, or abput i of its total volume. 
