84 KAiVSAS CITY REVIEW OF SCIENCE. 
have been recommended by Volmeister, in 1798. It has some good effect, which 
is due partly, if not wholly, to its hygroscopic action. Examples of its efficacy 
may be found in many salt mines, whose timbers exhibit remarkable durability. 
Ships engaged in the salt trade remain sound, it is said, much longer than other 
vessels. But the best test of the preservative power of salt was made some time 
ago in Saxony. * Wood prepared with this substance was exposed side by side 
with some which was unprotected. The impregnated timber was perfectly sound 
at the end of thirteen years, while the other became unserviceable in two. 
At one time, corrosive sublimate was largely in vogue, but it is at present little 
used on account of its high cost, and its deleterious effects upon workmen. As a 
preservative of wood, it seems first to have been recommended by Knowles and 
Davy in 1821. Kyan, whence the term "kyanizing," introduced it in 1832. In 
1837 Letellier proposed to use it in connection with gelatin. The double chloride, 
HgCl2-|-KCl, (procured by the decomposition of carnallite with mercuric oxide^ 
has lately been used as a substitute. The corrosive sublimate is injected into the 
wood by steam power, the standard solution containing one pound of the salt to 
five gallons of water. Its value as a preservative agent is unquestionable. At 
Woolwich,^" pieces of kyanized and unkyanized wood were buried together in a 
trench. This trench was filled with putrefying vegetable matter and fragments of 
wood affected with dry rot, the whole being covered with horse-dung. At the 
end of five years, the protected wood was found to be unchanged; while that 
which was unprepared was seriously affected in one year. 
With regard to ferrous sulphate, statements disagree. It has had the tests of 
experience less thoroughly than some other more fashionable preservatives. It 
was recommended by Strutzlei in 1834, Earle in 1843, and Apeltin 1853. Bohl, 
whose results will be considered in another connection, has employed it simul- 
taneously with creosote. Its mode of action is rather complex. Injected into 
wood, it finds enclosed there a certain quantity of atmospheric air The oxygen 
of this air is soon absorbed by the ferrous sulphate, basic sulphate and some ferric 
oxide resulting from the change. On one hand, it is said that this action is bene- 
ficial. The fibre of the wood becomes coated with mineral matter, and is so 
protected from decay. In opposition, it is urged that the wood is weakened by 
this reaction, and that it is far less completely protected from decay than by some 
other more familiar processes. 
Copper sulphate — blue vitriol — must pass for one of the very best of the pre- 
servatives of wood. Its merits have been tested quite thoroughly, and some occa 
sional failures in its action have been satisfactorily explained. Boucherie, who 
made experiments with a number of antiseptics, after getting poor results with 
salts of lead and iron, finally settled upon this agent as the best of all, and time 
has in many respects justified his decision. At first Boucherie impregnated the 
wood by the process of suction, which we have already considered, but finally 
8 Dingl. Pol. Jour. 202, 174, 1871. 
9 Wagner's Chemical Technology 
10 Parnell's Applied Chemistry. 
