]2 
On the Preservation of Timber. 
in 1838, has been more generally used, for it possesses the great 
collateral advantage of being a disinfecting agent, for which pur- 
pose it is now very extensively employed in France. 
Chloride of Manganese. — Le Gros has substituted the waste 
acid chloride of manganese, which runs from the stills of the 
manufacturers of bleaching-powder, and he neutralizes the excess 
of acid by oxide of zinc, which precipitates the ferruginous mat- 
ters. This double chloride of manganese and zinc ought to be 
an excellent compound, but I do not know whether it has been 
much employed. 
Sulphate of Copper. Pyrolignate of Iron. — The sulphate of 
copper appears to be in fashion at the present time, having been 
introduced by Boucherie, in connection with his new apparatus. 
I find it first named in the patent list, by Margary, in 1837. 
Boucherie was at first inclined to give the preference to the crude 
pyrolignate of iron, which he says combines many advantages, as 
its oxide forms stable compounds with nearly all organic sub- 
stances, its acid being without corrosive action and volatile, while 
it contains the largest quantity of creosote which an aqueous 
solution can dissolve. 
Sulphates of Iron and Zinc. — The use of sulphate of iron was 
also proposed by Bethell in his patent of 1838, and in some 
situations, as in copperas beds, its preservative action has been 
strongly shown ; but it has been objected that it will destroy 
wood by the liberation of its acid, either under the influence of 
oxidation, or the combination of its oxide with the organic sub- 
stances. This objection does not hold good against the sulphates 
of copper and zinc, and which objection M. Breant has attempted 
to obviate in the case of any metallic sulphate, by introducing 
linseed-oil into the wood, previously injected with these salts. 
Acetate of Lead. — Acetate of lead is also an excellent material, 
as its oxide forms insoluble and non-putrescent compounds with 
numerous organic substances, while its acid is volatile and not 
corrosive. The crude sugar of lead would also possess the same 
advantages as the pyrolignate of iron, in containing a large pro- 
portion of creosote. 
Arsenious Acid. — Similar in its action to the preceding bodies 
is white arsenic, or arsenious acid, the use of which was patented 
by Verner in 1849, and by Romaine in 1853, who employs a 
boiling liquid of oil and gas-tar, with cream of lime, and sug- 
gests the addition of arsenic to protect the wood against the 
attack of the white ant in the East and West Indies. The great 
danger, however, which attends its application is at once fatal to 
its general use. 
Class IX. Filling the pores of the Wood. — This division of 
chemical compounds embraces another object, namely, the filling 
