132 Experiments on Staining Wood . 
III. Distilled verdigris dissolved in vinegar stained 
wood green, but the colour could never be brought to a 
grass green. 
IV. Wood which has lain a long time under water be- 
comes black, as experience shows, and looks as if char- 
red. It, however, loses none of its toughness or com- 
pactness; and many trees dug up in Holland from the 
turf earth are employed there for ship-building. This 
effect of the sulphuric acid on wood gave occasion to the 
following experiment. Pieces of different kinds of wood, 
of considerable thickness, were placed in the sulphurous 
acid. In half an hour the whole surface of them was co 
vered with a yellowish scurf, and the wood itself had the 
appearance of being charred. When washed in water, 
and exposed some hours to the open air, it was observed 
that the black colour had penetrated still farther, that the 
interior part only retained the natural colour, and that the 
wood was exceedingly close and compact. After this 
wood had been several times rubbed over with the oil or 
spirit of turpentine, it became harder and firmer, so that 
it could receive the highest polish ; by which means the 
colour was rendered more agreeable. This process may 
be readily employed by artists, as it is easy, and does not 
require much expense. 
V. Another black dye for staining wood, which suc- 
ceeds extremely well, and may lead to other useful expe- 
riments, is that formed with liver of sulphur (sulphuret 
of potash) and metallic solutions. As the sulphurized 
hydrogen gas is so subtle that it penetrates the closest bo- 
dies, it might readily be conjectured that it would easily 
give a black colour to wood, if the latter could any how 
be made to imbibe it with a metallic solution. Pieces of 
different kinds of wood were placed, for several days suc- 
cessively, in a solution of acetite of lead, and a solution 
of silver, copper, iron, and other metals ; after which a 
