Civil Engineering Reference
In-Depth Information
Table 19.3:
Poisons used for impregnation
Type
Fungicide
Insecticide
Level of
poison
Mineral:
Zinc salts
x
x
Medium
Arsenic salts
x
High
Chromium salts
x
x
Medium
Fluorine salts
x
Medium
Copper salts
x
Medium
Potassium ferric sulphate
x
Low
Potassium aluminium sulphate
x
Low
Borax and boric acid
x
x
Low
Aluminium sulphate
x
Low
Ferrous sulphate
x
x
Low
Lye from soda or potash
(1)
x
Low
Oil- and coal-based:
Creosote
x
High
Carbolineum
x
High
Pentachlorophenol
x
High
Hexachlorobenzene
x
High
Pyrethrin
x
Medium
Xylidene
x
Medium
Endosulphane
x
Medium
Tributyltin
x
High
Parathion
x
High
Discofluamide
x
Medium
Tolufluamide
x
Medium
Plant-based:
Wood tar:
from softwood
x
Medium
from beech
x
Low
Extract from bark
x
Low
Wood vinegar (for treating
already attacked wood)
x
x
Low
Note:
(1) Potash lye can be prepared from wood ashes.
preferably the strongest. This rationalizes production for manufacturers, but at
the same time involves considerable 'over-impregnation'. A strong impregnating
agent usually contains all three substances: arsenic, copper and chrome. For tim-
ber above ground level it is quite adequate just to use copper.
Both metal salts and oil products have very restricted resources.
