Abstract
Acute toxicity and its stability of the spent chlorination liquor (SCL) of multi-stage kraft bleaching was examined using a fish (Oryzias latipes) as the test orgainsm. Both red pine (Pinus densiflora) and white birch (Betula platy phylla) were used as wood species representing soft and hard wood species. Results have been summarised as follows :
1) The toxicity of SCLs was labile to alkali treatment, and the lime treatment could be recommended.
2) The heating and the ultraviolet irradiation of SCL under acidic condition were not effective to reduce their acute toxicity. On the contrary, the heating increased the toxicity of SCL indicating the formation of new toxicant (s).
3) The diethyl ether extract yields of treated SCLs varied with the treatments, but there were no constant relationship to toxicity.
4) The tri-or tetrachloro-guaiacol and their catechol anlogs might not be the main toxicants of SCL.
