The toxicity to fish of mixtures of poisons: II. Copper-ammonia and zinc-phenol mixtures

Tests with rainbow trout in mixtures of ammonium chloride with copper sulphate and of phenol with zinc sulphate have shown that the threshold of toxic concentration for a 50% mortality occurs in solutions for which a value of I is obtained by summing the concentrations of the individual poisons expressed as fractions of their individual threshold concentrations. With ammonia-copper mixtures this method of predicting the threshold concentration becomes progressively less adequate as lower percentage mortalities are considered.