Lethal concentrations of common heavy metals and salt. Compiled from 1996 EPA quotations.

MERCURY	0.0005 mg/l	You will need to dilute cup F 4 more times.
SILVER	0.005 mg/l	You will need to dilute cup F 3 more times
IRON	1.0 mg/l	Cup F - 1 ppm
NaCl (Salt)	200.0 mg/l	200 ppm = 1/5 of a gram
		(1 gram mass of a small paper clip)

Think About It!

1. Does a dissolved toxin ever disappear? Completely?

2. If 50% of the population of the organism you studied was killed, how might that affect the ecosystem?

3. When the color disappeared from the cups, was there any colored solution still in the cup?

4. Is dilution the solution to pollution? Be specific. If we just keep adding water to toxins, will the organisms be safe?