I'm working with earthworms and methylparaben and I have 20 buckets of soil that are to have different concentrations of paraben to be added, how do I calculate that using the weight of the soil?
The question is not clearly stated, but I believe you are trying to determine the concentration of methylparaben in the soil, such as mg MP / kg soil. Let's assume the soil is very homogenous and your mixing uniformly distributes the MP through the soil in each bucket. It is further assumed that you know the concentrations of MP in your solutions, you know the volume of each concentration added to the soil, and none of the MP volatilizes away.
Example:
You mix 10 mL of a 2 mg MP /mL solution into 10 kg of soil.