Question

If a soluble chemical is mixed into water, does that chemical lose its specific gravity?

The question that was asked to me was when calculating for dosage rates in water treatment, why is the weight of water (8.34 lbs/gal) used instead of the weight of the chemical (specific gravity). I first said because you're treating the water, not the chemical. I also said, because the chemical (ferric sulfate, for instance) is a solute. Then I asked myself the above mentioned question and realized I didn't know if I was right to say that.

Please help.

Answer 1

Well, You are almost right about it. It's not that the chemical lose it's specific gravity, remember the definition of specific gravity which is the ratio of the mass of a material to that of an equal volume of water. This is pretty close and similar to the definition of density, and density of water is 1 g/mL. So the thing that happen here is that the solute is mixing with the solvent, which has a higher density and it's in great amounts, so it's like you're mixing the specif gravities (or density if you like) to make a new one, but the higher contribution would be done by the water. That's why you use the weight of water the most. You can add this to your explanation too.

Tell me in a comment if this works, or need something to be explained better or something to be fixed.

Hope this helps