jmoore

OK here goes. The fact you have used two types of unit ie metric and imperial (US imperial at that) and sometimes together is confusing and you lose something in the conversion, so here is how I have interpreted it.

You start with 3.9% active ingredient, which is equal to 39 g / l (grams per litre) stock solution.

You need 350 micromoles in your final solution or 0.05 g / l ( based on the relative molecular mass you supplied of 144.something)

To reach that figure you divide your final mass of 0.05 grams ( as we are talking about 1 litre) by your starting concentration of 39 g / l which gives a figure of 1.28 ml / litre.

I'm sorry, but I don't understand pounds per US gallon and get especially confused when talking about pints. I think you can ignore the inert material as it's inert. On the bottle does it give a concentration as a percentage of active ingredient or a concentration in ounces per gallon?

Hope this helps.