I'm not sure if this is the right place to post this, but here goes. Could someone please explain to me how I can calculate the amount of grams or milligrams per liter there would be of a specific element or compound, by looking at the compound it is contained in, the weight of that compound and its dilution? For example, if 40 grams of potassium ferricyanide is dissolved in one liter of water, how would I calculate the amount in grams per liter of cyanide in that solution? Same for chromium where the dissolved salt is potassium dichromate. Apart from those examples, I'm really interested in the methodology, which I assume has something to do with molecular weights - and where to find the needed data - so I can also work on other examples.

This all has to do with my getting my mind around some environmental rules and how best to deal with them.

Many thanks.