so Im in possession of a substance that is active at about 500 micro grams. The substance is soluble in water. Now I have about ten milligrams of said substance but no means of precise measurement. Is there a reliable way to come up with a approximate liquid dose? Like for example, dissolve X mg for every X ml of water and then put into a visine or nose spray bottle where each drop/spray could be equal to an approximate dose?

Technically if you dissolve 10mg in 10ml of liquid then you would have 1 mg per 1 ml.

Just do the math to come up with the correct dosage level and liquid amount.

10mg in 100 ml 1mg per 10ml. So on...

If I had 10mg of such a substance, I'd invest in one of these.

I could dilute the 10mg to the level you please, and then measure out 500mcg aliquots whenever you choose.

An example: Get a 1-10 microliter pipetman, dissolve 10mg into 20 microliters of water (if possible), and then you could accurately parcel out 500 mcg quantities by 1 microliter dots. (Or dissolve in 100 microliters, and get 100 mcg in 1 microliter dots).

Or get a 20-100, dissolve the 10mg into 400 microliters, and parcel out 500 mcg quantities by 20 microliter dots.