[Rose911]

It has been a long time since I have had to do dilutions and I am struggling.

I am mixing a protein in PBS which has to be incubated with 0.1mM silver nitrate. I understand this amount is extremely small therefore I have to do a dilution (which I will do in PBS).

I need to calculate a reasonable amount of silver nitrate to use as I only have a small amount to use and don’t want to get it wrong.

I am going to add 8mg of protein to 20ml of PBS therefore I need to work backwards with my dilutions to figure out the amount of solution I will take from my final dilution?

Someone please help? 

[Arkcon]

You're really going to have to try and express your question more simply, and more completely.  I'm guessing you need a final concentration of 0.1 N AgNO₃.  You will have a 20 ml final volume.  Do you have solid silver nitrate, or a concentrated solution? 

At any rate, you know the definition of milimolar, right?  If you don't have it handy, you know the definition of molar, and molarity right?  You have some mathematical division to do, if you want to start from that.