Diluting a Dilution?

[Bruce Osgood]

I'm working with a paper developer that calls for 30cc of a 1% solution of Benzotriazole in two liters of Stock Solution. I've done that and have about 1800 mL of Working solution in the tray that is Stock diluted 1 + 3.

I would like to experiment with additional Benzo, perhaps at a rate of 30cc of 2% or twice the potency.

Can I add an amount of Benzo to the Working/tray solution and mix it in? Will it dissolve? Should the Working solution be heated to do so? What would be a good amount to add?

Or should I simply make a new batch of Stock solution?

Thank you,

 

[pgomena]

30ml is such a small amount I would use twice the amount you added before to achieve 2%. You are not increasing the total volume by a significant amount.

Peter Gomena

 

[snallan]

I would add the additional benzotriazole straight to the working solution.

30cc of 2% added to the stock would be 60cc of the 1%, so you need an additional 30cc of your 1% benzotriazole soln. As your stock is diluted 1+3 to give the working solution, you will need 30/4 = 7.5cc of the benzotriazole added to the working solution for the effect of twice the amount.

Indeed, in a situation like this, I might be tempted to make up the stock solution without benzotriazole in the first place, and add the required amount to the working solution when I was making it up. Yes this adds an additional step when preparing the working solution, but I often prefer the flexibility.

 

[Bruce Osgood]

I would add the additional benzotriazole straight to the working solution.

Indeed, in a situation like this, I might be tempted to make up the stock solution without benzotriazole in the first place, and add the required amount to the working solution when I was making it up. Yes this adds an additional step when preparing the working solution, but I often prefer the flexibility.

I think you are absolutely right and that's what I'm going to do; thank you both.