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1. I like to keep a potassium bromide solution around for a number of purposes. I would just weigh your large crystals, make the 10% solution and use it as you need. It will last forever. Then you can use it to mix developers of all kinds, as well as as a restrainer-additive for your print developer and as a component of a rehalogenating bleach together with a potassium ferricyanide solution.

Best,

Doremus

www.DoremusScudder.com

2. So, just to clarify for people like me (gave up mathematics and chemistry age 14, find ratios difficult to grasp sometimes, has to calculate the dilution on a scrap of paper each time I make up some developer) ...

10g/l = 1% solution
100g/l = 10% solution
200g/l = 20% solution ... and so on, up to the solubility limit of KBr in water I presume.

SO, when I am making up a litre of developer that requires 1g of KBr per litre, I would substitute 100ml of a 10% solution for 100ml of the total volume of water required by the formula ?

(I imagine a lot of sighing, eye rolling and shaking of heads from all the scientificky types at this point)

3. Originally Posted by pdeeh
So, just to clarify for people like me (gave up mathematics and chemistry age 14, find ratios difficult to grasp sometimes, has to calculate the dilution on a scrap of paper each time I make up some developer) ...

{snip}

(I imagine a lot of sighing, eye rolling and shaking of heads from all the scientificky types at this point)
You aren't the only one who isn't mathematically inclined. While I would like to try some of the home brewed chemicals, I limit myself to the stuff that's pre-mixed/portioned, precisely so I don't have to calculate anything. Math and me do not get along, so don't worry about you being alone.

4. So..wait a minute. Still not getting it.

5. Originally Posted by pdeeh
So, just to clarify for people like me (gave up mathematics and chemistry age 14, find ratios difficult to grasp sometimes, has to calculate the dilution on a scrap of paper each time I make up some developer) ...

10g/l = 1% solution
100g/l = 10% solution
200g/l = 20% solution ... and so on, up to the solubility limit of KBr in water I presume.

SO, when I am making up a litre of developer that requires 1g of KBr per litre, I would substitute 100ml of a 10% solution for 100ml of the total volume of water required by the formula ?

(I imagine a lot of sighing, eye rolling and shaking of heads from all the scientificky types at this point)
Yes - this is correct!

6. Hurrah!

7. Originally Posted by pdeeh
So, just to clarify for people like me (gave up mathematics and chemistry age 14, find ratios difficult to grasp sometimes, has to calculate the dilution on a scrap of paper each time I make up some developer) ...

10g/l = 1% solution
100g/l = 10% solution
200g/l = 20% solution ... and so on, up to the solubility limit of KBr in water I presume.

SO, when I am making up a litre of developer that requires 1g of KBr per litre, I would substitute 100ml of a 10% solution for 100ml of the total volume of water required by the formula ?

(I imagine a lot of sighing, eye rolling and shaking of heads from all the scientificky types at this point)
No quite 100ml. You see, 100ml of 10% solution contains exactly 10g of KBr. If you need 1g, you use 1/10th of it, or 10ml, not 100.

Think of it in terms of bromide in the bottle. Say you dissolved 100g of KBr in some amount of water. If a formula calls for 50g of KBr, you use half of the solution, if a formula calls for 1g, you use 1/100ths of the solution, 5g - 5/100ths, etc.

8. thank you for the (completely obvious now you point it out) correction

Really, it's a wonder sometimes that I've managed to develop any film or prints at all, or even make a cup of tea. Although I suppose making tea doesn't require the ability to divide by 10 correctly.

jeez

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