>Richard Sullivan wrote:
>>
>> I made a batch with my old favorite formula and got a heavy amount of
>> yellow precipitate in the bottom of the beaker.
<snip>
George Smythe replies:
>This is interesting and I'm wondering what combination of ingredients
>you were using. I've gotten a dark crud (so this may well be something
>completely different) after the solution has aged a bit. Leaving it in
>caused badly uneven development. Filtering it out made the difference.
If I can remember, I am at my home machine, so my formulary is not here.
90 gm ferric ammonium citrate
15 gm tartaric acid
30 gm silver nitrate
Mix each in 250 ml water
add 1 to 2 and add 3
Pretty simple. It is not just the pH of the solution that counts as there
is the tartaric acid in the mix already. My guess is that the yellow crud
is silver tartrate. An excess oxalic acid in Kallitypes causes a yellow
precipitate to form which is silver oxalate. What you are getting is more
than likely something else, my guess is that it is throwing off iron, or
iron oxide as ferric compounds are wont to do.
Dick Sullivan