U of S | Mailing List Archive | alt-photo-process-l | Re: Bleach-development with gum recipe

Re: Bleach-development with gum recipe

Marek or John,
You are chemists, correct?

Well, when I check online here:

There is an interesting discussion of mixing a 0.5% bleach. 
Anyway, it talks of mixing a bleach with a powder, and to
get a 0.5% it is like 7g of powdered calcium hypochlorite,
etc. etc.  and that these powders are "chlorine releasing",
hence the discrepancy between a 7g/1000ml solution and the
percentage--in other words powders do not provide a "pure
bleach" gram per gram. Because I can't figure out how a 7g.
per liter makes a .5% bleach solution... 

I guarantee I am saying this wrong, but I bet you'll
understand and explain this to me?

I don't know if sodium hypochlorite or potassium are the
same way as calcium, but this would explain to me the
discrepancy between the recipe for Eau de Javel/Javelle
at 8g per 500ml from 1943 and
this 5% thing.  

Do you know any chemistry info on bleach powders you could
tell to shed light on this?

The reason I ask, is I think it may be important, then, if
this is the case--that powders provide less actual bleach
than, say, Chlorox does, to make sure to match the liquid
amount used to the original formula.  At the very least it
may explain why you, John, use a much more dilute form of
bleach than the recipe suggests, and Chlorox may contain
many more grams of powder than its "5%" suggests. In any
case, if there were an actual exact amount of modern day
liquid bleach to equate with the old powdered formula would
be comparing apples to apples.

John, do you have an old recipe from back then of how much
proprietary liquid Javelle water would have been used in a
liter? It  seems that the concentration of it was 5% at that

I don't know which form of hypochlorite was used,
though...but in the same article I think it says the sodium
form is 60% chlorine.


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