U of S | Mailing List Archive | alt-photo-process-l | Re: Bleach Development with Gum

Re: Bleach Development with Gum

as you called me into question I cannot retreat...
Maybe there is someone already working with hypochlorides and more skilled than me, however:
1) the "active chlorine" is the amount (mass) of chlorine gas that can be released reacting with hydrochloric acid, that is double the amount of chlorine in the hypochloride.
2) for pure substances, the active chlorine content as defined above is:
99% for calcium hypochloride
95% for sodium
78% for potassium
3) most of these substances are technical grade (with other not active substances like chlorides and hydroxides) so that the % active chlorine is lower. This happens in particular with calcium hypochloride, which is usually sold as about 70% active chlorine.
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...
IF the calcium hypochloride were 70% cl active, 7 grams would be equivalent to 7*7/100= 0.49 grams. That is, very close to 0.5%!!!