Re: Bleach-development with gum recipe
Marek or John, You are chemists, correct? Well, when I check online here: http://www.reproline.jhu.edu/English/4morerh/4ip/IP_manual/10_Decontamination.pdf 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 time. 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. Chris Assistant Professor of Photography Photography Option Coordinator Montana State University College of Arts and Architecture Department of Media and Theatre Arts, Room 220 P.O. Box 173350 Bozeman, MT 59717-3350 Tel (406) 994 6219 CZAphotography.com |