Calgon™/Sodium hexametaphosphate

Discussion in 'B&W: Film, Paper, Chemistry' started by analogfotog, Mar 3, 2008.

  1. analogfotog

    analogfotog Member

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    I wanted to buy a box of Calgon™/Sodium hexametaphosphate, as mixing my developers, et cetera, is a bit of a problem, as our water is very hard. I have problems with a yucky sludge in my D-23, and whenever I mix hypo clearing agent, not all of the sodium sulfite will stay in solution. The box of Calgon™ I saw in our local supermarket had nothing on the side panel about containing sodium hexametaphosphate. Instead, it said, "...contains sodium sesquicarbonate and sodium tripolyphosphate..."

    Okay, I am obviously not a chemist; can anybody give me some information on this product? First, is it suitable for photographic use? Is it a viable substitute for sodium hexametaphosphate? Or is it just another way of referring to sodium hexametaphosphate? Is there another chemical which could be used, and will not cause the pH of my chemistry, especially my beloved D-23, to get tossed on its ear?

    Please, don't bother posting to advise me to get a water softener; that is not an option.
     
  2. Ian Grant

    Ian Grant Subscriber

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    Why not buy a cheap water filter instead, there's no point in adding extra chemicals when you don't need to. This will give you better water for rinsing the films too.

    Ian
     
  3. Wishy

    Wishy Member

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    Why not just use distilled water instead? I don't think adding more chemicals will do the development process any good.
     
  4. Ian Grant

    Ian Grant Subscriber

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    Distilled water is relatively expensive, a small Britax type water filter produces very cheap use-able water.

    Ian
     
  5. Mike Wilde

    Mike Wilde Member

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    Canadian Calgon experience

    I live in a place where there is relatively soft water in the municipal supply.

    I found in a 'junk week' that someone had moved to town and then thrown out their reverse osmosis unit from when they had previously lived. It was crusted with iron and lime on the inlet filter, so it definitely did its job at the previous location.

    I rehabbed it , and have never been happier. Now I no longer have the need to lug distilled jugs home in the winter from the grocery store.

    when the water is of unknown qualtity I have used calgon, at a rate of 1g/l when processing E-6 away from home. (it was about 1/2 tsp as I recall).

    I have taken e-6 concentrates in the camper when off on car camping trips.

    After filtering and leaving lake water to settle, I boiled it on a camp stove, to drive off dissoved oxygen, then mixed the chems when the water cooled, after I had dissolved the calgon to keep anmy dissoved items in suspension.

    To temper the whole affair I would immerse all the bottles and tank (loaded in a changing bag) in a large wash tub that held lake water and heated on the camp stove water, to bring the whole affair to 100F. Timing was by way of wrist watch. Drying was by way of stove alcohol mixed in 20% with the final rinse - the film was dry in under 5 minutes, inside a camper with only me standing very still for that period of time.
     
  6. john_s

    john_s Subscriber

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    I think I read somewhere that either Calgon is a different product in different countries or that its formulation had changed. Sorry I can't remember where I read it.

    Maybe a chemist could suggest an alternative chemical. Would EDTA-tetrasodium salt do it?
     
  7. Photo Engineer

    Photo Engineer Subscriber

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    Calgon is now no longer Sodium Hexametaphosphate.

    Substitute 10 g/l of Disodium EDTA. You may have to adjust the pH of the final solution.

    PE
     
  8. Tom Hoskinson

    Tom Hoskinson Member

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    I'm an engineer, not a chemist, but according to the chemistry literature, Yes:

    EDTA refers to the chelating agent with the formula (HO2CCH2)

    Sodium Hexametaphosphate is used as a sequestering agent. It is used in the industry of soap, detergents, water treatment, metal finishing and plating, pulp and paper manufacture, synthesis of polymers, photographic products, textiles, scale removal and agriculture. sodium hexametaphosphate was the sequestrant in the original Calgon product. Phosphates have negative environmental impacts.

    sodium tripolyphosphate is a sequestrant

    disodium citrate is a sequestrant listed in a current Calgon MSDS

    Triethanolamine and Diethanolamine are sequestrants (Fe and Ca).
     
  9. Photo Engineer

    Photo Engineer Subscriber

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    TEA and DEA are not very good sequestrants for hard water, and change the pH and buffer capacity.

    PE
     
  10. Tom Hoskinson

    Tom Hoskinson Member

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    Yes, TEA and DEA are best at gettering water and oxygen
     
  11. Photo Engineer

    Photo Engineer Subscriber

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    Tom;

    Both DEA and TEA are rather inert to oxygen chemically. They are strongly alkaline and very mildly chelating. TEA is used as a base in developers.

    DEA is a mild silver halide solvent.

    PE
     
  12. jimgalli

    jimgalli Subscriber

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    You can do searches for Sodium Hexametaphosphate and buy it in a lifetime supply on Ebay. 1 lb. is $8 3 lb. is $13 10 lb. is $27. I have to use it out in the desert where I live or I get calcite bits on my negs after they dry.
     
  13. Tom Hoskinson

    Tom Hoskinson Member

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    You are right on all counts, PE.

    I goofed, sorry!
     
  14. Photo Engineer

    Photo Engineer Subscriber

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    Tom;

    Maybe I should point out that you had reason for your answer. Both TEA and DEA react with air, but not oxygen (readily). It is the Carbon Dioxide that they react with, gradually forming the carbonate salt.

    This will drag the pH more acidic.

    PE
     
  15. Tom Hoskinson

    Tom Hoskinson Member

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    Thanks very much for the clarification, PE
     
  16. Alan Johnson

    Alan Johnson Subscriber

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    See 'Complex Phosphates' here:
    www.chemistry.co.nz/deterg_inorganic.htm
    It may be tripolyphosphate has sesquicarbonate added to reduce alkalinity. I can see no obvious reason why tripolyphosphate should not work provided it does not affect the pH.
     
  17. gainer

    gainer Subscriber

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    That explains why a working solution of PC-TEA or the like, made with my hard well water and left standing in an open pitcher, will turn cloudy as would a developer like Dektol. I'm assuming that the TEA makes a carbonate out of CO2 from air which it hands over to the Mg and Ca in the well water making limestone as the cloudy stuff. OTH, even a glass of well water standing open should become cloudy. Anyway, it's very good drinking water from 110 feet down. If I ever get a water softener, I shall put a tap between the well and the softener for drink.
     
  18. gainer

    gainer Subscriber

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    110 feet down is still about 800 feet above sea level where I live.
     
  19. Photo Engineer

    Photo Engineer Subscriber

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    Patrick;

    Get a high capacity Reverse Osmosis unit. It will turn out deionized water and concentrate the salts in another output.

    Some will produce many gallons per day.

    I meant to add that my wife and I both grew up in the same area at about the same altitude.

    PE
     
    Last edited by a moderator: Mar 5, 2008
  20. Photo Engineer

    Photo Engineer Subscriber

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    Just a general note.

    Our atmosphere is acidic and oxidizing due to the CO2 and O2 in it. Any alkaline solution left out in the open will react with CO2 and form a salt while decreasing in pH. Any reducing solution left out in the air will oxidize. This goes for the solids as well as the solutions I might add.

    Therefore, developer, which is an alkaline solution of reductants goes bad when exposed to air. The CO2 makes it more acidic and the O2 oxidizes the reducing agents including HQ, Metol, Phenidone, Glycin and etc.

    PE
     
  21. Alan Johnson

    Alan Johnson Subscriber

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    In Europe, Calgon powder now contains zeolite, no mention of phosphate:
    www.rbeuroinfo.com
    To remove hardness from water I add 1 teaspoon of this to a gallon or 5 L tapwater,stir well,allow the resulting suspension (zeolite?) to settle overnight.The mostly clear water now with no calcium hardess is decanted to a container.
    To confirm hardess removed I added potassium carbonate solution,it gave no cloudy calcium carbonate precipitate whereas untreated tap water does give cloudiness.
    IMO this type of Calgon powder should not be used in old formulas calling for Calgon,it would likely form a cloudy suspension.
     
  22. Photo Engineer

    Photo Engineer Subscriber

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    Zeolites can exchange ions in the reverse direction, and thus release the Calcium when the developer is mixed with the zeolite. In a Sodium Carbonate developer this equillibrium could then result in formation of Calcium Carbonate during keeping.

    In addition, the solid zeolite that forms can be abrasive to film or get trapped in the wet swollen emulsion.

    PE