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Thread: Xtol Oxidation

  1. #1

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    Xtol Oxidation

    While Xtol keeps for a long time in full bottles, it oxidizes in part full bottles. When a bottle is only 10% full the ratio of the volume of air to the volume of developer is over 80 times that when the bottle is 90% full, so the oxidation can go ever faster as the level in the bottle falls.
    I ran some tests on ingredients of Xtol. 2 lots of 12g/L sodium ascorbate without and with addition of 20 g/L sodium sulfite were exposed to the air and the color change noted (see attachments).
    After 37 days the ascorbate alone had oxidized to an orange color, possibly dehydroascorbate as dehydroascorbic acid is reported to be orange. The ascorbate plus sulfite solution showed much less color change.At 130 days the colors had darkened.I cold not get rid of the orange color by adding sodium sulphite.
    I am inclined to favour this explanation for these color changes:
    In presence of sodium sulfite the ascorbate does not oxidize to the orange compound, probably dehydroascorbate, but to a relatively colorless substance which may be an ascorbate-sulfite compound.
    So it is the sodium sulfite which in some cases leads to the oxidative failure of Xtol with minimal color change.
    Thanks for comment.
    Attached Thumbnails Attached Thumbnails Ascorbate vs Ascorbate+Sulfite.jpg   130 days.jpg  

  2. #2

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    Interesting test, Alan.

    A naive question if I may (I know some stuff but I'm not a chemist so bear with me), from an oxidation/stability perspective, is there any difference between Sodium Ascorbate and Sodium Isoascorbate (which is the ingredient in XTOL)?

    Also, while slightly off topic, I wanted to add something related to XTOL oxidation. One of the things people complain about is that they can't tell if XTOL is failing by observing a colour change. However has anyone noticed an odour when it goes bad? I'm asking because I think I have. This was not XTOL which I had mixed and stored, but rather a few batches that had an odour as soon as I mixed them. Normally I don't notice XTOL having an odour of any significance. But around two years ago I received a mail order of 5 or 6 packets (the large ones). Based on the stamped expiry dates they should have been fine, but each time I mixed one of those packages there was an odour. Unfortunately I can't remember with 100% certainty whether the smell was present after dissolving part A or if it came about after adding part B, but I'm reasonably sure the odour was there when part A went into solution, and didn't go away after adding part B. The colours were normal (slight "tawny" colour after mixing part A, which went away after adding part B). And sure enough, while it wasn't "dead", these batches were consistently weaker than normal, requiring longer developing times. I only had that problem with those particular batches. Never had it happen before or since. But I still remember that strange odour. Is an odour perhaps something people could check for before potentially using oxidized XTOL, rather than looking for a colour change?

  3. #3

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    Michael,
    Ascorbate=L-ascorbate is a mirror image of isoascorbate=D-araboascorbate=erythorbate.
    AFAIK the photographic properties of the two are the same as they do not have any reactions in this case where the mirror image type has any effect.

  4. #4
    sun of sand's Avatar
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    Couple weeks ago I used Xtol that I had mixed november 9 2007 and bottled into large 40oz beer bottles
    kept in basement on the concrete at about 43-50 degrees

    Well, the bottle I used was half full and has been used on/off since being mixed


    Worked fine. Negs were done at 9 minutes. I just guessed 9. assorted 35mm film had been shot years earlier so "overdeveloped" it
    3 rolls large paterson tank
    1:1

    Mix it with distilled water
    dont whip in air while mixing maybe
    I use wooden forks
    keep moderately cold
    seal with saran wrap and screw caps

    I've never had failure.

  5. #5

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    Sodium iso-ascorbate which is often called sodium erythorbate is slightly more active as a developing agent.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  6. #6
    Rudeofus's Avatar
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    sun of sand, the difference in stability can be easily explained by the difference in tap water across the globe. People from Australia report, that their Xtol goes bad within days, while yours evidently lasts forever. The key issue seems to be Iron content of tap water. While Xtol uses a powerful sequestering agent (DTPA) to control the Fenton reaction, more Iron still means more remaining effect and less stability.
    Trying to be the best of whatever I am, even if what I am is no good.

  7. #7

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    I aways mix my XTOL in steam distilled water.

  8. #8
    sun of sand's Avatar
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    Quote Originally Posted by Rudeofus View Post
    sun of sand, the difference in stability can be easily explained by the difference in tap water across the globe. People from Australia report, that their Xtol goes bad within days, while yours evidently lasts forever. The key issue seems to be Iron content of tap water. While Xtol uses a powerful sequestering agent (DTPA) to control the Fenton reaction, more Iron still means more remaining effect and less stability.


    My local water
    I have a well
    I don't use tap for anything

    Spring No. 1, analyzed by Profs. Silliman and Norton—
    ..................................Grains.
    ...Sulphuric acid................134.732
    ...Proto-suiphate of iron.........28.623
    ...Sulphate of alumina............21.690
    ...Sulphate of lime...............74.891
    ...Sulphate of magnesia...........35.596
    ...Sulphate of potash..............5.519
    ...Sulphate of soda................6,343
    ...Chloride of sodium..............2.434
    ...Chloride of silica..............4.592
    .....Total grains per gallon.....314.420

    Spring No. 2, analyized by Prof. E. Emmons—
    ..................................Grains.
    ...Sulphate of lime................1.552
    ...Sulphate of magnesia............0.623
    ...Sulphate of iron................4.904
    ...Free sulphuric acid............16.132
    ...Free organic matter.............1.360
    ...Free silica.....................0.230
    .....Total grains in a pint.......24.801

    Spring No. 3, Analyzed by Prof. B. Emmons—
    ..................................Grains.
    ...Free sulphuric acid............12.414
    ...Sulphate of lime................0.736
    ...Sulphate of iron................3.920
    ...Sulphate of magnesia............1.236
    ...Organic matter..................0.100
    ...Silica a........................trace
    .....Total grains in a pint.......18.406

    A writer in the New York Journal of Commerce in July, 1849, gives the following “description of the Alabama Sour Springs:”

    During my stay in Batavia I have visited the Oak Orchard Acid Spring, situated in the town of Alabama, about 14 miles from the village, 18 from Lockport, and 8 miles from Medina. The spring is in Tonawanda Swamp, on a little elevation, on which and in the immediate vicinity eight springs have been discovered, three of which are acid, one sulphur, one magnesia, one iron, and one gas spring sufficient to light 50 gas burners. The principal one is called “sour spring,” from which the celebrated Acid Water is taken, which is carried in great quantities to the Eastern cites, and many boxes sent to the Westenr States. About 25,000 bottles have been sold this past year at 25 cents per bottle. These springs are very highly recommended by Professor Emmons of Albany, Dr. Chilton of New York, and Professor R. Silliman, jr., of Yale College. Dr. Chilton says they contain of:
    ..................................Grains.
    ...Free sulphuric acid.............85.96
    ...Sulphate of lime................39.60
    ...Proto-suiphateof iron...........14.32
    ...Sulphate of alumina..............9.68
    ...Sulphate of magnesia.............8.28
    ...Silica ..........................1.04
    ...Organic extr active matter.......3.38
    .....From one gallon..............160.62

    Prof. Emmons remarks that “the peculiar character of these waters renders them useful in many chronic diseases especially those of the digestive organs and those of weakness and debility.” Dr. James McNaughton of Albany says: “The internal arid external use of these waters I have no doubt will prove valuable in the treatment of several chronic cutaneous diseases.” Dr. Robert Campbell of Pittsfield, Mass.. says: “As medical agents they must be highly beneficial for all chronic diseases of the stomach and bowels.” There are numerous other testimonials from eminent physicians. A good hotel has been erected by Messrs. J. C. Colton of Lockport and Thomas W. Olcott of Albany, which is kept in a very handsome manner by Messrs. Everett & Harrington, two industrious young men, who deserve and have received a very liberal patronage.

  9. #9
    Mainecoonmaniac's Avatar
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    I'm a wino and I use wine box bladders and each batch holds for over a year.
    "Photography, like surfing, is an infinite process, a constantly evolving exploration of life."
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  10. #10
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    Hmm. In my mixing, I have used tap water and not distilled -tried a nearby battery shop - but their distilled water was anything but.
    I am seeing xtol turning deep blue. With usage. Working solution that is. Mixing it 1:3~
    Also, is anyone experiencing that thesolution is getting evaporated with use -that happens even if stored in cool conditions, in shade? (relatively cool -current temps 27-8c in night and 35+c in daytime)

    Sent from Tap-a-talk

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