Heating sodium bicarbonate to produce sodium carbonate

Discussion in 'Black and White' started by lex_jenkins, Sep 28, 2003.

  1. I'm looking for some definite information on heating sodium bicarbonate (baking soda) to produce sodium carbonate for homebrewed darkroom recipes.
    So far what I've read seems to indicate that the process isn't particularly critical: heat 'til moisture's evaporated; done.
    Info from the following URL seems to corroborate this:
    Does this sound about right? No particular testing necessary to confirm that one does indeed have sodium carbonate and not bicarb?
    Also, can heating be done in the microwave rather than on a stovetop or in a conventional oven? (Fact is, I've already done this - I'd just like some assurance that what I have is in fact sodium carbonate.)
    Thanks, all.
  2. That URL you provided does sound correct. There is a funny anecdote in the <a href="http://unblinkingeye.com/Articles/VitC/vitc.html">Gainer Vitamin C article<a/> where Patrick describes the process:<p>
    "A third method of getting sodium carbonate locally, wherever you may be, is to heat baking soda. The temperature required is quite high. I used a stainless steel saucepan on the stove top. When the baking soda is hot enough, you will see little geysers of steam and carbon dioxide which are fun to watch, but which spray powder around. I convinced my wife that the white coating on the stove was an excellent degreasing agent, but I still had to clean it up"<p>
    Regarding yeild, here is some more from that excellent article:<p>"A pound of baking soda yields 10.6 ounces of anhydrous sodium carbonate, which is equivalent to 12.4 ounces of monohydrated sodium carbonate. One tablespoon of this anhydrous carbonate weighs about 8.8 g"<p>
    Although, it does seem a lot of trouble to go to when you can buy Sodium Carbonate (98 or 99% pure) at a local pool suppliers real cheap. I got 4.5 Kilos (10lbs?) for around 12$NZ (approx 8$US). It's lasted over a year! Product names to look out for are "pH Plus" made by Olin in the States and "pH Increase" here in NZ.
  3. Thanks, Nicholas. I'd forgotten about that Gainer article. Sounds like the microwave will be struggling to get bicarb hot enough. I'll use the stove and watch the show.
  4. Should work just fine, though I wouldn't use the microwave. Only "lossy" materials heat well in the microwave- if it contains water it will heat well. Things like dry chemicals and oil absorb very little power- I tried to heat mineral oil once and it just sat there. Not too good for the microwave either.
  5. Reheating on the stovetop did remove some additional moisture but I didn't get any fun steamers. Apparently the microwave did a fairly good job but couldn't get out that last bit of vapor. As Conrad said it doesn't appear to be too good for the nuker either - it shut itself down and wouldn't restart 'til it had cooled off for awhile.

    Well, I'm gonna go experiment with some under-the-kitchen-sink chemistry, see what develops.

    Sorry. ;>
  6. I'm looking for some definite information on heating sodium bicarbonate (baking soda) to produce sodium carbonate for homebrewed darkroom recipes.
    So far what I've read seems to indicate that the process isn't particularly critical: heat 'til moisture's evaporated; done.

    The URL you gave suggests heating to constant mass, that is until the reaction stops. With stove top heating, I'd be inclined to continue heating for a short time after all visible activity has ceased. And you don't want to get it too hot -- though there's not much danger of doing so on a stovetop, it is possible to calcine carbonates with excessive heat, essentially driving off the remaining carbon dioxide from the carbonate; this is the process used to create quicklime, calcium oxide, which "slakes" in water with release of considerable heat to become calcium hydroxide. Sodium would do the same thing, though it would require higher temperatures and the resulting sodium oxide would be even more prone to draw water out of the air than is quicklime.
    In any case, the microwave isn't the best place to heat items that don't absorb microwaves well; the feedback can damage the klystron tube that produces the power, and require replacement of the oven (since a new tube with installation is likely to cost more than a new nuker).
  7. Thanks, Donald. I suspected as much and heated the bicarb only for a few minutes after all evidence of moisture vapors had ceased.

    The microwave I was experimenting with is pretty beat and needs replacing anyway. Don't wanna do anything dangerous tho'.

    So far I've brewed up a functional - not to say practical - developer from: equal parts Kodak HCA and sodium carbonate; a dash of borax; a dose of vitamin C; and lye. Until I added a few sprinkles of lye nothing happened. For all I know the lye alone would have blackened the scrap paper I'm experimenting with.

    The first thing I've noticed is an overall change in tone on the scrap paper, long expired Ilford MG III. This paper will take an image develop out but the image remains beige and lacking in contrast in either Ilford Multigrade or Alta ZonalPro developers. In this homebrewed developer the paper is nearer to a neutral or cold black.

    Now I'm going to try it in the darkroom on a few test prints. It'll be interesting to see whether something useful can be done with this old paper, if only for experimental and not archival purposes.
  8. As a former industrial chemist I ought to know this but since it's a good twenty years since I had any involvement with chemistry I had to shake my brain-cells up (yes, both of them!) on this one. A microwave certainly wouldn't get the temperature necessary to bring about the decomposition. I would suggest you need to get up to about 350-400 C. The best approach might be some kind of ceramic pot and a gas-torch. Sodium carbonate can be decomposed further but this would need far higher temperatures than could easily be reached in a domestic situation - unless you have a blast-furnace in the corner of the yard.
  9. A second note on microwaves. They are tuned to the frequency of vibration of the hydroxyl radical which occurs in water and some other compounds, e.g. carbohydrates, such as sugar. This is why the jam in the centre of a doughnut gets to scalding temperatures. Liquids with no hydroxyl radicals (e.g. mineral oils) won't heat up.
  10. Here's a scanned negative from my first completely homebrewed batch of developer, including sodium carbonate from "cooked" sodium bicarb. Again, the ingredients were, loosely measured: 1 tsp each Kodak HCA (my only source of sodium sulfite) and sodium carbonate; 1/4 tsp borax; 3 500mg vitamin C tabs; approx. 1/8 tsp sodium hydroxide (Drano, all I had handy - I strained out the undissolved black "pencil lead" cylinders); in 2 cups water. A print from this mixture on Agfa 310 RC had the same tonality as a commercial developer. However it had 1/4-1/2 stop less effective speed and there was diffuse fogging evident on the print, especially at the edges. The print came up almost immediately but I gave it three minutes. The results were encouraging enough to try the brew on film. I pulled 10 already exposed frames from my Olympus XA3 (Tri-X at EI 1600, intended for Diafine). Development: 15 minutes at 73F, 3 inversions every 30 seconds for 5 minutes followed by 1 inversion every 30 seconds for the remainder. A vinegar/water stop bath was used, something I rarely do with film but did in this case because the developer is rather "slimy" feeling. After a few minutes in rapid fixer I peeked and noticed the film had a rather heavy and peculiar tint that was part bluish/purplish (familiar) and orangey which I attributed to the oxidized vitamin C tabs. I gave the film another 15 minutes in the fixer which cleared all but the brownish tint. Washing and Photo-flo as usual. It will be interesting to see the results of this stained emulsion on conventional prints. According to what I've read the effects of pyro staining cannot be adequately conveyed or appreciated by scanning negatives so I won't make any snap judgements here. Some global tweaking was needed to achieve this jpeg interpretation from a rather murky original scan. Some of the interim versions were interesting in a Holga-ish way but I went with a more conventional interpretation of the overall tonality.
  11. Somehow my post on making sodium carbonate from baking soda and lye got into the thread about stand developing. I won't repeat it here.

    HCA probably has hydroquinone in it. Many do not know that hydroquinone with little or no sulfite is a staining developer comparable to catechol. I have never seen vitamin C stain a negative or print, but I have used hydroquinone in place of catechol (pyrocatechin) in Pyrocat-HD developer with nearly the same result as with catechol.
  12. Fascinating. I did not know that, Patrick. Thanks for the tip. You may have helped clear up a couple of quirks I experienced with my homebrew.

    Kodak HCA lists as ingredients (in order): sodium sulfite; sodium metabisulfite; sodium citrate; ethylenediaminetetracetic acid tetrasodium salt. No specific mention of hydroquinone.

    While my book (Manual of Photography, 7th ed.) does not describe any staining properties for hydroquinone, it devotes only a paragraph summary.

    However it does specify that a strong alkali/caustic soda is needed to activate it. That may explain why my homebrew was inactive 'til a sodium hydroxide component (Drano) was added. This seems to corroborate that, if not hydroquinone, at least some superadditivity was going on.

    Hydroquinone is also described as having a risk of fog when used with high speed materials - that may explain the unevenness I saw on both my prints and film developed in this homebrew.

    Finally, while my reference lists this as suitable for low temperature processing, I saw dramatically more activity at higher temperatures. As the soup cooled to room temperature activity dropped significantly and extra time in the developer did not match results obtain from its use at higher temperatures.

    Again, Patrick, thanks always for your research into this area and feedback to this forum.
  13. I made a great booboo. I had forgotten what HCA stood for.

    I think you were right when you said that the NaOH alone would develop the paper. It most likely has a developing agent in the emulsion. I know MGIV does.

    You would get better results on film by adding a little Metol or phenidone. Ascorbic acid by itself is not very good, even with sulfite. It needs the carbonate to work at all because it has an extremely long induction period at lower pH. With a dash of metol, phenidone or p-aminophenol it works at a pH like D-76.

    Sometimes, a brown colored negative is a sign of very fine grain.

    What I said about hydroquinone being a staining developer still goes. I will tell you a little secret that may come out in the March/April issue of Photo Techniques. Hydroquinone and Phenidone are soluble in alcohol at least to the point where 5 grams of hydroquinone and .2 grams of Phenidone will dissolve in 100 ml of propanol. No sulfite is necessary. A 10% solution of NaOH (lye is better than Drano and should be available at supermarkets) is used as accelerator. Use 5 ml of the developer solution and 5 ml of the NaOH solution with 500 ml of water. Develop 400TMax or HP5+ 8 minutes at 70 F.

    What you have then is a sulfite-free equivalent of Pyrocat-HD. If you have catechol, you may use it instead of hydroquinone.
  14. Patrick

    An off topic question:

    In an ascorbic acid/borax developer, to increase pH a bit would it be better to use some sodium carbonate or some sodium hydroxide?

    (Upon reading your article re Vit C devs this was not clear to me).
  15. I followed up Sunday night's test with a slight variation. This time I omitted the vitamin C. Otherwise the formula was pretty much the same.

    It developed a test strip of old MG III paper immediately. I assumed that meant it was okay to proceed with film.

    Natch, I'd forgotten the longtime reports that Ilford MG III was developer incorporated.

    My Tri-X film came out completely blank this go-'round. Not even any film edge markings. Zippo. Clear film base. No tannish stain either.

    I *might* have omitted an ingredient other than vitamin C so I'll repeat the experiment, tho' this time only with a test strip. I'm not going to bother with exposing another roll of film (actually, a very short roll, but nevertheless it took 15 minutes or so). However I was careful to move ingredients from left (indicating not yet added) to right (added).

    Mebbe that was some sooper-dooper vitamin C.
  16. Jorge,

    I would use lye (NaOH). The advantage for me is that I have hard water. When I use borax, the hardness has no effect. With carbonate, I get a precipitate tht takes a long time to settle. Lye and borax do not.

    If you have or have access to a CRC Handbook of Chemistry and Physics, you can find a table of various buffer solutions. Borax alone is about 9.2 no matter what the concentration. The table shows amounts of standard solutions to mix with water to make 100 ml.

    You probably had not read my most recent post yet. A strong solution of sodium carbonate will develop most current RC VC papers because of the incorporated developing agent.

    I forgot to mention that the best place to get alcohol that is as near dry as possible is at an auto parts place in the form as a gasoline drying agent. You can usually find either methanol or propanol. I prefer propanol for use as a preservative because it is not so volatile as methanol, and also not so poisonous. You can also use glycerin that you can get at the drug store. Of course, it is quite viscous. To disslove the hydroquinone and phenidone, you will need to heat it somewhat. Use a hot water bath. You can go as hot as boiling water without problems.

    Sulfie-free hydroquinone developer gives very fine grain.
  17. Thanks, Patrick
  18. Lex, there are some notes about this on Ryuji Suzuki's interesting photo chemistry site:

  19. Patrick,

    In a recent post to this question (and I apologize for going off the topic) you said that glycerin from the drug store could be used to dissolve the phenidone in but it had to be heated in a hot water bath. How much phenidone to how much glycerin? Does the glycerin need to be diluted in anyway before blending in the phenidone? I have been using rubbing alcohol for the phenidone in the VitC developer that I have been using but would like to try it with the glycerin.

  20. KC,

    You can make at least a 1% solution, which is what I use. The bottle I get at the drug store is 4 ounces, close enough to 120 ml, so you could dissolve 1.2 grams of phenidone. It doesn't have to be extremely hot. The viscosity of cold glycerin is about the same as molasses in January or HC110 concentrate. I heat mine in a small microwave for 30 to 60 seconds, or until it is not much more viscous than water. I don't think you should use the plastic bottle for heating, but use something like a Pyrex measuring cup. Let it coll and you can put it back in the original bottle and change the label.

    A better choice than glycerin would be propylene glycol, which you can get at Photographer's Formulary by the pint. It is less viscous and cheaper in the long run. You can also make solutione of hydroquinone, catechol, pyrogallol or ascorbic acid in either glycerin or glycol. They will keep without sulfite, and allow you to play with sulfite-free developers. You will be surprised at the fineness of grain you can get without any halide solvent! Keep an activator solution separately as if for PMK or Pyrocat-HD.
  21. Patrick

    Both phenidone and ascorbic acid solves well in alcohol.

    Any idea about the keeping properties of such mix (assuming alcohol is very pure - over 95%)?

  22. Jorge,

    Not yet, but I'm working on it. I have a solution of ascorbic acid and phenidone in propylene glycol that is 2 months old and shows no loss of activity. I heated it to 250 F when I dissolved it. I would think anything that was going to happen at room temperature would have happened then. I have also made alcohol solutions using isopropyl alcohol from the auto parts store in the form of gas drying stuff. It is about 99% pure and much cheaper than anywhere else.

    If you want to try it out, you can get propylene glycol automobile antifreeze (Sierra is one brand) or if you're not too worried about dogs or children getting into it, you can use the standard ethylene glycol antifreeze. The stuff that makes it green doesn't seem to have any effect on the developer activity.

    It would be nice to have a microwave with a temperature sensor, as some do. None of the glycols will boil at 250 F, but water will be driven off. Ascorbic acid will dissolve enough to make a 10% solution, and the amount of phenidone needed to activate 250 ml of this solution is only 0.25 grams, or about 1/8 teaspoon.
  23. Thanks, Patrick.

    I will give propylene glycol a try.

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