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  #1  
Old 22nd April 2012, 09:29 PM
robinb robinb is offline
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Default Sodium bi sulfite

hi

Im looking to mix some LC1 low contrast developer for use with lith film

http://farahmahbub.com/VirtualMatter/formulasGalore.htm

the formula calls for 10g of Sodium bi sulfite but silverprint don't have this

anybody got any ideas

thanks


robin
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  #2  
Old 22nd April 2012, 10:15 PM
Kat Barnett Kat Barnett is offline
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What about THIS one, Robin? (I found this company when looking for my Sodium Thiosulphate ).

Oops! Sorry I'm getting my -sulphates and my -sulfites mixed up!

Last edited by Kat Barnett; 22nd April 2012 at 10:24 PM.
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  #3  
Old 22nd April 2012, 10:23 PM
Stocky Stocky is offline
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Quote:
Originally Posted by Kat Barnett View Post
What about THIS one, Robin? (I found this company when looking for my Sodium Thiosulphate ).
BisulphAte and bisulphIte are completely different. However you can use sodium metabisulphite which is pretty much equivalent to sodium bisulphite. You can get it where supplies for home beer brewing are sold.

I assume that home brewing is a popular pastime in your country, as it is in mine!
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Old 22nd April 2012, 11:39 PM
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Stoo Batchelor Stoo Batchelor is offline
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Stocky is correct in that you can substitute Sodium Bisulfite weight for weight with Sodium Metabisulfite. You will find it listed at Silverprint's, but it is spelt with a PH, Sodium Metabisulphite.

Stoo
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  #5  
Old 23rd April 2012, 12:24 AM
paulc paulc is offline
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What follows is from http://silvergrain.org/Photo-Tech/ch...misnomers.html, a link that I came across on the unblinkingeye.com web site. The article linked to disappeared a couple of years ago but can still be found on the wayback internet archive. It takes a bit of digging to find.

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Sodium bisulfite, NaHSO3, and sodium metabisulfite, Na2S2O5

Sodium bisulfite and sodium metabisulfite are different chemicals. When metabisulfite is dissolved in water at a reasonably low concentration, one mole of metabisulfite and one mole of water form two moles of bisulfite. Therefore, they are functionally very similar. The difference is the weight they should be substituted at. The difference is small, and is usually nothing to worry about in photographic chemistry. However, in some sensitive developers, this may make sizable difference in pH.

Pure sodium bisulfite is rarely traded for industrial or photographic purposes in dry form, because pure dry form is unstable. However, there is a supplier who sells it in expensive analytical reagent grade in dry form. There are also many suppliers who sell mixture of sodium bisulfite and metabisulfite. The ratio varies across suppliers, but usually about half-half. Sodium bisulfite can be kept in dry form if blended with metabisulfite. Both sodium bisulfite and sodium metabisulfite are most commonly available in anhydrous forms.

Michael Gudzinowicz pointed out that Kodak sells sodium metabisulfite as sodium bisulfite under their label. Kodak's MSDS confirms this. Therefore, when Eastman Kodak Company calls for sodium bisulfite, they mean sodium metabisulfite. If you are buying chemicals from Photographer's Formulary, Johnny Deiure, or other chemical suppliers, I suggest not to bother with higher priced sodium bisulfite, and purchase sodium metabisulfite. If you publish your formula, it is my opinion that correct name for the chemical you employed, sodium metabisulfite or Na2S2O5, is much preferred to avoid further confusion. (at the expense of four more letters)

Richard Knoppow took his effort and found what we think is Kodak researcher's reasoning for this substitution. Crabtree and Mathews (1938) stated as follows: "Ordinary sodium bisulphite has been shown by analysis to consist chiefly of metabisulphite which is converted into bisulphite when dissolved in water. Sodium bisulphite may be substituted weight for weight for potasssium metabisulphite. Either chemical is equally satisfactory but the former is usually preferred since it costs from one-third to one-half the prince of the other and is available on the American market, at least, in a very pure form." (Ch VII, p.117) They further proceeded to say as follows. "The Preservative. -- It is now customary to substitute sodium bisulphite for potassium metabisulphite weight for weight in either developer of fixing bath formulas. According to Harrison and Carrol(1) the stability of commercial sodium bisulphite is a function of its crystalline structure and also of its lack of moisture content. Furthermore, these authors have proved by analysis that there is very little actual sodium hydrogen sulphite present in commercial sodium bisulphite; the major portion of the sample consisting of sodium metabisulphite. Commercially dry sodium bisulphite of satisfactory quality is now obtainable and may be used in mixing formulas calling for either the metabisulphite or the bisulphite. A very interesting discussion of the comparative properties of the sulphites, metabisulphites, and acid sulphites has been published by Wall (2)." (Ch. X, p.215)

Crabtree, J. I. and Mathews, G. E. 1938. Photographic Chemicals and Solutions, Boston: American Photographic Book Publishing Co.

Harrison, J. B. P. and Carrol, M. F. 1925. "The Composition and Evaluation of Commercial Sodium Bisulphite," J. Soc. Chem. Ind., 44, 127.

Wall, E. J. 1927. "Sulphites, Metabisulphites, and Acid Sulphite," American Photography, 16, 127
A few corrections made to spelling errors, but please note the original author(s) use "sulfite" in place of "sulphite" - It is an American thing, so please accept my apologies.
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  #6  
Old 23rd April 2012, 06:53 AM
Dave miller Dave miller is offline
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Sodium Metabisulphite is available from any home wine/beer shop as it is used for sterilisation of equipment and to stop wine fermentation when required.
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  #7  
Old 23rd April 2012, 06:58 AM
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Trevor Crone Trevor Crone is offline
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Robin, as Stoo and Paulc have already pointed out Sodium bisulfite is the same as sodium metabisulphite (correct English spelling).

I get mine from Silverprint as it's also used in solution A in the PMK pyro formula.
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Old 23rd April 2012, 10:51 AM
Lostlabours Lostlabours is offline
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Sodium Bisulphite is not the same as Sodium Metabisulpite they have slighly differing anti-oxidant properties. J.T.Baker sell both for Industrial use and where a stronger preservative or sterilising effect is needed - typically in the food & wine industry - Metabisulphite is used.

The problems is that commercial Sodium Bisulphite is a mixture of Sodium Metabisulphite and Sodium Bisulphite and it's variable.

You can substitute Metabisulphite for Bisulphite with no ill efects but the other way around may not be give enough anti-oxidant effect.

In Europe these chemicals are manufactured differently to the US and we can get good Sodium Metabisulpite whereas in the US Sodium Bisulphite is more common. This is similar to Sodium Carbonate (Anhyd) being the common form here and Sodium Carbonate (monohyrate) in the US.

Ian

Last edited by Lostlabours; 23rd April 2012 at 11:10 AM.
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  #9  
Old 24th April 2012, 07:04 AM
robinb robinb is offline
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thanks for all the information

Sodium Metabisulphite it is

robin
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  #10  
Old 25th April 2012, 05:33 PM
Mark J Mark J is offline
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Default potassium ?

Hello Chaps
Could I lob in an extra question here - topical - as I've been trying to source some sodium metabisulphite , had some sent by Rose Chemicals today, and he's subbed Potassium Metabisulphite . Does anyone know if this is a direct alternative, before I mix up some PMK at the weekend ?
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