Your problem, not mine. I did not in any way say that salt was equivalent to sulfate. I suggested trying the experiment suggested by Anchell & Troop while waiting for the sulfate to arrive. You are so intent on proving me wrong about anything I say that you are making a fool of yourself. The original post was referring to a particular formula and so was I. If anyone is wrong, it is Anchell & Troop, and their sugested experiment did not claim that chloride and sulfate are the same, but that if the chloride is used, the sulfate ought not be necessary.
Originally Posted by Photo Engineer
Just checked with A&T. They suggest using sodium
Originally Posted by disfromage
chloride as substitute for sodium sulFATE; bath
A or/and B for that Microdol effect.
Don't blame me.
BTW, via Google, TD-201 film developer . Interesting
two bath D23 types detailed. Dan
Originally Posted by DarkroomExperimente
You are confusing solvent with restrainer.
A solvent dissolves grain and is used in Microdol and D-76 (Sodium Chloride and Sodium Sulfite respectively).
A restrainer slows down development, lowers fog, lowers contrast and decreases speed. It is usually used to restrain fog.
I am intent on clarifying either the OP or the advice given regarding it, or a possible misprint in A&T. See Dan's post.
Originally Posted by gainer
You cannot and should not use Sodium Chloride to replace Sodium Sulfate or Sodium Bisulfate.
Let us be clear that Sodium Chloride, Sodium Bisulfite and Sodium Sulfite are mild silver halide solvents and are used that way in many film developer formulas.
Let us be clear that mixtures of Sodium Bisulfate and Sodium Sulfate make a buffer solution. One cannot be substituted for the other unless the final pH is known and corrected for by addition of Sulfuric Acid or Sodium Hydroxide.
Whoever suggests otherwise has made a misstatement.
In reference to the OP, your answer was not clear and you appear to have missed (as I did, but as Dan has caught) that there is apparently a misprint in A&T. After all, you did equate Sodium Sulfate with Sodium Chloride in its action in a developer thereby perpetuating, not catching the error.
I postulated an error in the OP, not thinking of there being an error in A&T. It is pretty good in that regard and Bill has an errata section on his web page (or at least he did).
I don't have Anchell and Troop in front of me, but I doubt highly that sulfate and bisulfate form a buffering solution that would even be remotely useful in photography. The pKa for the second ionizable proton in sulfuric acid is 2, which is far too low for any photographic process that I can think of (except dichromate or permanganate bleaching, which is generally not carried out in a buffered solution).
I do remember reading of some other photographic uses of sodium sulfate -- in developers meant for use at high temperatures, IIRC. I don't know what the mechanism of action is.
The issue here seems to be that A&T suggest a couple of different "variants" on the same developer, and some are assuming that these variants are meant to produce the same result or have the same chemical function. From the OP, that isn't clear to me, and so it's probably not useful to speculate further until someone posts the relevant section of A&T here.
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Originally Posted by Jordan
You are entirely correct. The buffer point is too low, but given the popularity of the acidic Amidol developers and other variants, I was not willing to argue based on that point alone. That is why I suggested that the OP might be wrong. It seems that A&T may also have an error.
But, there seemed to me to be also some off chance that this was used in a carbonate or borax developer as a swell supressant which is another thing I considered. It is used in tropical developers to prevent excessive swell as you point out.
Originally Posted by Photo Engineer
First let me state that I am dreadfully sorry that I made that comment about PE's motives. I know that if we were together in the same room, we would not have had some of the interchanges you have seen here. I am old enough to spend a lot of time talking to myself about dumb things I do. "Gainer, you ass, why did you do that?" I used to have interactions with office mates that made witnesses think we were deadly enemies, and then we would take a break, go out to the Coke machine, flip to see who paid, go back into the fray, and eventually solve the problem.
The stated function of the sulfate in the original recipe was in fact to reduce swelling of the emulsion. The chloride is not as effective in that function, but it serves the additional function of silver halide solvent. I would assume that is why A&T suggested that if sodium chloride is added, the sodium sulfate should be left out. The OP simply wanted to know if sulfate and bisulfate were interchangeable, and there was nothing wrong with PE's reply. My comment was in effect, here is a good reason to try the experiment suggested by A&T because ir might take a week or more to get sodium sulfate, but non iodized salt is commonly available at the grocery store, and at least it's food grade, and canning salt IIRC is maybe even better.
Emulsion swelling is a subject of considerable discussion in Mees & James, as I know PE knows quite well, and there is a list of various salts in order of their ability to promote swelling, but no numerical values attached. Sulfate is least likely to promote swelling and chloride is about halfway up the list. There is also the statement that in an alkaline developer, the thing that keeps the alkali from excessively swelling the emulsion is the salt content, meaning salt in the general way, not specifically sodium chloride.
I am not telling PE anything new, as he illustrated in Post #16 above. It seems strange to me that no one has read A&T's rationale for the original formula or that for the suggested revision. It's in Chapter 9 under the subheading D-23 two-bath developers.
See this Thread: http://www.apug.org/forums/forum37/4...perceptol.html
Also see: Modern Photographic Processing, Grant Haist, Vol. 1, 1978, page 379 tells us:
"According to Van Veelen and Peelaers, Sodium Chloride, added in a high concentration to a developing bath of low activity, dissolves silver bromide or idobromide and solution physical development can occur.
Less salt (i.e. less than 30 grams/liter) is said to give more grain but increase film speed."
Last edited by Tom Hoskinson; 12-25-2007 at 12:29 AM. Click to view previous post history.
Everything is analog - even digital :D
Regarding Sodium Sulphate Na2 SO4, I know of two main uses. The main use I have of this chemical photographically, is, as an ingredient in B&W tropical developers.
Itís main purpose is to reduce the swelling of the emulsion, which, when that happens to an extreme, the emulsion will lift off and is poured out with the developer, I have had this happen. The result, is very patchy negatives.
I currently have about half of a 10 kg container of this stuff (technical grade).
The formula that I have used quite extensively when I lived in a very hot part of the country and the cold water temperature was approximately 30 C was this:-
Metol 2 gm
Sodium Sulphite Anhyd 50 gm
Hydroquinone 5 gm
Potassium Carbonate 30 gm
Sodium Sulphate 45 gm
Potassium Bromide 1.5 gm
Water to 1 litre.
Development time is about 2 minutes at 30 C or 2 ľ minutes at 29 C with Plus X film. You cannot use a pre-wet at this temperature and you have to use the developer neat.
That other use I know for this chemical is for medicinal purposes, would you believe?
It is commonly sold under the name of Glauberís Salts! The German chemist Glauber, found that taking this salt mixed in water, had a purging effect and therefore cleared the intestines of unwanted matter.
I can testify that itís cathartic effect is relatively quick, not necessarily painless, but, it works.