Saturday, May 19, 2012

Another way to produce a fixer

This time let us use ammonia as fixer. Normally, ammonia is available at your drugstore. If you have a ventilated place where the fumes don't borrow you, just use it as normal fixer, it takes very short time to act and gives a good transparency.

But, if you have problems to purchase Ammonia, a water solution of NH3, let us use Ammonium Sulfate that is sold as fertilizer in all agriculture drugstore and the equation:

2NaOH + (NH4)2SO4 ---> Na2SO4 + 2NH3 + 2H2O

You will end with a mixture of Sodium sulfate and Ammonia. If you search the properties of Sodium Sulfate at Wikipedia, you will find this curve:

Solubility of Sodium Sulfate in water
This curves means that at low temperature the Sodium Sulfate will crystallize or precipitate.


Dissolve 132 g of Ammonium Sulfate in some 250 ml water in a 1 liter beaker. Do the same with 80 g Sodium Hydroxide in a smaller beaker. Pour the solution of Sodium Hydroxide to the solution of Ammonium Sulfate and mix until most of the stoichiometric reaction take place. Let cool and put in your refrigerator. Next morning you will have the bottom full of precipitate, Sodium Sulfate. Just decant to another bottle and yo will have produced Ammonia, perhaps some 10% solution of Ammonia that you can use as fixer in Photography. The smell of this weak solution is tolerable. It works fine, already tested. And it may be reused, I think, until exhaustion.

21st May:

Important notice about ammonia as fixer:

I found this in the Wikipedia:

« silver chloride (AgCl) is soluble in dilute (2M) ammonia solution, silver bromide (AgBr) is only soluble in concentrated ammonia solution, whereas silver iodide (AgI) is insoluble in aqueous ammonia.»

After fixing a piece of film with ammonia I am going to make the sulfide test.


Unknown said...

A little late to the party, but how long does the 10% ammonia solution take to fix the film? I understand ammonia can also dissolve the film if left too long, and wouldn't want to over do it.

Henrique Sousa said...

It is a long time ago that I did it using Fomapan 100 film and Shangai GP3. It took a few minutes, and nothing happened to the film. It was concentrated ammonia and took about 3 minutes to clear, so 6 minutes must be enough to fix.
Better late than never, be welcome!