ammonium alum as a hardener

[quiver]

Was recently browsing the local drug store and found that they have ammonium alum over the shelf. Is it possible to use this as a hardener as a separate bath to a non hardening fixer? It seems to be suggested that it could from this site http://www.jackspcs.com/chemdesc.htm#AMMONIUM_ALUM but I can't find any information about using it for this purpose. If it can be used as a hardener what would be the recommended mixture for this.

 

[Gerald Koch]

Potassium aluminum sulfate commonly called potash alum or just alum is what is usually called for in hardening fixers. There is no reason why ammonium alum could not be used. It is the aluminum +3 ion which does the hardening. However, chrome alum is a better hardening agent. See Kodak SB-3 in the formulas section.

 

[Tom Hoskinson]

ALUMINUM AMMONIUM SULFATE must be handled with care! This is true of the other forms of Alum as well.

WARNING! HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT.

Here is the JT Baker MSDS for Aluminum Ammonium Sulfate:

http://www.jtbaker.com/msds/englishhtml/a2760.htm

 

[quiver]

ALUMINUM AMMONIUM SULFATE must be handled with care! This is true of the other forms of Alum as well.

WARNING! HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT.

Here is the JT Baker MSDS for Aluminum Ammonium Sulfate:

http://www.jtbaker.com/msds/englishhtml/a2760.htm

Naw, really? Sounds about par for the course with most darkroom chemicals. The MSDS basically says follow good procedure and nothing bad will happen. When mixing prepackaged chemicals or my own I always use PVC gloves dust respirator and goggles. Why be such an alarmist about it. Heck I don't even mix vinegar in my darkroom without using these precautions. The only reason I asked instead of going ahead and doing it was that a) It looked like it should work b) No information about using it for this, and c) Making sure that I wasn't about to do something stupid.

Actually I was wondering what would happen when the aluminum ion was striped. Now that I have taken a closer look at the formula it looks like it would decompose into ammonium sulfate and sulfuric acid. The first looks mostly harmless and the other wouldn't be in sufficient concentration to cause a problem. Correct me if I'm wrong.

 

[Gerald Koch]

The alums (sodium, potassium, and ammonium) are not particularly dangerous. Alum has been used in the past to treat mouth and skin sores.

 

[Tom Hoskinson]

Naw, really? Sounds about par for the course with most darkroom chemicals. The MSDS basically says follow good procedure and nothing bad will happen. When mixing prepackaged chemicals or my own I always use PVC gloves dust respirator and goggles. Why be such an alarmist about it. Heck I don't even mix vinegar in my darkroom without using these precautions. The only reason I asked instead of going ahead and doing it was that a) It looked like it should work b) No information about using it for this, and c) Making sure that I wasn't about to do something stupid.

Actually I was wondering what would happen when the aluminum ion was striped. Now that I have taken a closer look at the formula it looks like it would decompose into ammonium sulfate and sulfuric acid. The first looks mostly harmless and the other wouldn't be in sufficient concentration to cause a problem. Correct me if I'm wrong.

Yes, sulphuric acid is one of the potentially hazardous products - Chemical burns of mucous membranes are a very real risk - and one death from Alum ingestion has been reported.

In addition, chemical sensitivity reactions and allergic reactions are a risk. People with a history of asthma risk triggering an asthma attack.

 

[Gerald Koch]

The alums are mixed salts. One is always aluminum sulfate and the other is either sodium, potassium, or ammonium sulfate. As a chemist I can say they are perfectly safe to work with. They will not form sulfuric acid under normal conditions.

 

[quiver]

Yes, sulphuric acid is one of the potentially hazardous products - Chemical burns of mucous membranes are a very real risk - and one death from Alum ingestion has been reported.

In addition, chemical sensitivity reactions and allergic reactions are a risk. People with a history of asthma risk triggering an asthma attack.

Try not to take that one death out of context. That particular person had to eat 30 grams of the stuff to get that particular darwinistic result. I would also imagine that ventilation would help a great deal. So no biggie.

 

[Tom Hoskinson]

The alums are mixed salts. One is always aluminum sulfate and the other is either sodium, potassium, or ammonium sulfate. As a chemist I can say they are perfectly safe to work with. They will not form sulfuric acid under normal conditions.

Gerald, I question your "perfectly safe" statement. Based on the MSDS, working with the various alums should be safe enough if you wear a proper respirator or work under a properly operating chemical hood.

However, if you breathe alum dust particles, the sulfates in the alum can hydrolyze in the water that is normally present in your respiratory tract to form small amounts of sulfuric acid. The resulting burns and irritation can trigger an asthma attack. As an asthmatic, I can tell you that you really don't want to risk that!

 

[Gerald Koch]

You must consider that the MSDS's must cover all users of a certain chemical whether they are dealing with one pound or hundreds of pounds. The caution about alum dust is for commercial users where there are sufficient quantities to raise a significant amount into the air. For the average photographer dealing with perhaps a pound of alum there is no real danger in raising dust.

A solution of 100 g/l of alum has a pH of 3.3, orange juice has a pH of 2.8 and is therefore more acidic. Orange juice certainly doesn't cause burns. As I have said before the alums are not going to generate sulfuric acid. It is not possible unless you heat them to temperatures that would incinerate you first.

I suppose that anything that can cause irritation could also cause problems with sensitive individuals. However I think that you are confusing sulfAtes with sulfItes. Sulfites are well known to cause asthmatic attacks and are found in wine and various foods as a preservative.

If you personally are more comfortable avoiding alums or wearing a respirator then by all means do so.