Obtaining Cadmium Bromide

[fdonadio]

Hello, all!


I am still planning on trying wet plates. I made my first batch of plain collodion and everything worked out OK. Now, I need to salt that collodion.

Looking on the web, it seems the best compounds for bromo-iodizing collodion (that lasts longer) are cadmium salts. Cadmium iodide is kind of easy to find locally, but cadmium bromide, on the other way, is pretty hard — and very expensive!

I can source hydrobromic acid and metallic cadmium for cheap. Well, the hydrobromic acid is not that cheap (around $50 per liter), but still way cheaper than readymade cadmium bromide. The cadmium costs around $14 a pound and the seller says it's very pure (99.996%), but it's not available as powder or pellets; it only comes in rods around 3/8" (10mm).

I understand cadmium is bad for health and I would need to cut that rod into smaller pieces or find a way to grind it into a power (that would be terrible, I think), but don't know how. Any idea if (and how) it would work? Should I look for cadmium in other forms instead? Or should I just forget about that and buy readymade cadmium bromide?


Cheers,
Flavio

 

[Photo Engineer]

If you must, then buy it ready made. Cadmium and its salts are very insidious in their action on humans. Be very careful.

PE

 

[Herzeleid]

Hydrobromic acid and bromine in elemental form can be as dangerous as water soluble cadmium salts.Working in a fume hood is important with bromine.
If you don't prefer to use potassium salts, insist on cadmium buy them pre-made.
I am making my zinc iodide for collodion, its shelf life is not good as cadmium, but it is very safe to make and cost effective. I buy bromide salts pre-made.

 

[fdonadio]

Thanks, @Photo Engineer and @Herzeleid!

I chose cadmium because that's what most books cite; the Formulary sells that on their collodion kit (the Old Workhorse); and some guys I know here in Brazil tried a lot of stuff and settled on cadmium. They swear by it, but they have to buy from abroad, which gets expensive, burdensome and may be even dangerous.

My idea is to source chemicals locally and even how to obtain the compounds, so I can sell (at a fair price) to fellow photographers, besides using them myself.

Potassium and sodium salts are known for a very short shelf life. I've heard ammonium salts should be good enough. I've read about lithium being as good as cadmium, but it's even more expensive.

Maybe I'll just stick to a mix of ammonium bromide and cadmium iodide but, still, I would like to know if it's safe to cut that cadmium rod into bits with some tool (cutting pliers?) and react the smaller bits with hydrobromic acid. The reaction is very simple and most of the metal — pretty much all of it, I guess — should turn into bromide, with lots of hot hydrogen (and some nasty acid vapors) being released!

Cheers,
Flavio

 

[Photo Engineer]

Flavio, try contacting Mark Osterman at GEM. He is a world authority on this sort of problem and could certainly help you out.

PE

 

[fdonadio]

Flavio, try contacting Mark Osterman at GEM.

Thanks, PE. I'll try to contact him ASAP.

 

[Herzeleid]

Flavio,

Certainly contact Mark Osterman, he might suggest you something different.
I have used his published potassium collodion formula for quite a while, and I still use it from time to time.
Cadmium salts are expensive to obtain around here too, it is imported. But people buy because of the risks involved.
Btw, lithium collodion's shelf life is worse than potassium, and it makes an extremely fragile collodion.

 

[fdonadio]

Btw, lithium collodion's shelf life is worse than potassium, and it makes an extremely fragile collodion.

Good to know, thanks. I don't remember where I got that information about lithium, but I can say it's not popular.

 

[Gerald C Koch]

At one time icebox shelves were plated with cadmium metal. The good old days were also dangerous. An entire family was poisoned when they used a shelf as a grill on their BBQ. I don't remember whether any survived.