HCA shelf life

[2F/2F]

Is there any reason that HCA stock solution would lose its effectiveness from sitting? If so, how long would it take?

Thank you in advance.

 

[RalphLambrecht]

How does one measure the effectiveness of HCA?

 

[hpulley]

Oxidation. Ilford's washaid says 4 years in a full bottle, 6 months in a half full bottle so pour it into smaller bottles once it starts to get a lot of air in it I guess.

Effectiveness of the wash in general is done by testing for residual fixer. Testing HCA requires that you test plain water wash and HCA wash to see if the HCA wash is sufficient after the fact sheet listed times I guess.

 

[brianmquinn]

Kodak says:

http://www.kodak.com/global/en/professional/support/techPubs/e103cf/e103cf.pdf

 

[Anon Ymous]

Is there any reason that HCA stock solution would lose its effectiveness from sitting? If so, how long would it take?

Thank you in advance.

I assume you're talking about Kodak's HCA. Anyway, as hpulley said, oxidation is the problem. KHCA's main ingredient is sodium sulfite (Na2SO3), which when oxidised becomes sodium sulfate (Na2SO4). The later is used in tropical developers and is worthless as a HCA, perhaps makes things even worse. Well, it definitely makes things worse if you expect to reduce wash times with a dead HCA solution. If I were you, I'd stop using ready made Hypo Clearing Agents and buy sodium sulfite instead. Make a 2% solution for the session and discard it at the end.

 

[RalphLambrecht]

... If I were you, I'd stop using ready made Hypo Clearing Agents and buy sodium sulfite instead. Make a 2% solution for the session and discard it at the end.

Does solid sodium sulfite not oxidize?

 

[Anon Ymous]

Does solid sodium sulfite not oxidize?

AFAIK, anhydrous sodium sulfite is stable, but hydrated forms will sooner or later oxidise. The more water absorbed, the quicker the oxidation reaction. Solutions cannot last long. Thus, buying anhydrous sulfite, keeping it in a well sealed container, and using only what is needed seems to be the best approach.

And since we're talking about sulfite/sulfate, I'd like someone to elaborate on something, perhaps PE can. Doesn't sulfate (the product of sulfite's oxidation) reduce gelatin swelling? If so, doesn't it reduce wash rate, thus making an oxidised HCA solution even worse than doing a "straight" wash for the same amount of time?

 

[hpulley]

What about the ammonium version that Heico PermaWash uses? It works faster. Is that available anhydrous too?

AMMONIUM SULFITE, MONOHYDRATE 10196-04-0 Less than 20%
SODIUM 2-ETHYLHEXYL SULFATE ETHYLHEXYL SULFATE, SODIUM SALT
126-92-1 Less than 5%