What does Hypo Check react to? (i.e., what causes

I found some old Hypo Check tonight. Being out of it otherwise, I wondered if there was a way to see if it still worked. I put out normal chemistry, played with a few prints and tried a drop of Hypo Check in the fixer - no precipitation. So I figured I was smart (G), and directly poured some developer into the fixer...thought that would kill the fixer. Hypo Check still did not react. So I wonder if Hypo Check reacts to fixer exhaustion more than contamination directly from developer.

Anyone know?

Is there a way to check proper function of Hypo Check?

Dennis

It's 5 or 10 (I forgot) % KJ and the iodine reacts with Ag (silver) which accumulates in your fixer.

Hypo-Chek reacts to saturation of the bath to dissolved silver ions. By dumping developer into the fix you are only altering the fixer pH (acidity), not how exhausted the solution is from silver content.

I'm not a chemist but I think Hypo-Chek is a potassium iodide solution and so maybe the cloud is reacted silver iodide???

Dennis, Hans and Joe are correct.. I was the technical rep for Edwal (manufacturer of hypo check) from 1995-2001. Fixer (sodium or ammonium thiosulfate) removes unreduced silver salts (called silver halide), i.e., parts of the emulsion that were not sufficiently exposed to light, from film and paper. These silver ions build up in the fixer solution.
Hypo check is a potassium iodide solution that when in the presence of a certain level of silver saturation will create a precipitate. There is a fair amount of latitude however. Even when you see a precipitate your fixer is only 50% exhausted. Bear in mind that hypo check does indeed go bad after awhile.

Get a bottle of Hypo Check Check...

Duane -

How does one know when the HypoCheck has gone bad?

I suppose one could keep a small bottle of definitely exhausted fixer and label it "hypo check check". Every now and then just "test" this fixer with hypo check - if you still get the precipitate but dont with fresh mixed fixer, then the hypo check should still be good.

Ron Gratz

then you will need something to make sure your hypo check check hasn't gone bad.

Could it be called "hypo check check check"?

Louis - I believe hypo check has a 5 year shelf life. There should be a date of manufacture on the label.