But the VALUES in those standards are what are reported in the literature and the test for retained hypo gives a colorimetric indication of these values. I referred to these above.
I remember the test being harder to set up than it was to actually perform it.
The NND reagent is a bit hard to make - you have to get the oxalate salt of the NND and then it's dissolved into concentrated sulfuric acid and it takes a bit of time to get the NND into solution.
The borohydride solution is pretty hazardous, and it doesn't last long in solution.
I've got the bottle of sodium borohydride in my basement as the lab I worked at tossed a bunch of old reagents, and I saved the borohydride from the waste stream. I'm sure I rescued the NND reagent, but I have no idea where I put it... :^(
Other than needing to have a spectrophotometer, it's really not a difficult test to do. It would take a few hours for one strip of film from start to finish.
That is why a drop of Silver Nitrate in Acetic Acid works for me. Thanks Kirk for the painful description. All I need is Sodium Borohydride, the Spectrophotometer and a few other odds and ends............ :D
Well now finally after 30 years, do I have a use for the bottle of silvernitrate I rescued when they demolished the old lab, I found that and a bottle of Hydroquinone..... hmm wonder how that would work with Ascorbic acid or maybe coffee?
Greg - would you let us know how long you treated the films in HCA and your agitation routine in the HCA.
I used it for 2 minutes with initial agitation of 30 seconds, then 5 seconds every 30 seconds thereafter as per Kodak's instructions.
Yes HCA is very important!
so is toning
As a follow up to this test, I wanted to see what rate of flow was necessary for each type of tank I use to get a complete change in 5 minutes as per the instructions from Kodak. I am posting them here.
250mL single reel stainless tank- .2 gallons/minute (.75 L/minute)
500mL two reel stainless tank- .2 gallons/minute (.75 L/minute)
1000mL 4 reel stainless tank- .3 gallon/minute (1.14 L/minute)
500mL generic plastic tank- .3 gallon/minute (1.14 L/minute)
Jobo 1520 2 reel tank- .3 gallon/minute (1.14 L/minute)
Though the volumes are similar for the plastic tank and medium SS tank, the designs of the plastic require a stronger flow to achieve the necessary change of water. The single reel tank actually needed less than stated here, but my meter will not measure less than that.
I have been in between sort of a change from flowing water to standing water (as I have sometimes problems with water quality).
During that, I have monitored washing quality using HT-2 and to my very big surprise, there's no stain in the (sheet) film after only one or two water changes (15 liters per change).
After a fixing, I use a short rinse/wash using same method as with developing/fixing - rotation, tray or slosher, then I put the film sheets on the washing water and within 5-10 minute, I take the films off, change the water and put them back.
So far, after negatives have been on the second water bath for about 20 minutes, there's no visible stain left by HT-2.
To all my knowledge, I would have guessed that at least five or more water changes would be required for that. Perhaps it's the amount of water that makes difference?
So far, I do couple of water changes more just to be sure... But that finding is quite interesting to me.