Leslie test kit aging rate. Interesting.

[morzh]

As I wrote in another thread I tested the two Leslie blue box test kits side by side, one is freshley bought and one is 10 years old (2005). The only different reading was FC, and I suspected the #2 chemical. So tonight I tested it using #1 from the old kit and #2 from the new and the reading came out exactly the same.
So, in 10 years the only chemical that aged sems to be #2.

Again, cannot claim anything, if anyone is interested how it was kept, it was kept in my garage where it is never really hot. Closed.

Make of it what you will.

 

[Divin Dave]

Hi morzh.
I dont know anything about the Leslies blue test kit, or the regents.

I do know however that in the taylor kit and TF100, the only regents which go bad, are the dyes, for testing TA and CH.
That typically is a 18 month period.

 

[morzh]

Yes, the dye. I think #2 is DPD which is what forms the magenta color.

 

[chem geek]

Generally speaking, it is the organic dyes that are the most sensitive. The FAS reagent is also sensitive especially to heat and sunlight. The acids and bases will last an extremely long time. The other ingredients are intermediate. See this post. The "3 years or more" is being very conservative since those compounds don't degrade. DPD is the most sensitive, though it lasts longer in powder form than as a liquid (so exposure to moisture degrades it).

 

[morzh]

I think it is from similar group of chemical (as it is paraphenylenediamine) as the old color developing reagent, T32, ethyl-oxy-ethyl-paraphenylene-diamine-sulphate, or the older one, di-ethyl-paraphenylene-diamine-sulphate, and they also did degrade over time, after 3 or so years they would develop but the colors would not be as bright.