TFTest kit gurus... How do I tell the old from new bottles

[Wntrequinx]

Sooo I might have assumed that the TFTest kit reagent bottles would have some kind of dates on them and took out my new set and the one I was replacing at the same time. I mostly kept them apart until I may have accidentally knocked one out of the bag onto others which fell over and now I don't know which bottle of R0009 reagent is the new one and which is the old one. I had only used a little last year, after my old bottle expired in June - so they are filled about the same.

Any hints as to how I can them apart?

One of them has nothing on the bottom, but the other has an 8, but both R0008 bottle have numbers on the bottom, so I don't know if it means anything. *Sigh*

Also, I is there a *reason* these don't have any best by or packed on dates?

 

[PoolStored]

Put them on a gram scale. The older one will likely be lighter, even if a few grams. ???

 

[ajw22]

I write the year with a Sharpie on the bottles when I get new bottles.

 

[Wntrequinx]

(sorry for not responding sooner, I apparently was coming down with COVID the day I openedmy pool so I was out of it for a few days and then recovering/catching up since then).

Good idea with the weighing it on the scale!

I plan to mark the year on them going forward!!

For now I'll just run all the TA tests twice, once with each solution and take the higher if they are different.