Two random chem questions for Randy

[reefiniteasy]

First, why does auto top off tubing that’s sitting in the reservoir go from clear to solid white over time, as pictured below?

Second question. I use Fritz glass cleaner. They label the bottles with a lot number and a use by date. Any idea what can change with a glass cleaner that would require it to be used by a certain date?

 

[Randy Holmes-Farley Verified Community Expert]

Second one sounds like an overzelous quality control idea. I'd ignore the date.

Tubing, and plastic in general, can be clear if there are no minerals in it that absorb or scatter light (carbon black for black or grey, titanium dioxide for white, etc.) and if the polymers themselves have not formed into crystallites that can scatter light.

My expectation with tubing that is exposed to fluids, especially organic ones like for organic carbon dosing, is that small molecule organics such as plasticizers have leached out into the water, leaving behind the polymer chains that can more readily come together into crystals that can scatter light.

I have seen that effect myself with tubing that sits in vinegar for vinegar dosing. It gets stiff as well as opaque, but otherwise is not, IMO, a concern (except perhaps for the leached plasticizers).

 

[reefiniteasy]

Second one sounds like an overzelous quality control idea. I'd ignore the date.

Tubing, and plastic in general, can be clear if there are no minerals in it that absorb or scatter light (carbon black for black or grey, titanium dioxide for white, etc.) and if the polymers themselves have not formed into crystallites that can scatter light.

My expectation with tubing that is exposed to fluids, especially organic ones like for organic carbon dosing, is that small molecule organics such as plasticizers have leached out into the water, leaving behind the polymer chains that can more readily come together into crystals that can scatter light.

I have seen that effect myself with tubing that sits in vinegar for vinegar dosing. It gets stiff as well as opaque, but otherwise is not, IMO, a concern (except perhaps for the leached plasticizers).

So I guess it would be a good thing to replace the tubing and rinse out the reservoir from time to time in case it leached anything. Thanks for your thoughts Randy. Merry Christmas!