shelf life of chemicals

I've never used sorbate, so I don't know. Yeast nutrient should be OK as long as you've kept it dry and it hasn't clumped. Throw away your sodium metabisulfite and buy potassium metabisulfite. That'll keep OK as long as it's sealed in an airtight container, but every time you open the container it'll get a little shot of air and that degrades it over time. If you keep it as a stock solution (dissolved in water) it's even more susceptible to oxidation. Pectic enzyme loses its activity over time, but keeping it refrigerated slows that down. Bentonite lasts forever. The chemicals in your acid testing kit degrade over time.

Tom S

Somewhere on Jack's site he has a fairly extensive discussion of chemicals and how quickly they degrade.

Ray

Why. What is the advantage to the potassium meta?

I said that for two reasons: (1) Whatever you have currently on hand has probably become degraded because of poor storage - either by you or whoever you bought it from. (2) The potassium salt contributes no sodium to your wine. Potassium is a natural component in wine, and any excess can be chilled out when you cold stabilize. That's not the case with sodium, which in excess can make your wine taste - well, salty. This is a pretty fine point, but wineries do not use sodium metabisulfite in their wines.

Tom S

As I understand it, Na Meta is not allowed in commercial wines. Good reason for amateurs not to fool with it either when K meta is available.

Ray