Potassium Metabisulphite vs. Sodium Metabisulphite: Is There A Difference?

My father spent this past week with my family and I wanted to show him some of the interesting wine making projects we were doing. He has a PhD in bio-chemistry so I thought he'd be intrigued by the process and I wasn't disappointed!

He asked me a very intriguing question: is there a big difference between potassium metabisulphite and sodium metabisulphite as chemically they are quite similar. Why would you use one over the other?

I remember reading somewhere that you wouldn't want to use sodium metabisulphite as a stabilizer in your wine because it adds sodium to it and potentially could could change the taste of your wine. Potassium metabisulphite is therefore the preferred item to use.

I also discussed this with the owner of one of our local wine making supply stores and confirmed that potassium metabisulphite is definitely the way to go and that the only use of sodium metabisulphite in your wine making should be as a sterilizer for your wine making equipment.

This was further confirmed in Alison Crowe's "The Wine Maker's Answer Book" on page 107, where she states:

"Most home winemakers use potassium metabisulphite, available in either powdered or solid (Campden tablets) form, to add sulfur dioxide. There's also a sodium form of sulfite (which isn't recommended for use in wine) as well as a self-dissolving effervescent potassium metabisulphite tablet. I recommend using the powdered form."

> By the way, if you are looking for a good book that covers all of the intricate details about wine making then I highly recommend you purchase Alison Crowe's "The Wine Maker's Answer Book". It is available for purchase via Amazon.com.

Interested in learning more about both sulphites? Here are some good descriptions on Wikipedia:

Potassium metabisulphite - http://en.wikipedia.org/wiki/Potassium_metabisulphite

Sodium metabisulphite - http://en.wikipedia.org/wiki/Sodium_metabisulfite

If you are interested in finding out how to properly calculate the amount of sulphite needed for your wine go to Winemaker Magazine's "Sulphite Calculator", which is available by going to:

http://www.winemakermag.com/sulfitecalculator/index.html

Would be interested to here what your thoughts and experiences are with using these sulphites!