Sodium Met - Mythbusting Time

[lonte]

I just set up my liquor to heat on a timer in time for an 0600 dough in. Added my "usual" 1/4tsp of Sodium Met. I do this as I understand Brisbane uses Chloramine to anti-bacterialise the water supply and Sodium Met cleans it out of the water. I also add a pinch to the grain in my mash tun as I understand it will scavenge oxygen and thus reduce the impact of any HSA should it occur.

I add 1/4tsp to my 40L HLT of cold water, stir well, leave uncovered for a few minutes, then cover and leave until morning to use the water.

OK; things I'd like people to comment on:

1) The container I am using is labelled _both_ Sodium Metabisulphate AND Sodium Metabisulphite - which is it more likely to be, and is there a difference?
2) What exactly is the chemical reaction happening between Chloramine and Sodium Met? What (gases) might be given off? What ions/compounds remain in the brew water?
3) Are the quantities and method I am using effective?
4) Campden tablets (which apparently clear Chloramine also) are Potassium Met - would it be better to use those so I don't add extra Sodium to the hot liquor?
5) what of the use in the Mash tun to reduce HSA impact - what's the reaction happening there ?
6) if I top up the HLT from the tap water, is there still Sodium Met that will act on that newly added Chloramine or is it spent and require another addition?

Many thanks for any feedback, I'm happy to be pointed to other references on the web, however I must say my reading to date there has resulted in "Yes", "No" and "Maybe" answers! I read someone's sig on this board the other day "If you ask 2 home brewers a question, you'll get 3 different answers" - I have a feeling this post may result in the same. That's why I'm keen, even if it gets a bit techo, to see the chemical equations spelt out.

Thanks, MM.

 

[bear09]

I just set up my liquor to heat on a timer in time for an 0600 dough in. Added my "usual" 1/4tsp of Sodium Met. I do this as I understand Brisbane uses Chloramine to anti-bacterialise the water supply and Sodium Met cleans it out of the water. I also add a pinch to the grain in my mash tun as I understand it will scavenge oxygen and thus reduce the impact of any HSA should it occur.

I add 1/4tsp to my 40L HLT of cold water, stir well, leave uncovered for a few minutes, then cover and leave until morning to use the water.

OK; things I'd like people to comment on:

1) The container I am using is labelled _both_ Sodium Metabisulphate AND Sodium Metabisulphite - which is it more likely to be, and is there a difference?
2) What exactly is the chemical reaction happening between Chloramine and Sodium Met? What (gases) might be given off? What ions/compounds remain in the brew water?
3) Are the quantities and method I am using effective?
4) Campden tablets (which apparently clear Chloramine also) are Potassium Met - would it be better to use those so I don't add extra Sodium to the hot liquor?
5) what of the use in the Mash tun to reduce HSA impact - what's the reaction happening there ?
6) if I top up the HLT from the tap water, is there still Sodium Met that will act on that newly added Chloramine or is it spent and require another addition?

Many thanks for any feedback, I'm happy to be pointed to other references on the web, however I must say my reading to date there has resulted in "Yes", "No" and "Maybe" answers! I read someone's sig on this board the other day "If you ask 2 home brewers a question, you'll get 3 different answers" - I have a feeling this post may result in the same. That's why I'm keen, even if it gets a bit techo, to see the chemical equations spelt out.

Thanks, MM.

Spew I just found this thread and it is perfect but has no replies. Its been 4 years - anyone??

 

[Punkal]

Nice necro... Sorry i have no answers but would also be interested in hearing the answer/answers...

 

[MHB]

At least no one can complain that you arent using the search function, (thats a good start to my mind).
You might find this article in BYO a helpful starting point.
I think adding the right amount is going to be fairly important, your utility should be able to tell you how much Cl/Cl-Amine they use and from there you can decide how much Sodium Metabisulphite (or Potassium, its the Sulphite part thats important) as it gives free SO2 which is the part that reacts with the Cl.
MHB

 

[ekul]

The reaction between sulfur dioxide and chloramine is:
S02 + NH2Cl + H2O ---> Cl- + SO4(2-) + NH4(+) + 2H(+)

I assume that the chlorine (Cl-) then goes on to react with the (Na)+ from the sodium metabisulfite to form sodium chloride. Maybe the 2H+ would bond with the SO4(2-) to form sulfuric acid? Not sure what that ammonia would do, maybe bond with the Na+ as well?

This is all just a guess though.

 

[vykuza]

You might find this article in BYO a helpful starting point.
I think adding the right amount is going to be fairly important,

MHB - great answer to a great question (and left unanswered for so long!) too bad that BYO article is absolutely useless. He gives the "how much to use" answer in ounce measurements of campden tablets per 20gal? Seriously?! How much potassium metabisulfite is in a campden tablet? Is it consistent across brands? Do they come in different strengths? According to this you need 7 grams of campden tablets per 40L. Does that sound right to anyone?! I've usually seen uses of 1/2 a tablet for a 23L batch.

One of the first image search hits shows a packet of campden tablets for sale from Midwest Brewing Supplies as having 50 tablets to the ounce. Midwest Link



Edit: I wish to clarify I'm not having a go at you MHB - but whoever wrote that article bloody well phoned it in that day.

 

[MHB]

Funny when I goggled Campden Tablet it came up with Wikipedia as the first link, which gives a fairly concise definition of what a Campden tablet is, weighs and donates to a solution.
MHB

 

[vykuza]

And the Wikipedia article says use one tablet per 20 gal of water. BYO says 1/2 ounce of tablets per 20gal. Considering a tablet is around 0.015 ounces (0.44g according to wikipedia), there's quite a disparity there.

In easy to use terms, a 1/2-ounce Campden tablet can be used to dechlorinate 20 gallons of water.

Given the benefit of the doubt we can assume the quote from BYO is meant to read 1/2 a tablet rather than 1/2 an ounce - then it's still half the dosage recommended in the wikipedia article. Keep in mind the BYO article states that their dosage is 2-3 times the effective dose.


So is it 1/2 a tablet (assumed), 1 tablet (wikipedia) or 1/2 an ounce of tablets (BYO)?

Anyone with the requisite chemistry skills care to work it out?

 

[np1962]

In this Recipe/Article they say to add 1 Campden Tablet to 20gallons of water to remove chloramine.
Nige

 

[drsmurto]

1) The container I am using is labelled _both_ Sodium Metabisulphate AND Sodium Metabisulphite - which is it more likely to be, and is there a difference?
2) What exactly is the chemical reaction happening between Chloramine and Sodium Met? What (gases) might be given off? What ions/compounds remain in the brew water?
3) Are the quantities and method I am using effective?
4) Campden tablets (which apparently clear Chloramine also) are Potassium Met - would it be better to use those so I don't add extra Sodium to the hot liquor?
5) what of the use in the Mash tun to reduce HSA impact - what's the reaction happening there ?
6) if I top up the HLT from the tap water, is there still Sodium Met that will act on that newly added Chloramine or is it spent and require another addition?

1. No such thing as metabisulphate, its metabisulphite.
2. I suspect that its not SO2 that reacts with chloramine but H2SO3 (sulphurous acid) which forms NH4Cl and H2SO4. Any gas that is given off is SO2. The counter ion of metabisulphite (K or Na) will remain.
3. You cant accurately measure a solid using a volume measurement. Teaspoons do not equate to weight directly as you need to take into account the density of the solid. So i have no idea what mass of metabisulphite you are adding. Given you are using it to react with chloramine then the amount of chloramine in the water would be helpful. It also reacts with chlorine but not chloride.
4. Yes but again, how much potassium metabisulphite is in a campden tablet and how much if it is filler. I'd personally use the potassium salt rather than sodium but then i dont add sodium to my brew water.
5. Using it the mash tun is a different beast as this time its the SO2 that is doing the work. SO2 is a reducing agent (anti-oxidant if you want to use media speak) and will react with O2 to form sulphate. This is the basis of its use in the wine industry.
6. Depends on how much you added and how much chloramine was there in the first place.