Home Brew Forums

Home Brew Forums (http://www.homebrewtalk.com/forum.php)
-   Brew Science (http://www.homebrewtalk.com/f128/)
-   -   Conflicting info on amount of Sodium Metabisulfite to de-Chlorinate/de-Chloraminate (http://www.homebrewtalk.com/f128/conflicting-info-amount-sodium-metabisulfite-de-chlorinate-de-chloraminate-163230/)

hafmpty 02-16-2010 12:25 AM

Conflicting info on amount of Sodium Metabisulfite to de-Chlorinate/de-Chloraminate
 
So I seem to be finding conflicting testimony on HBT and the Internet (surprise!) on how much SODIUM METABISULFITE powder I should use to treat my strike and sparge water. For the sake of simplicity let's say I use 20 gallons of water total.

I've been reading that ONE .5gram Campden Tablet is 1/16tsp of Sodium Metabisulfite and will treat 20 gallons of water.

So why am I reading on here that people use 1/8tsp, 1/4tsp, or even 1/2tsp to treat 10 gallons of water. Based on my numbers at least that's overkill. Or is it? Are my numbers wrong? At most, people should be using like 1/32tsp for treating 10 gallons or 1/16tsp for treating 20 gallons. Is is just not that big of a deal? I'm going to be adding brew salts and I know they have to be pretty exact. Maybe Sodium Metabisulfite isn't the same as that?

I'm trying to figure out how much I should use to treat my water. Thanks!

Saccharomyces 02-16-2010 01:17 PM

Our water has a ludicrous amount of chloramine, and one campden tablet in 20 gallons works like a charm. You are correct that would be about 1/16 of a teaspoon in powder form. It doesn't hurt to add too much though since it will just boil off.

Since so little is almost impossible to measure, I crush up one tablet and dissolve it in a few cups of water which then gets added to the four buckets of water in equal 1/2 cup portions.

I have also read of folks using vitamin C tablets to dechlorinate water. :p

Bobby_M 02-16-2010 01:36 PM

Quote:

Originally Posted by hafmpty (Post 1885336)
So I seem to be finding conflicting testimony on HBT and the Internet (surprise!) on how much SODIUM METABISULFITE powder I should use to treat my strike and sparge water. For the sake of simplicity let's say I use 20 gallons of water total.

I've been reading that ONE 5.5gram Campden Tablet is 1/16tsp of Sodium Metabisulfite and will treat 20 gallons of water.

So why am I reading on here that people use 1/8tsp, 1/4tsp, or even 1/2tsp to treat 10 gallons of water. Based on my numbers at least that's overkill. Or is it? Are my numbers wrong? At most, people should be using like 1/32tsp for treating 10 gallons or 1/16tsp for treating 20 gallons. Is is just not that big of a deal? I'm going to be adding brew salts and I know they have to be pretty exact. Maybe Sodium Metabisulfite isn't the same as that?

I'm trying to figure out how much I should use to treat my water. Thanks!

I don't know where you get your campden tabs, but I've never seen a 5.5 gram one. That would look like a horse pill. Mine weigh .5 grams (500mg) each. You're right about 1/16th tsp in powder form is right for 20 gallons. I use a "small pinch" as my exacting measurement.

GilaMinumBeer 02-16-2010 01:39 PM

I use an 1/8th tsp because that is the smallest measuring spoon I have and I don't feel like weighing out a gram of powdered campden.

Yes, I usually get the powdered stuff or I run the tablets through a coffee mill to powder them. Makes dissolving the chemical much easier.

hafmpty 02-16-2010 01:49 PM

Quote:

Originally Posted by Bobby_M (Post 1886150)
I don't know where you get your campden tabs, but I've never seen a 5.5 gram one. That would look like a horse pill. Mine weigh .5 grams (500mg) each. You're right about 1/16th tsp in powder form is right for 20 gallons. I use a "small pinch" as my exacting measurement.

Yeah, sorry. My bad. I should have put .5g. Original thread will be edited to reflect the correct amount.

AiredAle 02-18-2010 05:18 PM

Campden tablets contain sodium metabisulfite, Na2S2O5, they weigh 0.44 g according to wikipedia. According to the chemistry, 1 milligram of chlorine is neutralized by 1.5 mg of bisulfite. Typically municipal water has 3 or less ppm of Cl2 or NH2-Cl (chloramine). So, if one liter of muni water has 3 mg of chlorine, it needs 4.5 mg of bisulfite for chlorine removal. 20 gallons is roughly 80 liters, so 3 X 80 = 240 mg chlorine X 1.5 mg bisulfite = 360 mg bisulfite to neutralize the chlorine in 20 gallons. Since one tablet is 440 mg and probably includes some binder to hold it together, the one tablet per 20 gallons makes sense.

hafmpty 02-18-2010 06:47 PM

Thanks a lot AiredAle. That was very helpful. I'll use those numbers to help me figure out the amounts to put in my water for treatment. It seems like you'd have to try to mess up your water with Campden Tablets. I think I was more concerned with the actual numbers of sulfites going into the water that would be "leftover" than I was anything else. But it seems like the numbers are so minimal it really isn't a problem. Thanks again all.

DeafSmith 11-29-2010 03:48 AM

FYI, I just weighed out 1/8 tsp of potassium metabisulfite powder (packed down) at just about 800 milligrams. So 1/16 tsp would be 400 mg (more or less depending on the accuracy of my measuring spoon) or just almost equivalent to one Campden tablet. I haven't seen any recommendations for using different amounts of K meta vs. Na meta, so I would assume that 1/16 tsp of either is about right for 20 gallons of water.

ajdelange 11-29-2010 12:23 PM

When I came up with the 1 tablet per 20 (US) gal number originally I assumed:
1. A Campden tablet was made up of 695 mg of potassium metabite (because the Campden tablets I had at the time I wrote the article weighed 695 mg and were made of potassium metabite). There could, I suppose, also have been some binder in there.
2. The water being treated contained 3 mg equivalent free chlorine - all as chloramine. 3 is the highest concentration allowed by regulation.

WRT 1 above - Campden tablets can be made of sodium metabite in which case (1) 695 mg tablet would treat more than 20 US gal. One mg chloramine (as Cl) requires 3.127 mg potassium metabite but only 2.674 mg sodium metabite (because sodium is lighter than potassium). The ratio is 1.169 thus you can use 17% less of the sodium salt. Campden tablets may weigh more or less than 695 mg depending on whose you buy.

WRT 2 above -Obviously, if you know that the available chlorine level is less than 3 mg/L you can use less metabite. Furthermore, it takes about twice as much metabite to reduce chloramine as it does chlorine so if you know that part of the available chlorine is chlorine you can use less.

In other words, the 695 mg/20 gal number is designed to protect you against the worst case and is more than is needed in any other case. The good news is that the products of reacted and unreacted metabite (with the exception of the cation) are beneficial to beer in various ways so over dosing is not a problem. OTOH you can use the incremental approach. Crush a Campden tablet with a spoon and add pinches at a time until the chorine odor is gone. When it is, so is the chloramine.

[Edit] The comment about excepting the cation does not mean that they are detrimental. Neither sodium nor potassium in the amount found in a Campden tablet could be considered harmful.

DeafSmith 11-29-2010 03:07 PM

Quote:

Originally Posted by ajdelange (Post 2437968)
When I came up with the 1 tablet per 20 (US) gal number originally I assumed:
1. A Campden tablet was made up of 695 mg of potassium metabite (because the Campden tablets I had at the time I wrote the article weighed 695 mg and were made of potassium metabite). There could, I suppose, also have been some binder in there.
2. The water being treated contained 3 mg equivalent free chlorine - all as chloramine. 3 is the highest concentration allowed by regulation.

WRT 1 above - Campden tablets can be made of sodium metabite in which case (1) 695 mg tablet would treat more than 20 US gal. One mg chloramine (as Cl) requires 3.127 mg potassium metabite but only 2.674 mg sodium metabite (because sodium is lighter than potassium). The ratio is 1.169 thus you can use 17% less of the sodium salt. Campden tablets may weigh more or less than 695 mg depending on whose you buy.

WRT 2 above -Obviously, if you know that the available chlorine level is less than 3 mg/L you can use less metabite. Furthermore, it takes about twice as much metabite to reduce chloramine as it does chlorine so if you know that part of the available chlorine is chlorine you can use less.

In other words, the 695 mg/20 gal number is designed to protect you against the worst case and is more than is needed in any other case. The good news is that the products of reacted and unreacted metabite (with the exception of the cation) are beneficial to beer in various ways so over dosing is not a problem. OTOH you can use the incremental approach. Crush a Campden tablet with a spoon and add pinches at a time until the chorine odor is gone. When it is, so is the chloramine.

[Edit] The comment about excepting the cation does not mean that they are detrimental. Neither sodium nor potassium in the amount found in a Campden tablet could be considered harmful.

So if I'm doing this correctly, for K meta I can multiply 3.127 mg by 3 mg of Cl per liter to get 9.38 mg K meta per liter needed to neutralize 3 mg Cl per liter and then multiply 9.38 by 76 liters per 20 gallons to get 713 mg K meta needed for 20 gallons as the maximum needed? So it might be advisable to use 1/8 tsp (about 800 mg) of the K meta powder per 20 gallons water in order to be certain of neutralizing all the chloramine?


All times are GMT. The time now is 11:43 PM.

Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.