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Old 07-09-2012, 02:07 PM   #1
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Default pH of distilled water

Hi there !

Does pH variation also occur in distilled water by temperature variation ?!

I mean , if distilled water have pH 7 at room temperature and if I add enough lactic acid to reduce it to 6.1 , then can I say that

the pH would be 5.8 at 160 F ?!

Hector

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Old 07-09-2012, 04:41 PM   #2
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The pH of pure water does depend on the temperature. At 25 °C it is 7.00. At 20 °C it is 7.08, at 50 °C it is 6.63. Etc. But that's not really what you are asking. You are asking whether water treated with lactic acid has a pH which will vary with temperature and the answer is again 'yes'. Pure water which has been acidified to pH 6.1 at 70 °F with lactic acid would, theoretically, have a pH of 6.7 at 160 °F. This is because lactic acid becomes a weaker acid with increased temperature unlike water which becomes a stronger acid.

Note that I have carefully used the term 'pure water' instead of distilled water in the preceding paragraph. Distilled water will quickly pick up carbon dioxide from the atmosphere and its pH will, as a consequence drop. As so little lactic acid is required to cause the pH shift of pure water at 20 °C to 6.1 this also tiny amount of dissolved CO2 will have an influence on the observed pH. Without accounting for this calculated pH values are not terribly meaningful. Put another way, the buffering capacity of 'acidified' pure or distilled water is so small that other factors will doubtless override the dependence of the acid (or water's) pK's (a number which determines the strength of an acid and thus the pH of an aqueous solution containing that acid.

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Old 07-09-2012, 06:28 PM   #3
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Quote:
Originally Posted by ajdelange View Post
You are asking whether water treated with lactic acid has a pH which will vary with temperature and the answer is again 'yes'.
Thanks for your reply .

I should explain what I really mean by my question .

I'm an Extract brewer and I also use steeping grains . By the first batches , I used distilled water and by later ones , used bottled spring water .

But Tannin bitterness and Husky aftertaste was detectable by all of the Beers .

As I always steep the grains not longer than 30 minutes and by temps not higher than 70 C , I thought that this problem should be due to the pH .

The pH of the distilled water was 6.5-7.5 at room temperature and that of the spring water is 7.2 .

Therefore , I decided to adjust the pH to a lower level in order to get rid of that husky aftertaste .

What is the best way to do this ( preferably with distilled water ) , so that I can be sure that the pH by the time of steeping is below 6 ?

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Old 07-09-2012, 07:06 PM   #4
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Mix the grain with the steeping water, and THEN cool it and check the pH. I doubt it's above 6, unless you are using very alkaline water, and it's probably closer to 5.5-5.8, depending on the grains you're using.

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Old 07-09-2012, 07:31 PM   #5
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Quote:
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it's probably closer to 5.5-5.8, depending on the grains you're using.
I'm using Crystal malt ( 40 L ) as steeping grains .

As I said , I've had husky aftertaste by my previous batches . So , I think that I should do something with the pH .

I tested these grains before and they don't drop the pH effectively .

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Old 07-09-2012, 09:46 PM   #6
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I have to echo what Yooper said. The distilled water pH of even base malts is below 5.8. A colored malt should have a distilled water pH even lower. If you are steeping crystal malt in distilled water and measuring pH above 6 then suspect your pH meter or buffers.

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Old 07-09-2012, 10:17 PM   #7
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Quote:
Originally Posted by ajdelange View Post
If you are steeping crystal malt in distilled water and measuring pH above 6 then suspect your pH meter or buffers.
There is nothing wrong with my pH meter and buffer solutions .

The Crystal malt I'm using is Home-made . I make them at home by using raw Barley .

Raw Barley --> Green malt --> Stewing --> Roasting in Oven

I had husky aftertaste by my previous batches with both distilled and spring water and it means that the pH was
above 6 by the time of steeping at 70 C .

What should I do to lower the pH below 6 ?

Hector
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Old 07-09-2012, 10:27 PM   #8
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Quote:
Originally Posted by hector View Post
There is nothing wrong with my pH meter and buffer solutions .

...

I had husky aftertaste by my previous batches with both distilled and spring water and it means that the pH was
above 6 by the time of steeping at 70 C .
Did you measure the pH of the grain/water mix with your meter, or are you saying it must be above 6 based only on the taste?
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Old 07-09-2012, 10:38 PM   #9
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Quote:
Originally Posted by Yooper View Post
Mix the grain with the steeping water, and THEN cool it and check the pH. I doubt it's above 6, unless you are using very alkaline water, and it's probably closer to 5.5-5.8, depending on the grains you're using.
Not here in st. Louis. I almost always have to add 0.5 ml to 1.5 ml to get the ph correct.
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Old 07-09-2012, 10:39 PM   #10
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Quote:
Originally Posted by Huff360 View Post
Did you measure the pH of the grain/water mix with your meter, or are you saying it must be above 6 based only on the taste?
As far as I know , there are three factors that affect tannin extraction from the husks :

- Duration of the steeping

- Temperature

- pH

I always steep at 70 C and for 30 minutes . So , the only remaining Cause of this aftertaste is the pH .

That was my Conclusion and I'm going to check the pH by the next batch .

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