Author Topic: Phosphortic Acid question  (Read 1905 times)

Offline mr_beer

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Phosphortic Acid question
« on: July 04, 2020, 03:41:57 PM »
I purchased a quart of 85% Phosphoric Acid by mistake.  I should have purchased 10% instead.

At the levels that Beersmith recommends for acid addition during the mash step for my size batches (5 to 7 gallon) with my well water the amount required is .04 teaspoon ? obviously impossible to measure.

So I want to dilute the 85% down to a more standard solution of 10% with distilled water that would be easier to handle and measure.

Chemistry and dilution formulas are a long time in my past.  So I thought I would solicit a view on the dilution process.

A strict percentage calculation would yield a .118 conversion factor -- --
   5 ounces of 85% PA to 42 ounces of distilled water

And then I got confused ? are there contributing ions and other factors to this dilution? 

Any help would be appreciated.

Offline RiverBrewer

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Re: Phosphortic Acid question
« Reply #1 on: July 04, 2020, 04:58:42 PM »
I use 85% in every batch and using Bru'n Water calculator for years, bit complicated, but learnable but excellent. There you can enter your acid strengths! Water calculators take a lot of hands on experience to be proficient with. The BeerSmith water calculator has made great strides since it inception. I don't use it, I just check out occasionally. It is a very complicated water analysis process to simplify! The upgrade and improvements I have received strive for better accuracy, a newer look, but simplifying use is very slight. I uses a 10 ml in 1/10 glass pipet to add the acid to brewing water. You can usually find new & used ones on ebay. You would just have to convert  teaspoons to mL and check out what is in the options menu for volume.
« Last Edit: July 04, 2020, 05:47:11 PM by RiverBrewer »
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Offline beerprof

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Re: Phosphortic Acid question
« Reply #2 on: July 05, 2020, 08:52:23 AM »
I purchased a quart of 85% Phosphoric Acid by mistake.  I should have purchased 10% instead.

At the levels that Beersmith recommends for acid addition during the mash step for my size batches (5 to 7 gallon) with my well water the amount required is .04 teaspoon ? obviously impossible to measure.

So I want to dilute the 85% down to a more standard solution of 10% with distilled water that would be easier to handle and measure.

Chemistry and dilution formulas are a long time in my past.  So I thought I would solicit a view on the dilution process.

A strict percentage calculation would yield a .118 conversion factor -- --
   5 ounces of 85% PA to 42 ounces of distilled water

And then I got confused ? are there contributing ions and other factors to this dilution? 

Any help would be appreciated.

You can use M1V1 = M2V2 for the dilution. So if we want to know how much 85% acid to dilute to 100 ounces of 10% acid ??> 0.85(v1) = (0.1)(100) ??> gives us 11.8 ounces. In other words, take 11.8 ounces of 85% acid and dilute it to 100 ounces with water, or take 11.8 ounces 85% acid plus 100-11.8=88.2 ounces water to give you a total of 100 ounces of 10% acid. You can pm me if you need more clarification.

Cheers,
Jeff