Phosphoric Acid concentration

[balrog]

It's not c1v1= c2v2, but rather it is c1v1d1=c2v2d2. The density change from d1 to d2 must not be forgotten.

I'm not afraid to be schooled, so school me. [Edit: do I just need to weigh the 1ml of acid?]
1 ml of 85% phosphoric, add to 4 ml (consider it distilled) water, total volume 5 ml.
What % should it be?

 

[Smiling Frog]

I tried to measure it with my refractometer and it wouldn't even register. Double checked with water, spot on. I measured out 10 mL and it weighed 16.16 gms. I make ammunition and I used a powder scale so I am pretty sure about the accuracy. I still have both my hands. Lol That equals 1.61 gm/ml. Since ml = cm3 my sample is about 1.61 gms/cc. According to Steffen's Chemistry pages 85% solution is 1.689 gm/cc. I didn't adjust for temperature and my graduated cylinder is an Amazon cheapy so I am thinking I have 85% solution.
Am I missing something? Please comment.
Thanks! Really appreciate all the great responses!
Also I double checked the pH of the gravity sample I collected yesterday that stalled at 1.031 and the pH measured 3.71, that is after boiling and hops (4 ounces).

If I had to guess, I would guess that whoever diluted the phosphoric acid you have did not mix it well. Probably just added the 85% acid to an appropriate volume of water, but did not mix. If filling is done from the bottom, your bottle came from some of the first ones filled. My guess, there are a lot of people out there with a bottle labeled 10% phosphoric acid that is at a considerably lower concentration.

Another possibility is you are not dealing with phosphoric acid at all, but some other liquid, but your pH measurements seem to suggest that it is a concentrated acid and I am not sure what other concentrated acid would approach that density.

ETA: The assumption is that if you had something like sulfuric acid, a hull melt-through would have been evident .

 

[Smiling Frog]

I'm not afraid to be schooled, so school me. [Edit: do I just need to weigh the 1ml of acid?]
1 ml of 85% phosphoric, add to 4 ml (consider it distilled) water, total volume 5 ml.
What % should it be?

0.85 x 1.689 g/ml x 1 ml = 1.435 g phosphoric acid
4 ml water * 0.997 g/ml (density of water at RT) = 3.988 g
1.435 / (1.689 + 3.988) = .2528 or 25.28%

That's pretty close to the 24.24% prediction from the Refractometer Brix reading.

 

[littlewashingtonbrewery]

Indeed it appears that you are in the density ballpark of 80% Phosphoric Acid (give or take perhaps 5%). If there is a mfg date or lot number on the bottle it might be wise to call the mfgr and let them know. A general recall may be needed here.

This is no lot date on the bottle. I called the distributor right after I got the low reading and they said they just repackage what they buy and insisted by email the next day that purchasing did buy the right concentration and that my meter was wrong. I am going to contact them again but I am guessing there might be some upset brewers in the area. They said nobody else called them with this issue. (Yet?? Am I the first?)

 

[Silver_Is_Money]

85% Phosphoric Acid = 14.6502 Molar = 14.6502M

V1M1 = V2M2
1 x 14.6502 = 5 x M2
M2 = 2.93004 Molar Concentration

MW of Phosphoric Acid = 97.995 g/L
Density of specifically 85% Phosphoric Acid = 1.689 g/CC (=~1.689g/mL)

(4 mL x 0.997g/mL) + (1 mL x 1.689g/mL) = 5mL x D2
Ballpark* D2= 1.1372 g/mL density after dilution
(*with the presumption that 4 mL + 1mL = 5 mL, which for blended chemicals is clearly not always the case)

2.93004 Molar = 1000*(Conc x D2)/97.995 g/L
2.93004 = 1000*(Conc x 1.1372)/97.995
287.1293 = 1000*(Conc x 1.1372)
0.287193 = (Conc x 1.1372)
Estimated Concentration =0.2529
Estimated % Concentration = 25.29%

 

[Smiling Frog]

This is no lot date on the bottle. I called the distributor right after I got the low reading and they said they just repackage what they buy and insisted by email the next day that purchasing did buy the right concentration and that my meter was wrong. I am going to contact them again but I am guessing there might be some upset brewers in the area. They said nobody else called them with issue. (Yet?? Am I the first?)

I have noticed high concentrations of phosphoric acid from some distributors before (which is why I created my Brix > Concentration equation). As you are obviously higher than stated, dilute it with distilled water to achieve a Refractometer Brix reading of 6.3 (or a hydrometer reading of 1.056) and save it. They will likely never admit their mistake (think of their liability if every homebrewer wanted them to reimburse them for a couple dozen batches).

ETA: removed reference to supplier. This issue is probably not confined to a specific supplier.

 

[Silver_Is_Money]

Applying c1v1d1=c2v2d2 we get:

85x1x1.689 = c2x5x1.1372
c2=25.25%

 

[Silver_Is_Money]

Differences are likely due to rounding, plus my assumption of 85% Phosphoric Acid being 14.6502 Molar may be a bit off.

Either way, 25.25% and 25.29% are essentially the same value, as is the 25.28% as calculated by @Smiling Frog.

 

[Silver_Is_Money]

Ah, I found my typo error:

2.93004 Molar = 1000*(Conc x D2)/97.995 g/L
2.93004 = 1000*(Conc x 1.1372)/97.995
287.1293 = 1000*(Conc x 1.1372)
0.287193 = (Conc x 1.1372) This should have been entered as 0.2871293
Estimated Concentration =0.2529
Estimated % Concentration = 25.29%

Therefore:
287.1293 = 1000*(Conc x 1.1372)
0.2871293 = (Conc x 1.1372)
Estimated Concentration =0.2525
Estimated % Concentration = 25.25%

 

[Silver_Is_Money]

They said nobody else called them with this issue. (Yet?? Am I the first?)

Not many use pH meters, so it would generally go unnoticed. I'm more worried about someone being seriously burned, or blinded.

That plus a bunch of people ruining batches of beer and having to toss them....

 

[littlewashingtonbrewery]

I have noticed high concentrations of phosphoric acid from some distributors before (which is why I created my Brix > Concentration equation). As you are obviously higher than stated, dilute it with distilled water to achieve a Refractometer Brix reading of 6.3 (or a hydrometer reading of 1.056) and save it. They will likely never admit their mistake (think of their liability if every homebrewer wanted them to reimburse them for a couple dozen batches).

ETA: removed reference to supplier. This issue is probably not confined to a specific supplier.

I deleted the picture that showed the distributor. Like I said in that post, they are generally a good supplier and may not be their fault. The email the next day told me to check my meter. I sent them another email this morning but I suspect you are right about them not admitting it.
Also, I may be missing something because a SG of 1.056 converts to a Brix reading of 13.8.

 

[Silver_Is_Money]

If all they do is straight repackaging, then perhaps they need to address employee training. Perhaps the employee who was instructed to begin filling 4 Oz. bottles of 10% Phosphoric Acid grabbed a drum of 85% Phosphoric Acid instead. They shouldn't simply say that no mistake is possible because all they do is repackage from bulk. Unless they never purchase the highly concentrated 85% stuff, as for this case they may have ordered a drum of 10% and received a mismarked drum of 85% in error. But then this latter case means your bottle is but one of many....

 

[Smiling Frog]

I deleted the picture that showed the distributor. Like I said in that post, they are generally a good supplier and may not be their fault. The email the next day told me to check my meter. I sent them another email this morning but I suspect you are right about them not admitting it.
Also, I may be missing something because a SG of 1.056 converts to a Brix reading of 13.8.

You are correct in that 13.8 Brix has a SG of 1.056.
What I meant was a Refractometer Brix reading of 6.3 (on your phosphoric acid solution). That is, the Brix reading on the Refractometer when you test your diluted acid. If you give your acid about an eight to one dilution with distilled water, you should get something close to that. By tweaking with either more water or more concentrated acid, you ought to be able to hit 6.3 on the refractometer. Then, as a check, you can test the density with your hydrometer and you should be close to 1.056.

Strictly speaking, Brix is a scale for density where a solution that has a density of pure water is defined as 0 and a solution that has a density of a 10% sucrose solution in water is defined as 10. Many of the refractometers used by homebrewers are calibrated with the Brix scale. They do not measure density, but refractivity, or the refractive index of the sample. I use the term "Refractometer Brix" to mean the Brix reading of such a refractometer. So, when I say the phosphoric acid has a Refractometer Brix of 6.3, I am saying the refractive index of the phosphoric is equal to the refractive index of a sucrose solution with a density of 6.3 Brix. I'll admit, it is a bit sloppy short-hand, but it works for me and I hope most people can understand what I mean.

To add to the confusion, some refractometers will also read in Specific Gravity. I had one of these and I got rid of it. I was always getting confused between the refractometer reading and the density. In my notes, a reading noted as Brix is the reading off the refractometer and a reading written as a SG (such as 1.056) is taken with a hydrometer. Of course, I will convert, so I may have a beer that my notes say had an OG of 13.8 Brix (1.054), which means I measured with my refractometer and converted to SG (using a correction factor of 1.04 because I am measuring wort and not sucrose).

 

[littlewashingtonbrewery]

You are correct in that 13.8 Brix has a SG of 1.056.
What I meant was a Refractometer Brix reading of 6.3 (on your phosphoric acid solution). That is, the Brix reading on the Refractometer when you test your diluted acid. If you give your acid about an eight to one dilution with distilled water, you should get something close to that. By tweaking with either more water or more concentrated acid, you ought to be able to hit 6.3 on the refractometer. Then, as a check, you can test the density with your hydrometer and you should be close to 1.056.

Strictly speaking, Brix is a scale for density where a solution that has a density of pure water is defined as 0 and a solution that has a density of a 10% sucrose solution in water is defined as 10. Many of the refractometers used by homebrewers are calibrated with the Brix scale. They do not measure density, but refractivity, or the refractive index of the sample. I use the term "Refractometer Brix" to mean the Brix reading of such a refractometer. So, when I say the phosphoric acid has a Refractometer Brix of 6.3, I am saying the refractive index of the phosphoric is equal to the refractive index of a sucrose solution with a density of 6.3 Brix. I'll admit, it is a bit sloppy short-hand, but it works for me and I hope most people can understand what I mean.

To add to the confusion, some refractometers will also read in Specific Gravity. I had one of these and I got rid of it. I was always getting confused between the refractometer reading and the density. In my notes, a reading noted as Brix is the reading off the refractometer and a reading written as a SG (such as 1.056) is taken with a hydrometer. Of course, I will convert, so I may have a beer that my notes say had an OG of 13.8 Brix (1.054), which means I measured with my refractometer and converted to SG (using a correction factor of 1.04 because I am measuring wort and not sucrose).

One good aspect of this issue is that I have gained a tremendous amount of information and knowledge from some very smart and experienced people!!
Thank you all for your responses and sharing of information! A lot of what is on the internet could be considered crap but this kind of content is great!

 

[Silver_Is_Money]

73.36 mL of 85% Phosphoric Acid when "made up" to a total of 1 Liter with distilled water = 1 Liter of 10% Phosphoric Acid.

Start with about 700 mL of distilled water in a 1L Flask, and then carefully add the 73.4 mL of 85% Phosphoric Acid to this water, stir, and then lastly top off carefully to 1,000 mL (1 L) with additional distilled water. Stir with a glass rod. Wear all due PPE, and take all due precautions.

C1xV1xD1 = C2xV2xD2
0.85 x 0.07336L x 1.689 g/CC= Conc x 1L x 1.0532 g/CC
Conc = 0.09999932
Conc% = 9.999932% = 10% (when rounded)

 

[jerrylotto]

Hey - if I can buy 85% phosphoric acid for the cost of 10%, I'm in. Who is the vendor?

 

[balrog]

Hey - if I can buy 85% phosphoric acid for the cost of 10%, I'm in. Who is the vendor?

I got mine on amazon, "Duda Energy". Pictured in post #23 above.

 

[jerrylotto]

I got mine on amazon, "Duda Energy". Pictured in post #23 above.

I was asking the OP from where he got the mislabeled acid.

 

[littlewashingtonbrewery]

Hey - if I can buy 85% phosphoric acid for the cost of 10%, I'm in. Who is the vendor?

A lot of my brewing friends routinely use 75% solutions. Out of the 4 bottles I bought at the same time I have checked 2. If all 4 are high % solutions I have enough acid for life! I am going to dilute the acid I got and see if I get the predicted results in terms of gravity and compare my solution to some known 75% solution that a friend has. I want to be as certain as possible before I use it again. I am already dumping one batch, I don't want to dump a second.

 

[littlewashingtonbrewery]

I was asking the OP from where he got the mislabeled acid.

I bought it about 8 weeks ago. It is hard to say if they still have any more. I am going to call the retailer today and talk to him about what happened.

 

[jerrylotto]

A lot of my brewing friends routinely use 75% solutions. Out of the 4 bottles I bought at the same time I have checked 2. If all 4 are high % solutions I have enough acid for life! I am going to dilute the acid I got and see if I get the predicted results in terms of gravity and compare my solution to some known 75% solution that a friend has. I want to be as certain as possible before I use it again. I am already dumping one batch, I don't want to dump a second.

Instead of just measuring and adding based on an assumption of the initial concentration, just titrate with it until you hit the target pH. If it is easier, dilute it first. The concentration really doesn't matter, it is the result that counts!

 

[Silver_Is_Money]

For those in the UK: Diluting 75% or 85% Phosphoric Acid to 30% brings its ( ballpark pH 5.4 specific) acid strength (in units of mEq's/mL) right in line with CRS/AMS, wherein CRS/AMS data for carbonate reduction can then be used with 30% Phosphoric.

 

[Silver_Is_Money]

Instead of just measuring and adding based on an assumption of the initial concentration, just titrate with it until you hit the target pH. If it is easier, dilute it first. The concentration really doesn't matter, it is the result that counts!

The MAJOR problem here is that Phosphoric Acid is triprotic, plus it is a weak acid, meaning that at every pH along the pH scale its mEq/mL acid strength is different. At pH ~9 it is ~twice as strong as it is at pH ~5.4, and at ballpark pH 14 it is ~three times stronger than it is at pH 5.4. All weak acids strengths change with respect to the chosen pH target.

For this reason, it is not really possible to make known strength concentrations of Phosphoric Acid (or Lactic Acid, etc...) in terms of Normality. Such as 0.1N, or 1N, etc...

OTOH, strong acids and strong bases can be made into quite useful "Normal" (or normality, N, or Equivalent, or milliequivalent) strengths, since they dissociate fully at any pH. HCl, H2SO4, and HNO3 are strong acids. AMS/CRS is a blend of strong acids, so at any pH its strength is ~3.66 mEq/mL. For this one the strength does not change with pH.

 

[Silver_Is_Money]

Triprotic 10% Phosphoric Acid's mEq/mL strength at a few pH's:
@ pH 4.3, mEq's/mL = ~1.0681
@ pH 5.0, mEq's/mL = ~1.0796
@ pH 5.4, mEq's/mL = ~1.0903
@ pH 6.0, mEq's/mL = ~1.1368
@ pH 7.0, mEq's/mL = ~1.4844
@ pH 9.0, mEq's/mL = ~2.1325
@ pH 12.0, mEq's/mL = ~2.4969
@ pH 14.0, mEq's/mL = ~3.2016

Monoprotic 88% Lactic Acid's mEq/mL strength at a few pH's:
@ pH 4.0, mEq's/mL = ~6.8323
@ pH 4.3, mEq's/mL = ~8.3465
@ pH 5.0, mEq's/mL = ~10.9859
@ pH 5.4, mEq's/mL = ~11.4515
@ pH 6.0, mEq's/mL = ~11.6971
@ pH 7.0, mEq's/mL = ~11.7733
@ pH 9.0, mEq's/mL = ~11.7817
@ pH 12.0, mEq's/mL = ~11.7911

As always: I ask that someone (or preferably multiple someones) independently verify the above information. It could easily be incorrect. Use at your own risk. YMMV

 

[jerrylotto]

The MAJOR problem here is that Phosphoric Acid is triprotic, plus it is a weak acid, meaning that at every pH along the pH scale its mEq/mL acid strength is different.

Which does not contradict what I said about titration, If anything, I believe this supports it.

 

[Silver_Is_Money]

For those desiring to make 1L of 30% Phosphoric Acid from 75% Phosphoric Acid:

75% Phosphoric Acid:
Density = 1.579 g/mL
C1 = 0.75
V1 = V1

30% Phosphoric Acid:
Density = 1.1805 g/mL
C2 = 0.30
V2 = 1.000

C1xV1xD1 = C2xV2xD2
0.75 x V1 x 1.579 = 0.30 x 1.000 x 1.1805
1.18425 x V1 = 0.35415
V1 = 0.29905L
V1 = 299.05 mL

Make up 299.05 mL of 75% Phosphoric Acid to a total volume of 1 Liter with distilled water. (never add water to acid) You will then have 1L of 30% Phosphoric Acid, which should be ~3.66 mEq/mL in acid strength at ~pH5.4 (or very much like CRS/AMS at pH 5.4)

NOTE: To do the same with 85% Phosphoric Acid, make up 246.7 mL of 85% Phosphoric Acid to a total volume of 1 Liter with distilled water. (never add water to acid)

 

[Silver_Is_Money]

The reason why you never add water to a concentrated acid is that it evolves heat rapidly, which can cause instant local boiling, and thereby instant local splashing of both boiling hot and concentrated acid.

 

[littlewashingtonbrewery]

I think I pretty much confirmed I got 85% solution acid. I brewed yesterday and entered 85% in my water software and the mash pH came out as predicted. The batch I made that prompted this thread never fermented below 1.032 and tasted so bad I dumped the whole batch. Not salvageable.

 

[Smiling Frog]

I think I pretty much confirmed I got 85% solution acid. I brewed yesterday and entered 85% in my water software and the mash pH came out as predicted. The batch I made that prompted this thread never fermented below 1.032 and tasted so bad I dumped the whole batch. Not salvageable.

You should send your recipe to the supplier and ask them to replace the ingredients. Obviously, they aren't going to pay for labor, but they should be on the hook for the ingredients. By now, they should have been able to find out what went wrong, whether it was simply a mis-labeled bottle or poor procedures.

 

[littlewashingtonbrewery]

You should send your recipe to the supplier and ask them to replace the ingredients. Obviously, they aren't going to pay for labor, but they should be on the hook for the ingredients. By now, they should have been able to find out what went wrong, whether it was simply a mis-labeled bottle or poor procedures.

I talked to the retailer but just to give him a heads up about the problem. What I got was not their fault so I am not going to ask them for compensation. We discussed the issue and we don't think the wholesaler/repackager will ever admit responsibility because of liability. The last email I sent to the wholesaler went unanswered so I will just be happy with what I learned and my lifetime supply of acid. Lol