Bru'n Water - Strange results in ver. 2.12

[Dave S]

Has anyone used v. 2.12 to calculate sulphuric acid additions? I was set to start a brew on Tuesday, (now deferred to Friday) and B'nW suggested 7.8ml of 25% H2SO4 in the mash water. This seemed like a lot to me but I went ahead with it anyway and, sure enough got an alkalinity of zero or close to it. Plugging exactly the same data into ver. 2.6 gave me 4.1ml. This amount gave me a final alkalinity of 42, aiming for 40. Needless to say, I will be using v. 2.6 for the upcoming brew.

So there is quite a discrepancy it seems between the two versions. I've emailed Martin about it but not yet had a response.

[sllimeel]

Dave

How can you tell what version you have? sorry for the dumb question.

Lee.

[Dave S]

Dave

How can you tell what version you have? sorry for the dumb question.

Lee.

Hi Lee

Not dumb, it's well hidden. Go to the Instructions tab and scroll right to the bottom. BTW, I've sorted this now. It turned out to be the concentration of my Sulphuric acid being incorrectly labeled. Instead of the stated 25%, it is more like 46%. That is Murphy's for ya. So B'n W ver. 2.12 is absolutely fine, (whereas ver. 2.6 is not). Just make sure your acid concentration is correct.

[crookedeyeboy]

Hi Dave

Our SULA25 is not 46% as stated in our technical data sheet:

PRODUCT CODE: SULA25
PRODUCT: 25% SULPHURIC ACID
Composition: Food grade sulphuric acid and water.
Appearance: Clear colourless liquid.
Assay: 25% H2SO4 w/v; 33 - 36% H2SO4 w/w
S.G.: 1.245 – 1.265 @ 20°C

[WallyBrew]

Hi Dave

Our SULA25 is not 46% as stated in our technical data sheet:

PRODUCT CODE: SULA25
PRODUCT: 25% SULPHURIC ACID
Composition: Food grade sulphuric acid and water.
Appearance: Clear colourless liquid.
Assay: 25% H2SO4 w/v; 33 - 36% H2SO4 w/w
S.G.: 1.245 – 1.265 @ 20°C

Let's have a look at what you've put there

33 - 36% H2SO4 w/w with an s.g. of 1.255 average

25% H2SO4 w/v also with an s.g. of 1.255 average

Let's take an average for the weight/weight and call it 34.5

So you have a solution that contains 34.5g of sulphuric in 100g of solution with a s.g. of 1.255
Therefore 100mL of this would weigh 125.5g and contain (34.5*1.255)g of sulphuric. This would be the same as calling it 43.3% w/V.

Not exactly the same as 25% w/V is it?

[Dave S]

Hi Dave

Our SULA25 is not 46% as stated in our technical data sheet:

PRODUCT CODE: SULA25
PRODUCT: 25% SULPHURIC ACID
Composition: Food grade sulphuric acid and water.
Appearance: Clear colourless liquid.
Assay: 25% H2SO4 w/v; 33 - 36% H2SO4 w/w
S.G.: 1.245 – 1.265 @ 20°C

Hi Paul

Well all I can say is that using the figure of 46%, (or more precisely 5.5M) everything works, whereas using the figure of 25% nothing works.

[Eric]

Hi Dave

Our SULA25 is not 46% as stated in our technical data sheet:

PRODUCT CODE: SULA25
PRODUCT: 25% SULPHURIC ACID
Composition: Food grade sulphuric acid and water.
Appearance: Clear colourless liquid.
Assay: 25% H2SO4 w/v; 33 - 36% H2SO4 w/w
S.G.: 1.245 – 1.265 @ 20°C

Paul, this matter was under discussion a full year ago.
Your data sheet states a dosage rate of half a pint per barrel, that is 1 part in 576, to reduce alkalinity by 508 mg/l CaCO3, which is 1.736ml in 1 litre. That means 1ml acid in 1 litre of liquor will reduce alkalinity by 508/1.736 or 292mg/l CaCO3.

The picture is yours in defence of that data, but sulphuric acid of SG 1.26 is 34.6 w/w.
So 1ml contains 0.346 x 1.26 = 0.436g H2SO4. Molar weight of H2SO4 is 98 and of CaCO3 is 100, so 1ml of such acid will neutralise 0.436 x 100/98 = 0.445g or 445mg of CaCO3.

Treating a litre of my tap water with 0.4ml of your so called 25% sulphuric acid dropped its alkalinity by 175mg/l meaning 1ml was capable of neutralising 175/0.4 = 438m/l CaCO3.

While you are on, could you also correct the figure for sulphate after acid treatment, the table is calculated using 98, the molar weight of the acid, not 96, the molecular weight of sulphate.

[crookedeyeboy]

I'd appreciate it if everyone didn't jump on the band wagon and shoot the messenger!
I didn't do the maths and I didn't write the tech sheets

I am in the process of looking into the maths for you.
Thanks

[WallyBrew]

I'd appreciate it if everyone didn't jump on the band wagon and shoot the messenger!
I didn't do the maths and I didn't write the tech sheets

I am in the process of looking into the maths for you.
Thanks

As you still have not managed to do the mathematical calculations here's a bit more for you:

Following on from my calculation giving 43.3%w/V

If you divide 43.3 by the specific gravity of concentrated sulphuric acid (1.84) you get 23.5. This value is the number of mL of sulphuric that weigh 43.3g

Asume that your %w/w is the upper value of 36 not 34.5 then 23.5 x 36 / 34.5 = 24.6

These figures 23.5 and 24.6 would be the V/V figure which maybe is what you are supposed to have instead of 25 % w/V

It is, of course, possible that I may have got all my calculations wrong

[Graham]

I'd appreciate it if everyone didn't jump on the band wagon and shoot the messenger!

Surely, If the messenger speaks with a forked tongue, he should expect to be shot.

It is admirable from a company loyalty point of view to immediately jump to the defence of the company, but it does not do much for customer confidence when that defence turns out to be wrong. It is rather pointless spouting company data-sheets at people when it is that very data that is in question. It would seem better to investigate first, then counter-attack. From what I have read on here over the years, you must be getting quite proficient at dodging arrows.

It seems to me that several of the data-sheets would benefit from being revised from square one; that is, to do all the calculations again, in metric, starting from the product formulation stage. I have noticed a few idiosyncrasies in some of them; some of these are merely the result of cumulative rounding errors often resulting from the conversion between the original ounces or pints per gallon specification and metric. It would be nice to have proper data with proper production tolerances, such as the normality of the acids so that people can work things out for themselves. The data-sheets seem to be dumbed down a little too much; "Technical Data Sheets" that are not very technical. People on here are usually much more astute than they are given credit for.

Also it would be good to have the instructions more intuitive and easier to use.

With AMS for example, it is pointless providing a table that goes the wrong way round. People should already know the amount of alkalinity reduction that they require, so it is counter-intuitive to provide a table that has the AMS dosage as the header when that is the very variable they wish to determine with a fair degree of accuracy. To use that table they have to interpolate between two columns. It is harder and more error prone to do that interpolation than simply to instruct them to divide required alkalinity reduction(as CaCO3) by 184 (or whatever the current divisor happens to be*). After all, they will need to get out the calculator anyway. A similar thing can be done for sulphate and chloride levels.

* On the subject of that divisor; with the original pints/brl spec for AMS the divisor worked out at 184.32, but with the current home brew data sheet it works out at 192. With the latest professional version of the data sheet there is yet a different divisor(182.86). The difference between 184 and 192, being a little over four per cent, may seem trivial, but it smacks of sloppiness and a general lack of precision. It could cause significant overshoot or undershoot when reducing a very high alkalinity water to very low alkalinity, particularly when the, currently unspecified, production tolerances and other sources of error are taken into account. Again it seems to me that this is the result of the complier of the tables or other data taking short-cuts with the calculations, thereby compounding errors.

If one revises a data-sheet, but performs additional calculations using an earlier data-sheet as the basis for those additional calculations (which is what seems to be happening), it is certain to show compounded error creep from one revision to the next, such that after a few revisions the data will have drifted miles away from reality. It seems to me that some of the data originated in the 1950s when there was little more than a slide-rule by which to calculate. It is probably long overdue for some of the products' data-sheets to be recalculated.

[simple one]

I have just roughly tested the capability of my 25% sulphuric acid.
0.2 ml in 1 litre reduced my alkalinity by 105ppm CaCO3. That gives me an acid that 1ml/1litre removes 520 ppm.

Next brewday I'll try it out again on a larger scale to test how accurate my small scale measuring has been.

If I tested correctly, I'm not sure what percentage that makes my acid.

[mozza]

^ this nearly made me wet myself

[Heron1952]

I'd appreciate it if everyone didn't jump on the band wagon and shoot the messenger!
I didn't do the maths and I didn't write the tech sheets

I am in the process of looking into the maths for you.
Thanks

Since Murphys are accredited by
http://www.ukas.com/
I'm sure that they will confirm both SO4 and Alkalinity reports are within the tolerances required of their accreditation!

[barneey]

So simple question then, if I were to buy some Murphy Sulphuric Acid and want to use a "water" calculator what % should I use where it asks me what strength the acid is?

[GrowlingDogBeer]

So simple question then, if I were to buy some Murphy Sulphuric Acid and want to use a "water" calculator what % should I use where it asks me what strength the acid is?

I could tell you. I have some of said Acid and lets just say the figure is nowhere close to 25%.

I will dig out the actual figure in the morning, which I have come to as a result of testing it's ability to remove Alkalinity from my water.

Of course you're bottle could turn out to be a different strength to mine so my figure is probably not helpful.