testing strength of phosphoric acid

[paulg]

in my last brew ,the first with phosphoric acid 75% I used bru n water to calculate my addition to give a mash ph of 5.5 when Imeasured it I measured 5.0ph
I have checked my grain input and mineral additions (see previous post below) and can see no mistakes,so I wonder if my acid is not 75% is ther a way to test this.
I have a hanna tester for hardness which measured my water at 210 it was 218 when measured by murphys 2 years ago.
I previously used crs and bru n water appeared to calculate correctly my mash ph (as best I could tell with strips I now have a ph meter which I did calibrate before the last brew
thanks in advance
Paul

[Dave S]

Did you enter the EBC values for the Mask grains? Even so, you can't be sure they'll be accurate. Did you measure the alkalinity after the phosphoric additions?, (you need to give a good stir and leave for 10 mins or so). That will tell you if the percentage dilution is correct if it agrees with the calculated value.

[barneey]

Paul,

Get yourself a known volume of water, test the Alkalinity. Say 10 litres

Add an amount of acid to the above. say 5ml

Test Alkalinity again of treated water.

Post both the alkalinity readings on here.

Cheers

[Heron1952]

I've had the same/similar problem with 75% from APL. Indicator in Salifert turned pink immediately after treatment had to dilute by about 20%
OK
pretreated Salifert test gave 160mg/l lower than usual it has to be said.
Added 2.5ml alleged 75% phosphoric to 5l Treated water.
second Salifert turned red immediately on addition of 1 drop of KH-ind without addition of any KH from 1ml micro syringe
Either I'm testing wrongly or this 75% phosporic isn't what it says on the tin!!
Paul who was you Phosphoric supplier?

[WallyBrew]

I've had the same/similar problem with 75% from APL. Indicator in Salifert turned pink immediately after treatment had to dilute by about 20%
OK
pretreated Salifert test gave 160mg/l lower than usual it has to be said.
Added 2.5ml alleged 75% phosphoric to 5l Treated water.
second Salifert turned red immediately on addition of 1 drop of KH-ind without addition of any KH from 1ml micro syringe
Either I'm testing wrongly or this 75% phosporic isn't what it says on the tin!!
Paul who was you Phosphoric supplier?

You are unlikely to be able to get hold of phosphoric at a strength greater than 85% and this is known as syrupy phosphoric acid.

[Heron1952]

I'll test again let's hope it is actually Phosphoric!!

[paulg]

heron 1952
the same acid as you APL from ebay
http://www.ebay.co.uk/itm/121176548907? ... 1439.l2649


just off to test and post water results

[paulg]

ok so the results

10 litres water wieghed on scales = 10 kilos
tested 216 with my hanna alkalinity tester (this is close to my murphys test 2 years ago = 218)
added 5 ml phosphoric acid with lab grade graduated pipette supposedly 75%
retest = 0 machine doesnt go below 0 I think

so reweighed 10 kilos water retest 216
added 2.5 ml acid
tested = 56

dont know what that means strength wize but there it is

onyone?

[Heron1952]

That sounds very similarly in order of magnitude!! I'm off to check again!

[barneey]

according to my calculator 2.70ml of Phosphoric @75% should reduce the alkalinity of 10 litres from 216 to 56 so the strength would seem to be correctly labelled.

[Mr. Dripping]

I've the same acid and I've used it in 4 brews without any issue.
Can't vouch for it being the same batch of course, but it is from the same supplier.
ATB

[Heron1952]

OK so this is probably the same.
If so I have been using Bruin Water wrongly.
I tested with a Salifert kit.
Initial water .33ml reagent gave 3.7meq/L = 185mg/L as CaCO3
initial treatment with 1.25ml of 75% phosphoric in 5 litres turned pink straight away with KH-ind 1 drop
Diluted 2.5 of this treated with 2.5 untreated retest
.62ml reagent gave 2.05meq/L = 102mg/L as CaCO3
Bru'n Water, Me, or Phosphoric and in the light of Barneey's comment and Mr Dripping's I think I need revisit my Bru'n Water inputs

[Heron1952]

Bru'n water seems to be telling me that 5 litres at 185ppm as CaCO3 needs 1.29ml 75 % phosphoric to give me a water alkalinity of 27.5 ppm

[WallyBrew]

Heron1952

From what you have posted, and 1.29mL is correct, you need to do a bit more stirring to ensure complete reaction.

If your original water had no alkalinity it should have given 92.5 on blending with untreated.

[Heron1952]

Heron1952

From what you have posted, and 1.29mL is correct, you need to do a bit more stirring to ensure complete reaction.

If your original water had no alkalinity it should have given 92.5 on blending with untreated.

Sorry I 'm still confused.
Bru'n tells me with 1.29ml I will still have some alkalinity yet if when I added 1.25 ml I had none at all.
Or is it that if I didn't stir enough their was still acid that had not reacted and this was affecting to test solution? giving an over acidic reading? When there was still plenty of Hardness still to react with it