Using phosphoric to acidify sparge water

[kaiserben]

I bought some "pure" phosphoric acid (which is actually 96% phosphoric & 4% filtered water) because I wanted to try acidifying my sparge water.

For 15L of sparge water (which is what I'd normally have) I'd need about 0.5ml of that 96% phosphoric.
Because 0.5ml is such a small amount and it'd be difficult to add the exact amount, I'd like to dilute some solution to make it easier to work with.

What I want to know is:
Firstly, is there a point at which you can dilute phosphoric acid too much (that it becomes unstable for long term storage)?

Ideally I'm hoping I can simply dilute an amount that will allow me to add more like 5ml at a time. I think that means a 15% phosphoric acid solution would be ideal. And if my chemistry/mathematics is correct that'd mean I could make an easier to work with batch by adding 7.8ml of the 96% acid solution to 0.5L of filtered water to have 0.5L of a 15% solution. Could someone please confirm I have this right?

0.5L of 15% acid solution would last me 100 sparge water additions, so hopefully the solution would be stable for a few years if kept out of the sunlight?

 

[Coodgee]

Just get a syringe with .1 ml graduations. That's what i use. Very accurate

 

[Bribie G]

Chemists sell syringes without the needles, from tiny to scary, just let them know it's for craft purposes - dress nicely and don't fidget too much, or let your eyes roll around wildly.

 

[Coodgee]

Chemists sell syringes without the needles, from tiny to scary, just let them know it's for craft purposes - dress nicely and don't fidget too much, or let your eyes roll around wildly.

Nah man you can be a twitching, barefoot meth head and they'll sell you a sharps kit no questions asked!

 

[kaiserben]

Haha.

Perfect! I didn't think of that. I've grabbed a syringe from a chemist before (just not with as small as .1ml graduations) to use as a ghetto nitrogen carbonation tool. So I'll go back and try not to act too suss.

 

[Coodgee]

I use the one the vet gave me to dish out medication to my dog when he had kennel cough. My guests all have very clear throats by the end of the night.

 

[damoninja]

Chemists sell syringes without the needles, from tiny to scary, just let them know it's for craft purposes - dress nicely and don't fidget too much, or let your eyes roll around wildly.

Drawing attention to the fact it's not for drugs is only going to make them think it's for drugs.

 

[timmi9191]

+1 for 1ml syringe, but...

0.5ml of 96% for 15l seems a lot, I use 0.8ml of 96% for 40l.

What are you using to do your calculations?

 

[Lyrebird_Cycles]

Ideally I'm hoping I can simply dilute an amount that will allow me to add more like 5ml at a time. I think that means a 15% phosphoric acid solution would be ideal. And if my chemistry/mathematics is correct that'd mean I could make an easier to work with batch by adding 7.8ml of the 96% acid solution to 0.5L of filtered water to have 0.5L of a 15% solution. Could someone please confirm I have this right?

No it is not correct. If you made up the solution as suggested it would end up at about 2.7%.

You have made two errors: one is a simple order of magnitude error, the other is that you have not accounted for the density of the phosphoric acid solution.

96% W/W phosphoric has a density of about 1.83 so it's 1.75 g / ml H3PO4. Accordingly you need to add 43ml to make up to 500 ml at 150 g/l.

 

[kaiserben]

+1 for 1ml syringe, but...

0.5ml of 96% for 15l seems a lot, I use 0.8ml of 96% for 40l.

What are you using to do your calculations?

For that 0.5ml figure I checked in both Bru'n Water and Brewer's Friend. I suppose the calculations must take into account the total volume (mash & sparge), which for me is 32L (17L mash + 15L sparge).

If anyone wants to double check if I'm doing something wrong, these are the values I've taken from the water report for my area:

Ca = 14.3 ppm
Mg = 4.7 ppm
Na = 13.95 ppm
Cl = 27.9 ppm
SO4 = 7.95 ppm
Alkalinity = 35.5 (CaCO3 ppm)
pH = 7.9

I only want to use the phosphoric acid for sparge water. For mash water I'll use calculated amounts of brewing salts and occasionally acidulated malt.

 

[timmi9191]

Your water has ALOT more alkalinity than mine, so your measurements are probably fine.

 

[sp0rk]

Nah man you can be a twitching, barefoot meth head and they'll sell you a sharps kit no questions asked!

We've sold them out of our pharmacy at work (an animal hospital) from time to time
Once had 2 sketchy looking characters telling us they needed a certain needle for injecting something into their horse's eye
The pharmacy manager came back out with the correct needle and dosing gear for injecting into an eye, saying she wouldn't sell them a normal needle if that's what they were doing.
Yeeaaaaah, they left without any needles

 

[Coodgee]

We've sold them out of our pharmacy at work (an animal hospital) from time to time
Once had 2 sketchy looking characters telling us they needed a certain needle for injecting something into their horse's eye
The pharmacy manager came back out with the correct needle and dosing gear for injecting into an eye, saying she wouldn't sell them a normal needle if that's what they were doing.
Yeeaaaaah, they left without any needles

Was it this guy?

 

[Lyrebird_Cycles]

15L sparge).

Alkalinity = 35.5 (CaCO3 ppm)

I only want to use the phosphoric acid for sparge water. For mash water I'll use calculated amounts of brewing salts and occasionally acidulated malt.

15l @ 35.5 ppm = 0.53 g CaCO3, MW = 100 that's about 5 mmoles = 10 mEq.l

0.5 ml @ 1.75 g/l = 0.875 g H3PO4, MW = 96 that's about 9 mmoles = 27 mEq.l

I think 0.2ml should do you.

 

[Matplat]

Was it this guy?

edaee4291de3d2a1fe7fa335e08314ed.jpg

I think that's the scariest thing I've ever seen.