Handling 85% Phosphoric acid?

I can get 10 % phosphoric acid from NB for $3.99 with my water roughly 3 batches. I can buy 950ml of 85% for approx. $25.00. Using Bru’n water 10ml vs 80ml for a blonde or amber. My questions.
1, Am I a moron and would I need a hazmat suit?
2, What is the shelf life on Phosphoric acid? I average 25 batches a year.
3, Is there a powdered/dry form that would be safer to handle?

No suit required, but gloves and goggles would be a good idea. It’ll rinse off your skin if you get any on you and I don’t think it’s strong enough to eat through clothes, but if you get some on your pants or shirt, run it under water and then soak in a bucket of soapy water for a little while to neutralize.

It’ll be viscous and weigh almost twice as much as water, so go slowly when weighing it out. If I was using it, I would put a small cup of water on the scale and add the phosphoric to it to dilute, then add the mix to the kettle.

It won’t go bad, but you won’t be using much of it, maybe a teaspoon or a tablespoon per batch.

I wouldn’t want to have it around at 85% even with proper precautions :!: . That probably applies to most home brewers. I googled the MSDS sheet and it says (among many other things) “Engineering Controls: Facilities storing or utilizing this material should be equipped with an eyewash facility and a safety shower. Use only under a chemical fume hood.”

Now, I know from working in several manufacturing plants the past 20+ years that MSDS sheets can sound pretty scary for even tame stuff. But at 85% this causes severe burns and if it splashes in your eyes it can cause blindness. I took enough chemistry in college to know that mixing acid with water to get your dilution can be problematic if you don’t know what you’re doing.

What’s that rule? “Always add acid to water (or was it the other way around?”) If you don’t know what you’re doing, then I’d strongly advise against handling it. Hey, I can change a bulb, but I ain’t rewiring the house. Good luck.

You’ll be fine. Just be smart with it. Wear gloves and safety glasses. When diluting, only add acid to water. It will generate some heat when mixed. Use a large enough glass container to leave a little headspace and mix slowly. It will help to put it on a stirplate to dilute. Ive diluted many different acids in the lab. Just be careful.

Whats scary is a 1000gallon tote of 97% sulfuric acid being pumped into a high pressure/high temperature reactor. :slight_smile:

Proceed with extreme caution, even if it seems like overkill. It’s worth it for anything that can cause permanent damage as a result of one simple, tiny mistake.

By all means use the 85% stuff, so the 10% is in stock when I wander in to NB :mrgreen: I work with “hazardous” chemicals all the time. MSDS are usually way scarier than needed. It’s kind of a write to the lowest common denominator thing. Be carefull with it, use gloves and/or goggles if you are worried, and maybe don’t start drinking until the acid is back on the shelf.

[quote=“WiVikesFan”]…and maybe don’t start drinking until the acid is back on the shelf.[/quote]If you’re drinking while you mash in, you’re in for a loooonnngggg brew day, but yeah, this is great advice. Phosphoric is not as scary to me as bleach is, but using basic precautions with any potentially hazardous material is a good idea. I’ve recently been using 10% phosphoric in the mash and sparge to counter Austin’s tap water pH rather than hauling 20+ gallons of RO water back and forth, but it’s easy to go through 1/3 - 1/2 a small LHBS bottle per brewday and 85% phos is cheap in bulk.

I make enough mistakes without drinking, It makes “cents” to me to take the 8oz. 10% bottle that I got from NB and buy the 85%. carefully add 1oz. to 7oz. of distilled water and use the diluted on brewday. Safer and when the smelly stuff is hitting the fan on brew day safer?


Whats scary is a 1000gallon tote of 97% sulfuric acid being pumped into a high pressure/high temperature reactor. :slight_smile: [/quote]
Yeah I here ya, we had to watch out for something called Oleum, a high consentrate sulfuric acid that will hurt you. Thankfully it’s not used brewing.

Funny. I was ultra paranoid when I started using 75% phosphoric acid. I’m still cautious, but I’ve learned this stuff is not going to burn a hole in my hand. It’s great stuff. Only requires a tiny bit to acidify a 5 gallon batch.

Phosphoric acid is not really a ‘fuming’ acid, so it isn’t as dangerous as sulfuric or hydrochloric acids. It is a fairly strong acid though and demands careful attention at all times.

Using 10% or 85% is not much different from an acidification standpoint. I see that there is a concern over the large volume of 10% version compared to the 85% version. Remember, the only difference is water. In many respects, using the 10% version is more accurate and safer. (its more accurate since a minor error in measurement is magnified for the concentrated acid) But you will end up paying quite a bit more on a molecule to molecule basis. You do have to pay to ship all that extra water, you know.

So if the handling and dosing are a big concern, then using the 10% strength is the way to go. If you have some confidence in your ability to dilute a high concentration acid to a lesser concentration, then you can have the best of both worlds. Buy the high concentration acid and dilute it at home with distilled water to create that safer and easier to dose low concentration acid.

The formula for acid dilution is very simple:

M1 x V1 = M2 x V2

The M variable stands for molarity, but you can use any strength indicator like Percent also. The V variable is the volume.

So if you have 85% acid and want to create 100 mL of 10% acid, the formula would be:

85% x V1 = 10% x 100 mL

performing the algebra results in V1 = 11.76 mL. So you would add 11.76 mL of 85% acid to (100 - 11.76 mL = 88.23 mL) of distilled water to produce 100 mL of 10% acid.

If you are worried about the day to day handling, the dilution route is the way to go. That way you only need to get dressed out in a Hazmat suit a few times, instead of every time you brew. (OK, you don’t really need to wear a hazmat suit, but you do have to use extreme care and protection when handling strong or concentrated acids)


Interesting info. So far I’ve been ok using 70% phosphoric solution, carefully drawing it out of it’s bottle with a 5 ml syringe, being careful not to get any on myself or anything else. I’ve been nailing my desired water profile easy enough this way. I will be even more careful in the future.

I probably shouldn’t say it but I’ve never even handled it with gloves on. I just use a small medicine dropper and am very careful (well except for the gloves). Very small amounts work very quickly in the mash.

I can’t believe you people are using such a dangerous product like phosphoric acid!!!

No one wants to touch sodium hydroxide
for a cleaning product, but you willy nilly toss around and drink phosphoric acid?

Only trained scientist should use phosphoric acid and only little old ladies making home made soap should be using sodium hydroxide.

J/K :stuck_out_tongue:

No, I use sodium hydroxide for my pretzels.

I use the 85% stuff and am careful with handling it, while I use extremely high water temperatures with my exposed flame burner and propane tank in close proximity in my garage… Oh right, the acid is the dangerous part…

I think that dropping acid was something they did in the 1960’s and 70’s.