[MattyAHA]

Does anyone know if phosphoric acid has a shelflife? i just found a 3-4 year old bottle of 10% phosphoric acid and gonna be brewing soon and wondering if its still good to use, thank you

[dmtaylor]

Great question.  I'll bet it lasts forever...... but I'm not sure.

[Robert]

Good question indeed.  I just found a partial bottle of lactic acid 88% of unknown age on a shelf where it doesn't belong.  Hope a definitive answer comes forward.

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[BrewBama]

Though not phosphoric, I’ve been using the same bottle of lactic acid for several years.  It seems to still be doing its job. My last wort pH was .08 from the Bru’n Water prediction which is close enough in my brewery.


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[mainebrewer]

I have been using a bottle of 85% phosphoric acid for around 6 years. It's still doing its job based on pH results.

[goose]

I have been using a bottle of 85% phosphoric acid for around 6 years. It's still doing its job based on pH results.

Same here!  I have a gallon jug of 75% phosphoric that is about 4 years old and it is still fine to use.  I have also used 10% in the past that was several years old and it was still OK.  Normally acids do not have degrade and the only thing that could contaminate them are exposure to high humidity or contamination from storing a not completely sealed bottle near a strong base like caustic (sodium hydroxide).


If in doubt measure the pH of the acid occasionally and you will see if it has been contaminated and has lost its effectiveness.  If the bottle cap is tight, I am sure you will not see a difference in the pH.

[hopfenundmalz]

A chemist on another forum said that acids are very shelf stable.