# Cheap but efficient disinfectant / biocide for home lab

EDIT

I am forced to reword my question about a chemical mixing ratio.

I have seen in Wikipedia that peroxide ($$\ce{H2O2}$$) and Acetic Acid can be mixed to Peracetic acid - this is an equilibrium.

I have also seen in Wikipedia that peracetic acid mixed with acetic acid will be explosive - in other words: If I don't get the mixing ratio just right then the "peracetic acid" will actually be "peracetic acid dissolved in acetic acid". I need to avoid this situation.

I have also read in Wikipedia that "thinning" the peracetic acid will shift the equilibrium and so this might end up in an explosive solution - I need to avoid this.

I have also seen at amazon.de that peressigsäure/alkohol is widely used as a disinfectant and I suppose the ratio of ethanol should be at 69% in order to kill most any microbes.

I need to mix a weak solution of $$\ce{H2O2}$$ and acetic acid and 69 % ethanol so that the peracetic equilibrium is held to be non explosive. And I also need to mix a more potent solution of $$\ce{H2O2}$$ and acetic acid and 69 % ethanol so that again, the peracetic equilibrium will fit and not be explosive.

As far as I understood it is not done by having the potent solution in the fridge at 0 degree Celsius and on demand simply thinning the potent solution to a weaker disinfectant - the peracetic equilibrium would then shift and it might become explosive.

Sorry, I am not really fit to calculate concentrations in Vals and Mols - but I could of course deal with any complex mathematical formula (on paper or on the calculator - or I could even code a small mixing calculator in java or c#).

So I would ask you to give me the right formula for my problem:

Component A = 12 % $$\ce{H2O2}$$

Component B = 20 % Acetic Acid

Component C = 98 % Ethanol

Component D = $$\ce{H2O}$$

AND I need 1 liter of mixture so that Alcohol appears with 69 VOL % and that peracetic acid appears with $$x$$ % ($$x$$ between 2 and 10) and no acetic acid will be in the mixture aside from the equilibrium.

I could then simply vary the $$x$$ (the conecntraction of peracetic acid) in the formula and mix as needed.

please, show me how to calculate the concentrations. thanks!

• I'm voting to close this question as off-topic because this belongs on biology SE or other site - it's not about chemistry – Buck Thorn Jun 6 at 20:49
• well the interactions between ehtanol and peroxide and acetic acid is definatly about chemistry - or should the mathemacician tell me how these chemicals will react? please suggest where I should ask this. thanks – Gerald Trost Jun 7 at 15:58
• it is not primarily about killing life - I know how to kill contaminations. it is a question about the mixing rate so that peroxide and acecic acid will stay in the proposed equilibrium and that not highly explovives will happen by accident. This is 100% a question about chemistry – Gerald Trost Jun 7 at 16:04
• Mixing rate (how fast) or mixing ratio (how much)? Check out the MSDS for the product TM peracid 15 (English ; German). They don't use any alcohol, and have a whole range of substance that are incompatible. – Karsten Theis Jun 7 at 20:57
• It should be simple once you know tha safety limits. Besides, are you sure that bleach won't be ok? Just to be sure you do not overshoot. – Alchimista Jun 10 at 9:28

The Amazon website gives the composition of Peressigsaure/Alkohol: Inhaltsstoffe pro 100g:

● 19g 2-Propanol

● 5g Ethanol

● <1% Wasserstoffperoxid

● <1% Peroxyessigsäure

● <1% Essigsäure

Working time 30 seconds, shelf life 12 months.

Don't expect that H2O2 plus acetic acid to give peroxyacetic acid. The full Wikipedia reference is:

Peracetic acid is produced industrially by the autoxidation of acetaldehyde:[2]

O2 + CH3CHO → CH3CO3H

It forms upon treatment of acetic acid with hydrogen peroxide with a strong acid catalyst:[3]

H2O2 + CH3CO2H ⇌ CH3CO3H + H2O

Making the peroxy acid can be done from acetic acid, but requires a strong acid catalyst (to generate CH3CO+).

So, you will have to get peroxyacetic acid from somewhere in some form, in addition to your other chemicals. Duplicating this formula requires more isopropanol than ethanol, but either alcohol should perform equally.

An overview document titled Chemical Disinfectants at https://www.cdc.gov/infectioncontrol/guidelines/disinfection/disinfection-methods/chemical.html mentions two chemical sterilants are available that contain peracetic acid plus hydrogen peroxide (i.e., 0.08% peracetic acid plus 1.0% hydrogen peroxide [no longer marketed]; and 0.23% peracetic acid plus 7.35% hydrogen peroxide. This document also lists the benefits of H2O2, peracetic acid, alcohol(s) and chlorine bleaches. And formaldehyde! About peracetic acid, it says: It is considered unstable, particularly when diluted; for example, a 1% solution loses half its strength through hydrolysis in 6 days, whereas 40% peracetic acid loses 1%–2% of its active ingredients per month.

As regards explosivity, a document of ECETOC at http://www.ecetoc.org/wp-content/uploads/2014/08/JACC-040.pdf gives the formulas of two cleaners as:

1: PAA 15%,H2O2 23%,HOAc 16%,H2O 45% and

2: PAA 15%,H2O2 14%,HOAc 25%,H2O 42%.

I gather from these two formulations that they and anything less in H2O2 or PAA would not even remotely be explosive. No alcohol was listed in these formulations.

Now if you could obtain either of these concentrated sterilants, you would have a reasonable ratio of peracetic acid, H2O2 and acetic acid. The only item missing would be the alcohol. Let's use ethanol, at 70% (or 69%, if you must). The peracetic acid cleaners would have a good shelf life because of their high concentrations. When you need to make up some sterilant, you could take ~800 grams of ethanol and add ~350 grams of the cleaner you choose to get 1 L of final sterilant (density ~1.150 g/cc), which will be 69-70% ethanol, 4.5% PAA, 4.3-7% H2O2, 7.6-4.9% HOAc, remainder H2O.

These levels are 5 or more times higher than the concentrations listed for Peressigsaure?Alkohol Pro, so you could consider adding much less of the peracid cleaner to get in the range of 1% PAA and H2O2.

Overall, it seems that H2O2 by itself is good at killing bacteria, and so is alcohol, by itself, and so is peracetic acid, by itself, but PAA is not stable for long at low concentrations (12 months at 1%??).

And perhaps it would be easier to buy the Peressigsaure/Alkohol Pro, or one of the other sterilants offered by that company, because it already comes in a spray bottle.