Sciencemadness Discussion Board

Best neutralizer

chornedsnorkack - 10-1-2015 at 01:43

What would be the best reagent to use to neutralize other reagents?

Acids are commonly neutralized with carbonate solutions. But a problem: carbon dioxide foaming!

There would be no foaming with alkali solutions... but these are themselves aggressive.

A common weak base would be soap... but on neutralizing it precipitates hydrophobic fatty acids.

Now, how about acetate solutions? These would neutralize acids or bases to acetate buffer (around pH 5), and acetate remains in solution... but still, it´s organic. How stable is aqueous acetate to strong oxidants?

So, how about innocuous weak inorganic acids, like phosphate or borate? Could a phosphate buffer safely neutralize both acids and bases, even strong oxidants? One drawback is that metal cations do precipitate insoluble phosphates. But still. Should a laboratory keep phosphate solutions at hand, rater than carbonate?

Yugen - 10-1-2015 at 02:20

Quote: Originally posted by chornedsnorkack  
What would be the best reagent to use to neutralize other reagents?

Acids are commonly neutralized with carbonate solutions. But a problem: carbon dioxide foaming!

There would be no foaming with alkali solutions... but these are themselves aggressive.

A common weak base would be soap... but on neutralizing it precipitates hydrophobic fatty acids.

Now, how about acetate solutions? These would neutralize acids or bases to acetate buffer (around pH 5), and acetate remains in solution... but still, it´s organic. How stable is aqueous acetate to strong oxidants?

So, how about innocuous weak inorganic acids, like phosphate or borate? Could a phosphate buffer safely neutralize both acids and bases, even strong oxidants? One drawback is that metal cations do precipitate insoluble phosphates. But still. Should a laboratory keep phosphate solutions at hand, rater than carbonate?



Sounds like you have a question with no easy answer (there is no cure all reagent for all situations). I guess a good general method would be to use the Henderson–Hasselbalch equation. If you measure the pH of your solution (litmus paper or pH probe) and know what acid you are dealing with (for its pKa value) you can use the equation to add most any strong base to neutralize the solution (e.g. NaOH or KOH).

Rearrange the equation into this form to calculate how much base you need:

10^(pH - pKa) * [Moles of acid] = [Moles of NaOH needed]

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Edit: Typo fixed

[Edited on 10-1-2015 by Yugen]

unionised - 10-1-2015 at 06:31

Quote: Originally posted by chornedsnorkack  
W

How stable is aqueous acetate to strong oxidants?



Fairly stable, but it would be a good idea to neutralise the strong oxidant (with vitamin C or bisulphite etc) before disposal as well.

Personally, I use crushed limestone (which is cheap) in a big enough container to hold the foam.

chornedsnorkack - 10-1-2015 at 10:36

Quote: Originally posted by unionised  

Fairly stable, but it would be a good idea to neutralise the strong oxidant (with vitamin C or bisulphite etc) before disposal as well.


Bisulphite and strong acids will produce volatile sulphur dioxide.

kecskesajt - 27-1-2015 at 10:43

Wash with 2-4 lit. of water and then with KHCO3.If there is only residual acid it wont fizz only a little.I am neutralising my NC with 15 liters of flowing water and then with NaHCO3 and then wash with destillated water.

diddi - 28-1-2015 at 01:03

in .au the standard "spill kit" for acids is just bicarb. cheap, not much foam.

j_sum1 - 28-1-2015 at 02:13

In my little lab space (operating for only a couple of months and still veeery basic) I always have NaHCO3 and NaCO3 in easy reach. I can't remember which one I grabbed when I dropped a litre of boiling H2SO4. My rough concrete floor looked very clean for a while.

When dealing with bases, it is mostly solids that I can sweep up. I think if I was doing anything with any significant volume of strong alkaline solutions I would have dilute acetic acid within reach. Or if I thought solid better I would use NaHSO4 or citric acid handy.

As for oxidisers or reducers, I would choose something suitable before starting.

Like so many questions there is no such thing as a one size fits all solution. It requires a bit of knowledge and forethought to do things safely. I think even staples like vermiculite and sand have limitations and incompatibilities.

The other day I was re-ampouling some Hg and made sure I had my sulfur handy. And I needed it.

That said, having a spill kit with a wide range of applications is sensible. I don't know of anything better than sodium bicarbonate. And sometimes a bit of CO2 evolution is a good thing.

On the other hand, if I was playing with something unfamiliar, phosphorous compounds for example, I would definitely do my safety reading first. I think having to think specifically about safety issues for each project makes me safer. A universal solution would be perfect except for the occasions when it is disastrous.

Amos - 28-1-2015 at 05:02

I pour acids onto a huge pile of ashes in my backyard, where they are easily neutralized by the calcium carbonate. Bases? Vinegar. A variety of gasses can be disposed of or reduced in their ability to harm by reaction with ammonia. Instead of looking for a cure-all, just keep a few different easy-to-find products like these on hand. They're useful enough for syntheses themselves.