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I have about 2g of 99.5% Potassium.

I want to get rid of it, right now it's in a glass jar sealed.

What is the proper protocol? I was going to combust it in water and wash it down the drain but the by-product potassium hydroxide is caustic and hazardous so I don't think that's best.

Could I just throw it away and it goes to a garbage facility where the vial probably breaks and it reacts with rain water and the potassium hydroxide is so small and buried that it never really has an impact?

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  • $\begingroup$ I have my moments ;) good question too! $\endgroup$
    – user15489
    Jul 18, 2015 at 19:27
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    $\begingroup$ Related: How to properly dispose of sodium…or store it properly $\endgroup$
    – user15489
    Jul 18, 2015 at 19:42
  • $\begingroup$ Proper protocol probably varies by country, state/province, and municipality. $\endgroup$
    – Curt F.
    Jul 19, 2015 at 2:36
  • $\begingroup$ I was going to combust it in water and wash it down the drain Absolutely NOT ! Look at this video. It looks they used no more than 0.5 g of potassium. $\endgroup$
    – K_P
    Jul 19, 2015 at 13:20
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    $\begingroup$ Throw it in a lake!. $\endgroup$
    – John Rennie
    Jul 19, 2015 at 15:25

3 Answers 3

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In a suggested lab, the RSC recommends using propan-2-ol:

If there is any unused potassium remaining at the end of the experiment, remove it with the tweezers and place it in a beaker containing about 100 cm3 of propan-2-ol to dissolve away – it will fizz, giving off bubbles of hydrogen. When the fizzing has stopped, dispose of the resulting alkaline solution down the sink flushing it away with plenty of water. The acidic solution remaining from the experiment may also be disposed of down the sink flushing it away with plenty of water.

The same is recommended for sodium.

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  • $\begingroup$ Thankyou! Very good, thanks for the RSC link too. Bookmarked. $\endgroup$
    – Albert Renshaw
    Jul 18, 2015 at 19:58
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I was going to combust it in water and wash it down the drain

No, mixing it with water is a bad idea. Hydrogen gas will be liberated along with heat. In the presence of oxygen and heat the hydrogen will form a combustible / explosive mixture.

Could I just throw it away and it goes to a garbage facility where the vial probably breaks and it reacts with rain water and the potassium hydroxide is so small and buried that it never really has an impact?

No, that's not good either, it will just explode in the dump and start a fire that someone else will have to deal with.

What is the proper protocol?

These two links (link_1, link_2) suggest the same disposal procedure. Link_2 provides more detail. I've reproduced the key part below along with the reactions that take place prior to the final neutralization.

enter image description here

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  • $\begingroup$ Your byproduct in the final equation is potassium hydroxide. If I wanted to get to potassium hydroxide couldn't I just pop it in some water and then have H2O, H2, and KOH ? The whole point of this question was that I wanted to avoid the KOH haha, is this saying to just neutralize the KOH with hydrochloric acid? $\endgroup$
    – Albert Renshaw
    Jul 18, 2015 at 22:32
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    $\begingroup$ Note the last step in the paragraph, neutralization with dilute $\ce{HCl}$. There is little or no $\ce{KOH}$ remaining at the end of the process. In any case you don't want to use water due to a fire/explosion/splattering hazard. $\endgroup$
    – ron
    Jul 18, 2015 at 23:33
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    $\begingroup$ While KOH is produced in both cases, the important part is the rate of the reaction. Water is a much stronger acid than tert-butanol, and therefore the reaction would proceed faster and more dangerously. $\endgroup$
    – March Ho
    Jul 19, 2015 at 4:19
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25% isopropanol (v/v) isopropanol in toluene is the usual means. 2 g potassium is not a large amount. Sodium potassium alloy can also be disposed of this way.

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  • $\begingroup$ Welcome to Chemistry.SE! Take the tour to get familiar with this site. Mathematical expressions and equations can be formatted using $\LaTeX$ syntax. For more information in general have a look at the help center. $\endgroup$
    – Martin - マーチン ♦
    Jul 21, 2015 at 5:04

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