# How to dispose of pure potassium

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?

• I have my moments ;) good question too! – user15489 Jul 18 '15 at 19:27
• – user15489 Jul 18 '15 at 19:42
• Proper protocol probably varies by country, state/province, and municipality. – Curt F. Jul 19 '15 at 2:36
• 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. – K_P Jul 19 '15 at 13:20
• – John Rennie Jul 19 '15 at 15:25

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.

• Thankyou! Very good, thanks for the RSC link too. Bookmarked. – Albert Renshaw Jul 18 '15 at 19:58

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.

• 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? – Albert Renshaw Jul 18 '15 at 22:32
• 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. – ron Jul 18 '15 at 23:33
• 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. – March Ho Jul 19 '15 at 4:19

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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