The main problem on collecting chemical waste are possible reactions.
- Unfortunately generally you do not know what is still in the canister. So take care about that what you like to add to the content.
The actual hazard is regulated by the amount of the new added compound. The following relation applies:
If there is a risk of a reaction, give only a small amounts into the canister and vice versa. For example the used solvents of a chromatography may be put into the canister all at once. Are there more than one user and every user is disposing "anything" into the canister or if you are just going to dispose reagents which you do not need any more you should be carefully.
In fact you want that nothing will react in the canister!
But count that there will often occur some reactions. Normally you will not recognize this because the reactions are slow and light. Let's make a new point:
You do not want a vigorous reaction in the canister!
To ensure this follow these hints:
- On collecting chemicals in the solvent canister never screw on the seal tightly!
If it happens that a reaction occurs which develops gas, the gas may then escape from the canister. It is best to screw the seal only a little bit to minimize evaporation of the content. Since the plastic canisters are too light weighted commercial funnels designed for collecting chemical waste are not suitable. (...and are also very expensive.)
- When the last waste has been added do not screw the seal at once but wait instead.
Give every reaction the chance to fade away. If you are really a good chemist srew tightly for a moment, then mix the content thoroughly by turning, wiping or rolling the canister and then immediately reopen the seal. Leave it standing overnight and then you will be sure that nothing will be still reactive.
- It is a good idea to mix the content also during the collection of the waste from time to time.
Otherwise the waste can persist in layers which will mix up, when you move the canister. Consider that a "scientific reaction" is generally stirred with a magnetic stirrer. Why should compounds in the waste react smoothly without stirring only because stirring of a waste does not make fun?
- Place the canister in a safety pan.
An accident should not be followed by an even bigger accident.
- Never put carbonate solutions into the canister.
Solvent waste often contains compounds which may be hydrolized to acids (example: Halogene alkanes). The mixture may become then more and more acidic. With carbonate present this will develop carbon dioxide gas. Since this may also happen when the canister is full and then tightly closed the canister may then explode.
- Put reactive componds either only in small portions into the canister or do not put them into the canister!
If you dispose chemicals into the solvent canister it is more safe if you reserve time for this job! If a big amount has to be disposed think about stirring. Alternatively you may dispose every organic chemical in a separate bottle.
Yes! You are a chemist! You will be able to design a reaction, which will decompose a reactive compound! But generally you need further chemicals for the designed reaction. What about the costs for these chemicals? Consider that in this case also the total weight of the waste will increase and this will also increase the costs. If other chemicals than water are needed generally a reaction to dispose a chemical is not profitable. Consider also the effort needed!