The quality and proper handling of reagents is fundamentally important to experimental success and laboratory safety. The pages on this site provide both basic guidelines for beginning students and hosts forums to provide more specialized information for more advanced researchers.
Shelf Life: If you want to know whether an Aldrich chemical on the shelf is still good, call their customer service number (800-231-8327.) You can give a member of the technical staff the lot number on the bottle, and they will be able to tell you the expected shelf life of that chemical.
When a bottle of a liquid is old, take an NMR to see how extensive decomposition has been. If the compound peaks are dwarfed by impurities, it's time to buy new reagent. If only small impurities are visible, distill the liquid before using it.
Some aldehydes, alkenes and alkynes, especially liquids, are prone to oligimerization. These should usually be distilled before use.
Hygroscopic solids may need to be dried under vacuum before a reaction.
If your experiment is very moisture-sensitive, any bottle labeled "anhydrous" that should be approached with suspicion. Consider distilling it, especially for small-scale reactions.
Really Nasty Chemicals: for a (non-comprehensive and highly opinionated) list, see Highly Toxic Reagents
How to Store Reagent Bottles:
*note: this list does not apply to chemicals that must be stored all by themselves for reasons of reactivity, stench or other special circumstances.
With a parafilmed cap: reagents that might suffer negative effects from the laboratory atmosphere.
Covered with aluminum foil: reagents that are light-sensitive.
In a plastic bag: reagents that smell awful. You might even want to double-bag.
On the shelf: reagents that are
-
thermally stable
- not volatile
- have low or no moisture or oxygen sensitivity
In the desiccator: reagents that are
- thermally stable
- not volatile.
- have some moisture or oxygen sensitivity that could lead to decomposition
In the glovebox: reagents that are
- thermally stable
- not volatile.
- degrade extensively when exposed to the laboratory atmosphere for an extended period of time.
In the refrigerator: reagents that
- are heat-sensitive
- decompose over days or weeks at room temperature
- have a label that says "Refrigerate!" or "Store at > +4 ° C"
- are volatile
- are highly reactive
In the freezer: reagents that
- have a label that says "Freeze"
- are very volatile and stay liquid in the freezer
Very few reagents really need to be in the freezer. If you really want to put a reagent at low temperature, always consider whether the contents of your bottle might freeze and break the bottle.
Didn't find the information you wanted? Post specific reagent questions on Q and A.