[Urbanium]

We have a 1 yr old bottle of 1M solution of lithium aluminium hydride in THF in our lab. It has been opened once, small quantity was used and the rest stored in the fridge all the time since then. How can I check if it's still useful? Should it be?

If it's wasted i.e. useless, I have one procedure in which addition of a solution of LAH in THF by a funnel is required. Since I never used LAH previously, is there any special thing or some good advice I need to take care of when preparing a solution of LAH in THF?

[TheUnassuming]

Its hard to say whether or not it will still be good.  The easiest way to check will be to run the reduction on a small scale and see if it works.   
If you need to make it yourself, just make sure everything is dry and under inert atmosphere.  If you don't have an SDS system, redistill the THF before use. 

[Dan]

How can I check if it's still useful?

I'd imagine LAH solutions go cloudy if they're degraded (due to formation of aluminium (hydr)oxides). If it's clear, it's probably worth a shot. I very rarely use LAH, so I might be writing complete rubbish.

[tomek]

Take a small aliquot and add water drop by drop and see if it fizzles and white precipitate forms. This will tell you if there's some LAH left but you'll be clueless if it's still 1M concentration. You can then try and use excess of the reagent or simply run reaction on a small scale as TheUnassuming suggested.
Recently I've been working quite a lot with LAH and usually I put it in THF (weigh it without any delay), bring the mixture to a gentle reflux and add whatever I want to reduce (everything dry and under inert atm). I dry THF with KOH then distill it, then dry rigorously with Na/Benzophenone, distill again and use as such. Good way to work up your reaction is to quench it with x ml of water, x ml of 15% NaOH and 3x ml of water (where x is amount of grams of LAH used) this should give precipitate which is easily filtered.

[Urbanium]

Thanks for the answers.

The solution we have is crystal clear. I will however run the reaction on small scale to test it.

The only thing that bothers me here is that you mention "intert atmosphere". How the heck am I supposed to add this solution via addition funnel over a period of 30 minutes under inert atmosphere?

Is there such a high chance a solution of LAH in THF is going to decompose so quickly (or in a worse case, self-ignite) if in contact with air all the time?

[Dan]

The only thing that bothers me here is that you mention "intert atmosphere". How the heck am I supposed to add this solution via addition funnel over a period of 30 minutes under inert atmosphere?

Something like this:

[BobfromNC]

Is there such a high chance a solution of LAH in THF is going to decompose so quickly (or in a worse case, self-ignite) if in contact with air all the time?

Yes, it can catch fire readily, I have seen at least one roaring LAH blaze, which was due to someone adding it as a solid but not under nitrogen.  Not the way to start the day.

The key to LAH reactions is to transfer the LAH solution to the dry flask first (use a syringe or cannula), under inert atm., and then add the substrate dropwise from an addition funnel, which allows you to control the addition rate well.  In all but a few cases, it is better to have the substrate in an excess of LAH from the start.   You might even need to to cool the LAH soln. before adding the substrate, depending on the compound and the scale.  Once the substrate is all added, let the reaction go to completion, then quench the remaining LAH with EtOAc (dissolved in THF, added dropwise also.), then do the Fieser workup or a variation of it (if not sure, google it).  If the scale is over a few grams of LAH, then fire is a more serious risk, and some experienced help is best.