[AlphaScent]

Why would it be better to make lithium amide in situ with lithium and iron (III) nitrate in liquid ammonia if you have powdered lithium amide available??

[discodermolide]

Here is a patent that may give you a pointer to this answer.
http://www.google.com/patents/US4206191

[AlphaScent]

I have only gotten a page in.  It would seem that with making it in situ you will evolve hydrogen.  This seems to be a con to just adding the powder.  Have more to read.

[discodermolide]

I didn't read much but it seems to be about particle size.
Stick to the stuff from Aldrich.

[AlphaScent]

I guess I understand that they make a fine material to not allow impurities. 

My question was regarding why would a chemist make his own lithium amide in situ with lithium, iron (III) nitrate and liquid ammonia instead of just using the nice, pre-made, fine powder we have from aldrich.  Particle size may have something to do with it.  They made it with a two-phase system that incorporated toluene as a reactant.   

Just because I watched it happen in the lab yesterday.

[discodermolide]

Probably a question of purity. Commercial lithium amide may contain traces of LiOH.
I sometimes made my own LDA from Li metal. In those cases it gave a better reaction than the commercial stuff.
And you can make the whole soup much more concentrated.

[AlphaScent]

I thought that it had to do with the commercial stuff "going bad" and my colleague confirmed it as well as you Disco. 

He is using it on propargylic alcohol.  He says making it fresh works best for propargylic alcohol in particular.