[seker2k]

What does it mean to "Distill over KOH" or to "Distill onto KOH", or some other reagent?
How about "dried and distilled over KOH"?

How about "reflux over KOH"?

I understand the concepts of basic distillation and reflux, what I would like to understand is the what, why, how and when of a few examples for the above questions.

Just looking to understand the basic concepts.

[Borek]

Just add KOH pellets to the flask.

[seker2k]

OK, but why would someone need to do something like that? Wouldn't that possibly contaminate the final product? BTW, thanks for the answer.

[sjb]

Typically you'd do this to get rid of acidic byproducts or similar, or indeed reflux over KOH when you need basic conditions for your reaction.

[Borek]

Wouldn't that possibly contaminate the final product?

Quite the opposite - such techniques are used when procedure done without the solid (be it KOH, or metallic Zn, or something else) will yield contaminated product.

[seker2k]

Thanks, and if one was to distill "onto KOH", they would place the KOH pellets in the receiving flask, is this correct? Or does "over" = "onto"?

[sjb]

"Distill onto" would mean having the base in the receiver flask