Soxhlet extraction condenser - addition of compound to refluxing setup I've never used Soxhlet apparatus before and I have troubles understanding how to properly perform the following step from my protocol:


  To a gently refluxing suspension of 1 g Lithium aluminium hydride in 100 mL of diethyl ether, there was added 1.2 g of compound as a saturated diethyl ether solution with use of a Soxhlet extraction condenser which is modified allowing the continuous return of condensed solvent (through the thimble). After the addition was complete, the refluxing conditions were maintained."


Soo... How do I do it? I run RBF with condenser on top until reflux stabilizes and then I open it, add Soxhlet with compound and continue refluxing or I set up everything cold (RBF with ether + Soxlet with compound in ether + condenser) and then start refluxing?

Also - I'm not quite sure if I understand the thimble modification - can anyone shed some light on it for me?
In my opinion the intention is to have a very slow addition of the reagent to the hydride. The compound is dissolved in ether, so a Soxhlet is of no use since it is for solids. 

What they are possibly referring to is a liquid-liquid extraction apparatus, specifically the one for extracting with solvents lighter than water:



The saturated solution of the compound is then placed in the thimble and when reflux starts, the solvent is condensed, falls into the tube and returns to the flask carrying over the compound. Normally the tube goes to the very bottom of the thimble. In fact, usually it is a loose tube with a wide opening on the top. How to know that the addition is complete is another story. If the compound is not colored, it will not be easy without opening the system.  In any case, maintaining reflux for a long time will ensure that everything goes into the flask. 

I suppose that for some reason it is difficult to perform a slow addition through a funnel in this case. It would be, however, better to use a syringe pump but not everybody has one of those.