What are the main differences between first pass SPD parameters and second pass?

Ok, maybe my searching skills are lacking but after looking on both Google and on here I couldn’t find any detailed SOPs on a second SPD run.

If my searching wasn’t good enough please kindly send me in the right direction.

My guess would be that the following changes would be appropriate for a second pass:

-Faster ramping up to heads fraction-there shouldn’t be any volatiles
-Removal of one of the receiving flasks-same reason as above
-A hot condenser would probably be a good idea (probably for first run too)
-An additive in the BF could be a good idea here too

Anything I’m missing here?


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If you put something in the BF you’re going to have slower ramp up speed then if theres nothing in there.

Most absorbants produce azulene which must be purged before going into main body.

I call this smurfs blood.

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You ever seen the inside of a smurf?


Search results for 'second pass parameters' - Future4200 actually has useful information.

the majority of hits are to WFE, but if you read between the lines, you should gain some insight into second pass SPD.

ideally you would see deeper vac, and lower distillation temps.