Yes I realize that this is a very old thread, but I am sure there are new generations of little kids getting all excited about cannabis, googling the hell out of it, and falling asleep to dreams of the most ultra-potent honey oil known to man.


Let me first give you the, unfortunately negative, "death of your dreams" comment that all forum posters hear:

its never gonna happen, its a waste of time and money, and its too difficult if you are asking questions on a forum.


with that said, I will answer OP's question.

OP wants to do "Flash" chromatography, which is a bench-top procedure that is used all the god damn time in chemistry labs of all shapes and sizes all over the world. easily the most common method of chromatographic separation.

it requires a relatively large amount of solvent. it is also very sensitive to the amount of material you are trying to separate. 10 grams is about as much as you could ever separate using flash chromatography.

most people separate about 500 mg to 1 gram at a time (maximum). They do make columns designed for larger loading, but they are hilariously large. 10 gram column loading will require a column with about a 10" diameter (they call them "horse dicks" or "donkey dicks" because they are soo big). these are usually also at least 2 feet in the length of the main column section.

you need somewhere in the neighborhood of 0.5 to 1 mL of dry silica per miligram of material to be purified... this is a very general rule of thumb, and some labs use a different metric. it depends on what and how much you are purifying. keep in mind, "donkey dick" columns can hold about 20 liters (pi*(12 cm)^2*50 cm volume ~ 22 liters).

when you buy silica, as a researcher, you buy big fucking barrels. literally. big barrel. like 2-3 feet tall, 3 feet in diameter. big gigantic plastic barrels full of the stuff.

most O-chem labs have MANY MANY of these big barrels. so that gives you an idea of how much and how quickly you use this stuff.

basically, if you are going to purify 500 miligrams, you would use 250 to 500 mL of dry silica. if you are going to purify 10 grams, you would want to use around 10 liters of the stuff.

you would then pour hexane into the dry silica to make a "gel" or "slurry."

you put a cotton plug at the spout of the column (the "bottom" where stuff comes out), pour a little bit of sand or sodium sulfate on top... then pour the slurry on top of that.

you then "pack" the column by agitating it, causing any voids or bubbles to collapse, so that the density of the silica slurry is more or less even throughout the entire column length.

people usually achieve this by banging on the column with the palm of their hand (we used to tap on it with our cork-stands). you do this for a few minutes, making sure to get it as even as possible on all sides and parts of the column length.

you then pour sand/sodium sulfate on the top of the slurry to "protect" its surface


now, at this point, you should still have a little bit of solvent visible above the layer of the silica/sand, because you packed it in and so it condensed a little bit. You should push this layer of solvent down to just barely above the silica/sand (the top of the column packing) with the air pressure. do not push it further.

you must obviously have the stop-cock open to allow the solvent to run through, but immediately turn it off as soon as the solvent has been pushed to the correct level.

you then dissolve your mixture (BHO) in the solvent system you will begin with (say, hexane:ethylacetate 75:25 or something).

you then put the air-pressure on to push the visible solvent so that it is JUST BARELY above the surface of the sand/sodium sulfate layer (DO NOT push it all the way into the layer, this "dries" the column and ruins everything).

again, you must open it and close it during this procedure

you then add the first batch of your solvent system to the bulb (most flash columns have a "bulb" at the top, so that you can add enough solvent to keep it going for a while).


you then begin pushing it through and collecting fractions.

Periodically you will have to add more solvent.



so if you do the math, purifying 10 grams of material with flash chromatography is expensive as hell. In solvent and silica alone, I am thinking something like $500 to $1000 for 1 single extraction.

the column would probably cost around $200. and you are going to have a hell of a time evaporating the LITERAL gallons of eluted solvent without a rotovap (which cost around $5000 if you include everything, from the rotating section, to the condenser, to the collection flask, to the vacuum pump)




Chromatography is always expensive and time consuming. When they make drugs on the large scale, they usually try to avoid it, because it is so expensive to use chromatography. Even the most ridiculously huge factory-sized columns can only purify 1-100 kilgrams at time...

any chemical produced on the thousands or hundreds of thousands of kilograms per year scale DOES NOT USE chromatography at any point in its synthesis.


purifying 1 kilogram of material requires a 1-2 foot diameter, 3-4 foot long column at about 3500 PSI or more. its the type of thing that requires a mechanical engineer to design.