Org Prep Daily

May 24, 2013

Oil pump desanguination – brilliant!

Filed under: procedures — milkshake @ 3:38 pm

I just had the fastest and most enjoyable pump oil change of my career, thanks to a colleague. We use large Welsh DuoSeal belt-driven pumps installed in metal cabinets under the hoods and these beasts are rugged, dependable – but so heavy: They take over 3 liters of oil to fill and the whole damned thing weights about 50 kilos. The oil drain valve is inconveniently located right near the bottom so the pump cannot be easily drained inside the cabinet. The normal oil change procedure requires disconnecting the vacuum hose and dragging the pump out. I would prop the pump on an empty solvent barrel, put oil collection bucket beneath the drain valve and keep draining, tilting, flushing, draining, filling, cursing. Lifting the pump requires two pairs of hands, the oil drips everywhere, and given the large and awkward shape of the (very heavy) re-filled pump that has to be finally coaxed back in and over the cabinet lip, the vacuum hose reattached and the inadvertent vacuum leaks fixed, it is a pretty unpopular job – a job that keeps getting postponed for as long as is possible, while pumps are left sloshing with tired crud that has the look and smell of burnt molasses. But not much longer!

Prodded by his injured back and by desperation, my colleague conceived a brilliant apparatus –  he took a large (4L) Erlenmeyer filtration flask closed with a stopper with a tube through it. To the tube he attached a cheap vinyl transparent tubing (like you would use for water in reflux condensers) and connected it to the oil drain valve at the bottom of the pump so that he can aspirate the spent oil by vacuum. Turns out, if the oil is warm (from a pump that has been run, so it is less viscous), it can by sucked out through the drain valve into the Erlenmeyer filtration flask under house vacuum in few minutes. After one fill with flushing oil, 2 min pump run and another suction-assisted drain and final re-fill, the entire oil changing operation can be completed in less than 15 minutes. No mess, no need to take the pump out, no need to disconnect the vacuum hose from the pump.

Our biologists of course claimed credit for the pump oil change idea, for having used this kind of setup previously when sucking off liquor from cells in multi-well plates. But I am afraid the true origin of this oil change breakthrough is rather more disturbing. You see, my colleague is leaving for medical school in few weeks and in preparation, he has already taken the anatomy labs. As I was sucking out gallon of alarmingly dark rotten muck from my pump with his gadget, he calmly observed that the really good, top-of-the-line embalming machines can aspirate blood while at the same time pumping formaldehyde solution back into the empty veins: The happy operator just needs to correctly insert the inlet and outlet tubes into the still body, turn on the flush routine and wait until the aspirate finally starts coming out clear…


  1. Amazing.

    Comment by Chemjobber — May 24, 2013 @ 5:33 pm

  2. If I remember, those old pumps have an outlet near the top. Loosing plugging the outlet with a thumb will pressurize the oil reservoir and, with the drain plug open, drives out the oil. Same result, but w/o the house vac.

    Comment by damifiknow — May 25, 2013 @ 10:47 am

  3. This blog entry was brought to you by Six Feet Under (a pile of JACS to be read…)

    Comment by ElVince — May 27, 2013 @ 7:41 pm

  4. Isn’t your setup a siphon then? I’m not quite sure I understood it fully.

    Comment by PGMChem — May 28, 2013 @ 6:14 am

    • its just an improvised trap-reservoir into which you suck the spent oil using house vacuum – just like a filtration setup where you replace Buchner funnel with only a tubing. Look up a picture of “embalming machine” to get an idea

      Comment by milkshake — May 29, 2013 @ 10:37 am

  5. I’d be a bit wary of using Erlenmeyers of that size to pull very viscous liquids unless they’re the polymer-coated safety variety. The stresses in large flasks under vacuum are more severe than small flasks, especially across flat areas like the bottoms of Erlenmeyer flasks. In addition to containing fragments, the polymer coating prevents the glass from getting scratches and dings that serve as crack-formation nidi. It should be no big deal if the oil is hot enough, though.

    Comment by a. nonymaus — May 30, 2013 @ 10:33 am

  6. I used to use a similar method to remove solvent from full 20L containers to avoid lifting and pouring.

    Comment by MasterChief — June 10, 2013 @ 10:49 am

  7. Good luck washing the flask afterwards.

    Comment by chirality — June 14, 2013 @ 2:54 am

    • but we don’t – we keep it befouled. With several oil pumps running permanently, someone is going to use it again in a week or two.

      Comment by milkshake — June 14, 2013 @ 10:56 am

  8. I bought one of these units designed to extract the oil from small engines:

    Works great.

    Comment by RB Woodweird — July 3, 2013 @ 11:13 pm

  9. Hey Milkshake,
    Can I tap your brains? We use columns with fritted glas just above the tap for flash chromatography. They all work fine except the 1 cm diameter variety. After a while they start to clog and a column will take for ages. Reverse rinsing the column with water does not push back the silica (I guess it must be clogged by silica gel…). Any possible fixes? Should I just put the thing into iPrOH/KOH for a day to soak the fritted glass in base?
    Thanks for your help,

    Comment by Young Padawan — July 8, 2013 @ 7:40 am

    • I have not done this myself but I think diluted aqueous NaOH would be the way to go, I would start for a short time with sonication on ultrasound bath, to see if it flows again. You can always leave it longer if you need to but I would start carefully because once you dissolve your frit too much it might start crumbling under pressure

      Comment by milkshake — July 8, 2013 @ 10:06 am

      • Cheers Milkshake, I’ll try it out. Let’s see if this does any good….

        Comment by Young Padawan — July 10, 2013 @ 2:43 am

        • This problem just came to my mind again. Using some 10 % aqueous NaOH did not really fix the problem. I pushed through some, to soak the frit down to the valve and then put it in the sonicator for a couple of hours. Result: Nothing. Thanks for the idea though…

          Comment by Young Padawan — August 16, 2013 @ 9:51 am

  10. I witnessed an oil-change similar to this on my old Audi 80. Rather than loosening and removing the (incredibly tight) sump plug on the bottom of the engine the mechanic merely inserted a flexible tube through the oil filler and sucked out the spent oil. Much quicker and easier than the traditional method.

    Comment by Nick K — July 26, 2013 @ 8:12 am

  11. I also used the same trick with a adaptor piece to cleanly transfer larger volumes with organic solvent into my separating funnel (5L). No pouring, possible splashing, or fumes spreading around.
    With a drying tube between household vacuum and tube with needle, this also works wonders for cannulating larger volumes…

    Comment by tora — August 12, 2013 @ 4:42 am

  12. Hi Milkshake. I would love some practical advice if you have any. We are making spiroepoxides via epoxidation of 1,1-disubstituted alkenes with DMDO to give a 1:1 mixture of diastereomers. This is not a big deal, in principle, but we have to separate the isomers via chromatography. The problem is we can’t find any tlc stain to visualize these things, making the pooling of chromatography fractions a bit of a guessing game. The compounds are multifunctional, with the oxirane ring, an alkyl carbamate, a benzyl triazole all decorating the molecule. I am quite sure this is a problem with a solution, but we’ve tried UV, iodine, CAM, PAA, KMnO4, ninhydrin, PMA. Do you, or anyone else, have any other suggestions? We’re getting desperate. Many thanks. BTW, we have tried reagent control (Shi) to improve the diastereoselectivity with no success.

    Comment by PotStirrer — August 12, 2013 @ 8:24 am

    • that sounds like a quite annoying problem. I could think of two more stains to try – anisaldehyde and Dragendorf. Both recipes are here:

      The bake with anisaldehyde solution containing sulfuric acid should turn your spiroepoxides into keto compounds by pinacol rearrangement, and the produced keto compounds should produce some colored condensation products with anisaldehyde. There is also vaniline stain which uses vaniline in place of anisaldehyde, the results are quite similar to anisaldehyde but the spot color can be little different so it is also worth trying.

      The reason why i think you should try Dragendorf is that sometimes it is very sensitive to lipohilic compounds that have some basic groups, typically alkaloids. But I have seen compounds that are almost nonbasic – triaryl phosphines, crowns, polyethylene glycol – that stain with Dragendorf very well (just dip without heating, the color development is instant) so I think it has some chance with your benzyltriazole.

      [By the way, you don’t have to post off topic on the latest post to get my attention, new comments even under old posts immediately show on my admin bar]

      Comment by milkshake — August 12, 2013 @ 12:45 pm

      • Thanks for the quick reply. We’ve tried anisaldehyde…PAA is my abbreviation for it. We also tried vanillin. I forgot to mention that. So, Dragendorf it is. I still have trouble believing that they don’t stain well. They do, to some degree, at high concentrations. It’s the dilute chromatography fractions that pose the real problem.

        Comment by PotStirrer — August 13, 2013 @ 3:50 am

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