Wiki page for members bio oxidisation tests

[countrypaul]

Julian

It does not surprise me that the copper one is much closer to the normal bio. Copper will form a coating as I explained and that will limit the amount of bio that can complex with it. Anything that does dissolve in the bio is likely to supress its freezing point (well gel point in this case) think of how salt water freezes at a lower temp than fresh, or bio with petrol in gels at a lower temp than fresh (which I had a better example for bio!)

Another issue that is dfficult to measure like this is the effect of any bugs landing on the samples. In the case of simple Bio, these bugs can probably grow slowly, in the case of copper being present they would probably be unable to grow, with iron present they are quite likely to grow. I have no idea whether any of the samples will have a significant amount of biological activity or not, but just a theory.

How do the bio and copper samples compare with bio that has been kept free of oxygen and light?

[Jamesrl]

See, an' you thought I was talking out me rear end when I mentioned bacteria.

[Julian]

I didn't keep a sample from the same batch, but my storage tank is in the same place, is HDPE so cuts out a large portion of ambient light and is sealed save for a small vent and the bio in that is fine, but that's not really a fair comparison.

There's no visible signs of biological activity but I guess that doesn't mean it's not there.

[dgs]

If the bio really does oxidise, I would have thought that the colour would deepen. With my samples other than the one with the steel (where the bio is rusty) the only thing that has happened is that they are now really thick ie polymerised.

They have been on the bench in the bio room in petri dishes so partially open to air and have been subjected to between -5 and around +28degs.

There are reports on infopop of people using 2 year oil bio without problems so I don't think we need to worry.

[Jamesrl]

There's no visible signs of biological activity.

I'm not surprised you can't see any bugs, they're only about 4.5u long.

Unless of course you've been to Specsavers.

[Tony]

Yesterday I opened an old 25l drum with a thin layer of biodiesel on the bottom.  It was like treacle, and had the bitter smell I associate with oxidised biodiesel.  Clearly not much air exposure is required for this (whatever "this" is) to happen.  It was still clear light yellow, however, not red/orange in colour.

[Twenty4Seven]

The bitter smell (I would call it acidic) is going to be low molecular weight carboxylic acids.... eg formic, acetic

I will post some pics of my samples... the most striking observation is how the steel has reacted. I wonder if some of the brown stuff we find in our fuel filters are in fact iron complexes rather than glyc?

Nick

[Julian]

I get brown gunk in the Disco filter.  The only steel part of the fuel system is the pick-up pipe in the tank, but that has a heavy zinc or similar coating and shows no sign of corrosion.

[dgs]

http://biodiesel.infopop.cc/eve/forums/a/tpc/f/419605551/m/1327038083?r=1327038083#1327038083

[Julian]

Yup, that's similar to what I get in the storage tanks and car filter  ... nothing like that bad though.

[dgs]

I thought Wesleys' last post was interesting re fatty acids with double bonds causing auto-oxidation.

Julian, I was under the impression that you water washed your bio, so your residue can't be anything to do with glycerol.

[Julian]

Yes I do ... 5% glycerin wash, acid wash and two or three water washes all with Frankinpump.

[Tony]

Just had a quick chat with a professor at Southampton Uni and he pointed me in the direction of this:

https://www.metrohm.com/en/products/stability-measurement/rancimat/

Rancimat, as you might guess, measures rancidity - so our theory that the nasty smell from the bottom of old drums is from oxidised biodiesel holds out.

[dgs]

Same company that made my Karl Fischer Water auto titrator (Metrohm KFD 758)