I'm planning to start experimenting with composting glycerine, but I want to neutralise the KOH first. I've tried sulphuric acid, that made a gluggy mess, and also hydrochloric acid which was a little better. But I really want to try using Phosphoric acid as this will produce potassium phosphate which I understand to be a fertiliser.

Anybody know where I can buy industrial grade phosphoric acid in reasonable quantities (& price), maybe 5-20L? I know that Rust Converter contains phosphoric acid but this will be a very expensive way to buy it in such small amounts.

Gee I'm not surprised no one has touched this. My initial reaction (with my very limited experience ) is that you should be careful. Potassium is know for going BOOM when mixed in the right quantities with other stuff. Dunno about actually neutralising glycerine from KOH but I thought all ya need to do was distill the methanol off and it was safe for composting.

Also be alert but not alarmed (potassium phosphate?!? )... you'll have the feds knocking on your door

Isn't it Nitrates that are now controlled as Anti-Al Quaeda substances?

Sorry Joe, I didn't mean to alarm you, Let me try to put your mind at rest. Regarding the BOOM issue, I think you're confusing the pure metal potassium (and sodium) with the compound potassium hydroxide (KOH). These pure metals react violently with water. Or maybe your thinking of potassium nitrate (saltpeter) which is a component used in gun powder and fireworks.

Yes, you're right the glycerine could be composted directly after methanol recovery. But remember it is still highly caustic, most of the KOH or NaOH you put in the original reaction remains in the glycerine (except for a small amount which converted into soap). This is the function of a catalyst, to facilitate a reaction, but not take part in it.

I could neutralise the KOH in the glycerine with more readily available acids such as vinegar, citric acid or pool acid (hydrochloric) but it seems such a waste of the valuable potential fertilizer potassium phosphate. The acid-base reaction of KOH + H3PO4 (phosphoric acid) seems an elegant solution.
Maybe Neutral's out there watching and may like to comment.

Here's the result of a little bit of googling from:
http://scifun.chem.wisc.edu/chemweek/H3PO4/H3PO4.html

"Phosphoric acid, H3PO4. Most production (about 80%) is used in the production of agricultural fertilizers, with the remainder being used for detergent additives (about 10%), cleaners, insecticide production, and cattle feed additives.
Phosphoric acid is used primarily in the manufacture of fertilizers, detergents, and pharmaceuticals. In the steel industry, it is used to clean and rust-proof the product. It is also used as a flavoring agent in carbonated beverages (read the ingredients list on a can of Coca-Cola), beer, jams and jellies, and cheeses. In foods, phosphoric acid provides a tart, acidic flavor.
In the manufacture of detergents, phosphoric acid is used to produce water softeners.
Most phosphoric acid is used in the production of fertilizers. Phosphorus is one of the elements essential for plant growth. Organic phosphates are the compounds which provide the energy for most of the chemical reactions that occur in living cells. Therefore, enriching soils with phosphate fertilizers enhances plant growth".

I might add this is not my idea, there's a page on the (dare I mention it) 'Journey to Forever' website describing how to do it:
http://journeytoforever.org/biodiesel_glycsep.html

It may be the case that's it's uneconomic to use phosphoric acid, that's why I was asking if anyone knew where to buy the industrial grade stuff. I know I can buy it from lab chemical suppliers but they sell the pure stuff at incredible prices. Hope that helps explain the reasoning behind my request.

HI wizzo,
You can get phosphoric acid at $400/MT. And the fertilizer you make sells for up to $2500/MT.

Just to set your minds at rest Phosphoric acid is quite safe to use if your careful ie use gloves, but be aware that it is used in drug labs so purchase may attract attention.

It works very well, if I had a digital camera I would show you just how well. It seperates nicely into three layers, a salt (potassium phosphate - fertiliser) acidified glycerine layer and a FFA layer.

I will try and borrow a camera to post piccies.

Matt

Thanks Matt and Liquidgold that's great, but where do you get the stuff?

Matt, like this? (picture copied from JTF website)

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Any industrial cleaning / chemical house. I know of one here in Brisbane but I am sure there will be one on Sydney.

For an experiment use HCl (hydrochloric acid), you will end up with Potassium Chloride, a salt. The Glycerine layer will be acidified with HCL and the FFA will seperate easily.

Get a litre of you byproduct and add upto or exceeding 100ml of HCL, be careful with it as it fumes badly, add a bit and stir and watch it will happen before your eyes.

Matt

Bingo! Thanks again Matt, I've found some..... and I'm embarrassed to say it's the same place I buy my KOH - Kleenco Just didn't think to ask as they sell mostly pool chemicals. $4/kg, bring your own container.

Yeah like I said limited experience. Good to see you know what your talking about. Its clear I dont. :-)

Joe