I live in New Zealand and I cannot get a specific welding flux any more. The components are 20% Methanol 25% Acetone and 55% Trimethyl Borate.
I am going round in circles trying to find out how to make Trimethyl Borate. Each web page I get to, I get a different formula.
I have managed to find Borax and I have the other 2 items but I'm not sure how to continue. There are a few web posting about making green flames with
Borax and this is correct, as when I used the original flux, it did burn with a green colour.
Any suggestions or pointers as to where to go from here. I would like to make about 2-3 litres. UC235 - 4-7-2015 at 09:04
Was this flux painted on to the part or injected into the gas line? I suspect the latter, but if the former, you could simply paint a solution of
boric acid in methanol onto the part. Producing trimethyl borate is not particularly easy without lab equipment and a whole liter of it would take
quite a bit of work even with it.Magpie - 4-7-2015 at 09:14
Here's my procedure for making pure methyl borate. If you are not concerned with the methanol impurity you can skip most of the workup steps.
>> Was this flux painted on to the part or injected into the gas line?
The process used for Jetflux is to bubble the acetylene through the liquid.
However, having the option to paint on the flux would be an advantage. Often when brazing around a tube, once you get back to the start there is
oxidation in the tubes. Possibly painting on the flux before starting to heat the tubes may help with this.
Brazing with Jetflux is really far superior to dipping or coated rods. marsheng - 4-7-2015 at 17:46
It was a long time ago I did chemistry (30 + years) so I'm quite rusty.
As for the web, anyone can post and so anyone's opinion will come up, hence I'm here at this forum to hopefully find out the right answers.
To clear a few things up
From what I have read Boric acid is a white salt at room temperature.
To create Boric acid from Borax
Take 25 ml of hydrochloric acid and dilute it with 75 ml of water. Next take 6 - 7 gms of borax and dissolve it in boiling water. Now add equal amount
of hydrochloric acid. Crystals of boric acid will start forming. They are completely insoluble in cold water. After about half an hour, filter it and
you have the boric acid crystals. Wash the beaker only with cold water to prevent loss of any boric acid.
The link from Magpie is to make Methyl Borate CH3BO3. I need to make Trimethyl Borate C3H9BO3.
Is there a possibly to make Trimethyl Borate directly from Borax ? Magpie - 4-7-2015 at 18:45
Is monomethyl borate actually stable?marsheng - 5-7-2015 at 19:40
Thanks for the reply. Still confused as they have different compositions.
Could it be that Methyl Borate is the powder form and Trimethyl Borate is the same just dissolved in Methanol ?
Looking at the parts
2 x Methanol CH3OH + Methyl Borate CH3BO3 may well be
Trimethyl Borate C3H9BO3. (However 2 too many O's)
Thanks Wallace
DraconicAcid - 5-7-2015 at 19:52
Methyl borate and trimethyl borate are the same things, just like sodium phosphate and trisodium phosphate are the same things.
Boric acid is H3BO3. If you replace the acidic hydrogens with methyl groups, you get (tri)methylborate. It is a liquid at room temperature, with an
unpleasant smell, and it burns with a lovely green flame.Magpie - 5-7-2015 at 19:54
I believe that methyl borate is the archaic name. In the old references listed at the bottom of my procedure it is called by that name.
Borate (BO3---) has a valence of three. One methyl doesn't make any sense - it's just an old name that is not used anymore. marsheng - 5-7-2015 at 20:08
Sorry I got the previous post wrong. Is this correct then ?
2 x Methanol CH3OH + Boric Acid CH3BO3 makes
Trimethyl Borate C3H9BO3.
Thanks WallaceMagpie - 5-7-2015 at 20:21
Did you look at my procedure? I give the reaction there.marsheng - 5-7-2015 at 21:21
Thanks for all the info. I think I have finally got it all together. Youtube made it look so easy, but it is not so.
I need to buy a few more things to get this all up and running now. Sounds like a fun project. I really need to only make 250 mm at a time.
The alternative to just buy Trimethyl Borate but even that was confusing as some suppliers sold it by the litre and others by the KG. However no-one
stocks this in NZ and the delivery time is 4 +weeks and around $200 per litre. Hickory - 6-7-2015 at 15:42
I have successfully made MeO)3B•MeOH azeotrope by baking borax dry and heating with methanol (and glycerine, soap, and lye, but probably they're
optional - waste glycerine layer from biodiesel).
Monomethly borate exists, as the cyclic trimer when dry, which is why methyl borate as a synonym for trimethyl borate is frowned on now.
