Sciencemadness Discussion Board

Trimethyl borate

DalisAndy - 13-10-2015 at 12:03

Does anyone know if Trimethyl borate is soluble in ethanol? I can't find any info on its solubility except in water. Reason why I'm asking is cause I was going to use denatured alcohol for my methanol source.

Detonationology - 13-10-2015 at 12:28

If I remember correctly, only lower alcohols (methanol and ethanol) are capable of reacting with boric acid to form either trimethyl or triethyl borate respectively.

Detonationology - 13-10-2015 at 12:35

I just mixed some boric acid and isopropyl alcohol together with a drop of H2SO4. The product burned with a typical bluish/orange flame, not the characteristic green flame. Heet gas line antifreeze (methanol) has the best results, but I believe that the less used denatured ethanol would provide similar results to those of trimethyl borate.

DalisAndy - 13-10-2015 at 12:58

But would trimethyl borate dissolve in ethonal?

Bert - 13-10-2015 at 13:01

The excess carbon in ethanol disturbs the green flame- Use methanol for the best results with any alcohol flame colorant except Sodium.

Detonationology - 13-10-2015 at 13:10

Quote: Originally posted by Bert  
Use methanol for the best results with any alcohol flame colorant except Sodium.

Should ethanol be used if a sodium compound is being used? What about the case of using sodium tetraborate as the source of boron?

Bert - 13-10-2015 at 13:15


https://books.google.com/books?id=TjhHAQAAMAAJ&pg=PA323&...

[Edited on 13-10-2015 by Bert]

UC235 - 13-10-2015 at 13:37

Yes, trimethyl borate is probably miscible with ethanol. Transesterification will almost surely occur to mixed methy, ethyl borates but this shouldn't change the flame color since it is atomic boron produced in the flame that emits green.

Methanol burns with a clean blue flame while alcohols like ethanol and isopropanol require a lot more oxygen to burn completely. The resulting flames are usually partly or completely yellow due to emission from carbon radicals and soot particles.

Borax is useless as a source of boron for flame coloring since the yellow sodium emission band is extremely intense and will cover most other flame test colors completely.

Detonationology - 13-10-2015 at 13:47

Quote: Originally posted by UC235  
Borax is useless as a source of boron for flame coloring since the yellow sodium emission band is extremely intense and will cover most other flame test colors completely.

In my earlier years of chemistry, I had no idea what would happen if I mixed some of my methanol camp stove fuel with borax. I was quite surprised to see a beautiful GREEN flame. Try it. I have some pictures of it, if I could figure out how to post them on here.

[Edited on 10-13-2015 by Detonationology]

Detonationology - 14-10-2015 at 20:23

Here is crude trimethyl borate (I'm assuming) made from methanol and sodium tetraborate decahydrate. The sodium does not exhibit much of a yellow/orange tone at all.

IMG_0048.jpg - 394kBIMG_0062.jpg - 85kB