Sciencemadness Discussion Board

Strange separation of layers

Housane - 1-1-2020 at 01:29

Hi when I extracted indigo using an asorbic acid and sodium hydroxide reducing bath and then I acidified it to drop out the indigo and on filtering 2 layers formed the top layer was yellow and neutral but the bottom layer was dark orange and strongly basic. Any idea what the two layers are and why they formed. Indigo was caught in the filter.



[Edited on 1-1-2020 by Housane]

RedDwarf - 1-1-2020 at 07:57

What were you extracting the indigo from? What else might have been present in the raw materials?

walruslover69 - 1-1-2020 at 08:01

are you saying you did a purely aqueous extraction and ended up with 2 separate layers? No organic solvent? Alittle more information regarding the specifics of the procedure would help.

Housane - 1-1-2020 at 10:33

Yeah only solvents were water, sodium hydroxide and asorbic acid then heated with a piece of denim in it and upon acic anaddition it was stirred and filtered to recover indigo and then the 2layers formed

IMG_20200101_090400.jpg - 4.1MB

[Edited on 1-1-2020 by Housane]

IMG_20200101_090421.jpg - 4.2MB

Images of layers

[Edited on 1-1-2020 by Housane]

RedDwarf - 2-1-2020 at 02:17

My only thoughts are that either it's a decomposition product of some polymer fiber in the denim (eg elastane), or of the fiber coatings ( for example magnesium stearate is used on some fibers to prevent sticking).

Housane - 2-1-2020 at 03:19

Ok would the water layer be the top or bottom one, sorry I am new to organic chemistry

Tsjerk - 2-1-2020 at 04:06

How did you make sure there was no more ascorbic acid present?

Shouldn't both layers be at least neutral to acidic? If not you wouldn't have any indigo precipitating. Are you sure you don't still have ascorbic acid in there, keeping the indigo reduced, which then turns blue on your pH-paper after enough oxygen exposure?

In that case I think the layer that turns your pH-paper red is the organic layer. You can always check which is which by putting in a drop of water, if it sinks the top layer is the organic. If it mixes, the top layer is the water layer.

That, or you didn't add enough acid to get the hydroxide neutralized. In that case I still wonder how much ascorbic acid is still in there, as your pH-paper looks like there is a bunch of indigo in that water layer.

[Edited on 2-1-2020 by Tsjerk]

Housane - 2-1-2020 at 07:12

I will try that when I am back at the lab, here is a picture of the collected indigo.

IMG_20200101_090654.jpg - 3.7MB