Indigotin

 

Indigotin

Chemical formula	C16H10N2O2
OTP appearance	blue solid
Molar Mass(g/mol)	262.27
Density(g/cc)	1.199
Melting Point(°C)	392
Boiling Point(°C)	decomp
Solubility in water(g/L)	.000990
NFPA 704	1 1 0

Uses

Justification Questioned

Other

• Dyestuff, pigment
• Precursor to aniline

Natural occurrence

• Occurs naturally in several plants:
  • Indigofera Tinctora [legume, nitrogen fixer, high yield; long hot humid season]
  • Persicaria Tinctorum (japanese indigo) [2 harvests per year]
  • Woad (25% yield of indigo)

Production

Once source estimates 404 hectares produces 7t of indigotin per year

Extraction

Bellos

According to a youtube video

1. Gather all above-ground plant matter
2. Place in large container
3. Hold plants under water with weights
4. Add enough water to cover plants
5. Warm water to 25-30°C
6. Cover container with tarp
7. Wait for the water to become yellow/brown
8. Wait for the water to become blue/green
9. Remove plants
10. Repeat
    1. Add calcium oxide
11. Until water turns opaque yellow-brown, and then a clear red/brown
12. Wait until the green/blue indigo pigment has fully settled out of the red/brown water
13. Decant & Filter
14. filtrate is highly alkaline. Neutralize & discard.
15. Prepare saturated water/calcium hydroxide solution
16. Wash residue with solution twice
17. Residue is indigotin

Chanayath

Three different samples : fresh, semi-dried and dried plant materials were taken from the same source. The semi-dried materials were the plants that dried at room temperature (30±2 ºC) for 3 days. The dried materials were those  that dried at room temperature (30 ± 2 ºC) for 7days.
[...]
Plant materials were cut to small pieces, fermented in water at different periods and then added twice in volume of Ca(OH)2  solution (pH~11), blew the air for 15 mins to precipitate indigo. The precipitated indigo was washed twice with Ca(OH)2 solution and centrifuged at 9820xg for 10 mins.
The most effective way to get good yield of indigo paste was done by maceration of small  cut  pieces  of  plant  material  with  water  in  cotton  bag  and  covered  the  container  to reduce unpleasant smell  and it was easy to get rid of waste
[...]
The yields of the indigo dye from the fresh plant materials were highest. The semi-dried and dried plant material gave significantly low yields

Apparently a liquid-liquid extraction was done to refine the "crude paste" to "Indigo dye". In this experiment 3-4g of "Indigo dye" were produced per kg of plant material macerated.

1. Gather freshly picked indigo-bearing plant material
2. Wash material with water
3. Macerate plant material, retaining liquids expressed
4. Combine plant material and liquids with distilled water
5. Filter
6. Discard residue (plants)
7. Add calcium hydroxide until pH is 11.
8. Bubble air through the mixture for 15 minutes
9. Filter
10. Discard filtrate
11. Wash residue twice with saturated solutions of calcium hydroxide
12. Residue is indigotin.