AMAR NATH PURI AND VED RATTAN 139
Curiously enough this most fundamental and vital point, i.e. the stability of the dye, had been
ignored hitherto. It would be clear to any body that no dye would be recommended for colouring
artificial ghee if it could be easily removed by simple treatments requiring no technical skill. The
removal of colouring matter from oils and fats is well known to chemists and the decolourizing of
natural fats is. being carried out in hundreds of places with methods based on the well-established
bleaching properties of activated charcoal, light and heat; and there appeared no reason for the belief
that any colouring matter added to artificial ghee would resist such treatments.
The following list of oil-soluble dyes practically exhaust the entire range of possible colours
that could be used for colouring artificial ghee irrespective of their physiological effects.
Natural dyes
1. Ralanjot—Onosma echoides Linn
.
.
.
.
.
.
.
2. urmeric—Curcuma longa Linn . . . . . . .
3. kashmiri mirch . . . . . . . . . . .
4. Spinach—Spinacia obracea Linn . . . . . . .
5. Kamala—Mellotus philippinusis Muel. . . . . . .
6. Annato—Bixa orellan Linn. . . . . . .
7. Saffron— Corous sativus Linn.
.
.
.
.
.
.
8. Carthamus tinctorius Linn.
.
.
.
.
.
.
Synthetic dyes
1. Oil Orange E
2. Oil Orange AS
3. Oil Orange Saco
4. Oil Green BY
5. Oil Green 33707
6. Oil Green Saco
7. Oil Red Saco
8. Oil Yellow GG
9. Butter Yellow
10. Butter colour
11. Sudan—I, III and G
12. Aniline Yellow
13. Yellow AB
14. Yellow OB
15. Oil Orange SS
16. Oil Red XO
17. Waxoline Victoria blue
18. Waxoline Green B
19. Waxoline Orange YS
20. Waxoline Red BNS
Items Nos. 6, 7, and 8 of the natural dyestuffs are not commercially available in large amounts
and over and above this they are known to be very much less stable than other natural dyes.
The following methods of bleaching the coloured ghee were used :
1. Exposure to sunlight
Two millimeter thin layers were exposed to light and tintometric readings recorded at regular
intervals. The maximum bleaching that could be obtained was noted and the time taken for the
bleaching also given.
2. Treatment with absorbents
Different amounts of activated charcoal, ordinary charcoal and Fuller's earth, were used to
absorb the colour. The maximum absorption by these absorbents is mentioned and the amounts
of absorbents used per 100 c.c. of coloured ghee are given in brackets. Temperature was kept
constant at 50°C.
3. Effect of heat
Samples coloured with different dyes were heated to 150-300ºC. Maximum bleaching is mentioned
against time and the temperature is also recorded in brackets.
4. Effect of aeration
Simple aeration was carrried out at 50°C. and the bleaching, if any, is mentioned against time.
5. Effect of alkaline and acidic washing
The samples were washed with equal volumes of hot solutions of H 2 SO 4 (5 per cent), HCl(5 per
cent) and Na 2 CO 3 (2 per cent). The amount of colour removable in the watery fraction is removed
and the tintometric reading taken in the centrifuged ghee left behind.
All the measurements of the intensity of colour were made by tintometric method using Lovibond
Tintometer (BDH Pattern). The original concentration of the dye in every case was taken as cent
per cent standard and the loss in the intensity of colour is expressed in percentage of the original
intensity of the dye solution. Tables I and II summarize the results with all the natural dyes.
D