The Chemical Gazette 332, 15.8.1856
By J. Pelouze.
All the fixed oils are not equally proper for the preparation of the dyes known under the names of Turkey-red and Adrianople-red. Those generally used are olive oils, distinguished by the name of emulsive oils (huiles tournantes), from the property which they possess of producing a milky emulsion with a weak alkaline solution. To distinguish them, the manufacturers let fall 1 or 2 drops of the oil into a test-glass partly filled with a solution of caustic soda marking 1½ to 2 degrees, and judge of the value of the oil by the greater or less opacity of the drops of oil. The oils proper for the manufacture of Turkey-red being expensive, it has been endeavoured to replace them by cheaper oils, mixed with yolk of egg, treated with nitric acid, &c., but without success, as the manufacture of Turkey-red still consumes great quantities of natural emulsive oils.
* Chem. Gas, No. 301, p. 161.The author formerly showed* that if crushed oleaginous seeds were left to themselves, the neutral fatty bodies contained in them were chaged into acids, and announced that these partially acidified oils would then shortly be applied in the manufacture of Turkey-red. He has ascertained that the oils used for that purpose were mixtures of neutral and acid fatty bodies; and by treating them with alcohol, found that they yielded portions of oleic and margaric acids varying from 5 to 15 per cent. The acids may also be extracted from the oils by heating them for a few minutes with an alkali. Ordinary olive oil contains no fatty acids, or only an insignificant quantity of them.
The author's observations on the spontaneous saponification of fatty bodies easily explain the difference in the composition of these oils. The pure oils are obtained by the simple division and immediate pressule of the olives, whilst the treatment of the cakes and other residues, and the fermentation of the olives, cause the acidification of the oil, and render it emulsive (tournante).
For some years M.M. Boniface of Rouen have prepared an artificial oil of this kind; and the author, on examining it, found it to contain considerable portions of oleic and margaric acids, but the process by which it is prepared is not known. However, it appears that the only difference between the two categories of commercial oils—those fitted for dyeing are mixed with fatty acids, whilst the others are free from them. M. Chevreul, also, more than twenty years ago, extracted two oily matters from Turkey-red stuffs; one of these was neutral to litmus, whilst the other reddened it, and was composed of oleic and margaric acids.
The author states that olive-oil has been almost exclusively employed in dyeing Turkey-red, because olives give rise to the reaction which produces the fatty acids more readily than the oleaginous seeds, and that it will be easy to substitute for it cheaper oils, such as poppy-oil, oil of sesame, colza-oil, palm-oil, &c. It will be sufficient to crush the seeds or kernels, and leave them for a short time before extracting the oil. A still more simple means consists in adding to the oils a few hundredths of their weight of the oleic and margaric acids furnished by the manufacturers of stearine candles. This last method has succeeded with M. Steiner of Manchester, and M. Pelouze also communicates a letter from MM. Henry of Barle-Duc, containing some useful information on the substitution of artificially acidified oils for those which are naturally acid, and exhibited to the Academy of Sciences specimens of cotton-dyed Turkey-red with both the natural and artificial oils, and between which there was no perceptible difference.
He adds, that it is very probable that the treatment of certain oils, especially colza-oil, with a little sulphuric acid, would give rise to mixtures of neutral oils and fatty acids, which when well washed would be fit for the manufacture of Turkey-red.
MM. Henry state that the quantity of oleic acid required to give the necessary properties to the oil varies according to the nature of the latter from 5 to 15 per cent, and they have even produced the effect with 2 per cent. The oils require to be purified to a certain extent. The cotton-dyed (10 kilogrms. of thread) gave a good tint, proportioned to the madder employed; the oil used was 3 kilogrms. of purified colza-oil with 60 grms. of oleic acid, or only 2 per cent. They are convinced that it will succeed on the large scale.
— Comptes Rendus, June 23, 1856, p. 1196.
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