AnnattoCHAPTER XVIII. Colouring Matters of Unknown Constitution.(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

This is derived from the fruit of the Bixa orellana (Linn.), a shrub found native in Central America, and cultivated in Brazil, Guiana, Mexico, the Antilles, and India.

To prepare the dyestuff, the seeds and pulp are removed from the mature fruit, macerated with water, and the mixture is left to ferment. The product is strained through a sieve, and the colouring matter which settles out is collected, partially evaporated by heat, then placed in boxes, and finally dried in the sun.

Annatto comes into the market in the form of cakes, and among the different varieties Cayenne annatto is the most esteemed, and is considered to be the richest in colouring matter. It should contain from 10 to 12 per cent, of the pure dye, and not more than 5 per cent, of ash, whereas the amount of colouring matter in the Bengal product is frequently lower than 6 per cent.

In 1848 Dumontal devised a new method for the preparation of annatto, in which fermentation is avoided, and the pulp is simply washed out from the capsules and off the seeds. This product known as bixin is said to be five to six times more valuable than ordinary annatto (Crookes, "Dyeing and Calico Printing").

The colouring matters of this dyestuff were first investigated by Chevreul ("Leçons de Chimie appliquée a la Teinture "), who isolated two substances, one yellow, which was called orrellin, soluble in water, and a second, bixin, which is red and very sparingly soluble.

Bixin, the useful colouring matter, was subsequently examined by numerous chemists, who were only successful in preparing it as an amorphous powder, and its isolation in a crystalline condition was first achieved by Etti (Ber., 7, 446; 22, 864).

Etti digested 1,5 kilos, of purified annatto with a solution of 150 grammes of calcined soda ash in 2,5 kilos, of 80 per cent, alcohol on the water-bath at 80°. The "mixture was filtered and the residue pressed between warm plates, and again extracted with 1,5 kilos, of warm 60 per cent, alcohol.

The alcoholic filtrate was diluted with half its volume of water, concentrated, sodium carbonate solution added, and the crystalline precipitate of sodium bixin was collected after several days, and pressed. The product purified by solution in 60 per cent, alcohol at 70-80° and reprecipitation with sodium carbonate was finally made into a cream with alcohol, and this, when neutralised with hydrochloric acid, yielded crystalline bixin.

A simpler method has been more recently devised by Zwick (Ber., 30, 1972). Well-dried annatto is extracted for twenty-four hours with boiling chloroform, the extract evaporated, and the residue thoroughly exhausted with ligroin. The product is crystallised from chloroform, and after washing with ligroin is repeatedly recrystallised from the former solvent.

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Dyeing Properties.

Annatto is still employed to a fair extent for colouring oils and butter, but is almost extinct as a dyestuff in this country. As the orange-red colour which it yields is extremely fugitive to light, it has at no time been very extensively used. On the other hand, it resists the action of soap and dilute acids very well.

In order to dye cotton, the annatto is first dissolved in a boiling solution of carbonate of soda, and the goods are then entered and left in the bath for a quarter of an hour. They are subsequently pressed out, and washed in slightly acidulated water or alum solution.

For silk, the bath is made up with equal parts of annatto and sodium carbonate; soap is also usually added, and the dyeing is continued at 50° for about an hour, according to the shade required. The colour produced can be rendered somewhat more yellow by passing the fabric through a weak solution of tartaric acid.

Wool is dyed at 80-100° without any addition to the bath.

Eriococcus CoriaceusCHAPTER XVIII. Colouring Matters of Unknown Constitution.

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

This is a scale insect occurring in clusters consisting of small pinkish-white sacs, which encases the stems of young shoots of the Eucalypti, more especially those on old or burnt stumps. These insects contain a colouring matter which dyes wool mordanted with chromium, aluminium, tin, and iron, brown, light amber, pale orangebrown and sage-green shades respectively. The colours thus obtained are not specially brilliant, and are not fast to alkalis (Gurney, Report of the Australasian Association for the Advancement of Science, 1898. Section B, 273).

The colouring matter of cotton seed.CHAPTER XVIII. Colouring Matters of Unknown Constitution.(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Cotton seeds contain, in addition to cotton-seed oilx a phenolic substance gossypol, which remains dissolved in the oil when this is expressed.

By extracting the oil with caustic soda and neutralising the solution thus obtained a voluminous precipitate separates which consists of the colouring matter admixed with fatty acids, and the products of its own oxidation. For the isolation of gossypol Marchlewski (J, pr. Chem., 1899, 60, 84) employed a partially purified preparation of this character from which the main bulk of the fatty acids had been eliminated. By extraction with ether, repeated crystallisation from glacial acetic acid, and from a mixture of alcohol and 50 per cent, acetic acid, it was isolated in the form of small yellow prisms.

As the result of analyses of this substance dried in vacua over sulphuric acid, Marchlewski suggested two formulæ, C₁₃H₁₄O₄ and C₃₂H₃₄O₁₀, and of these the first is considered preferable. Preparations dried at higher temperatures appeared to suffer alteration as they thus became darker, and had then a lower melting-point.

Thus the gossypol when quickly heated melted at 188°, but when previously dried at 125-130°, at 179-180°. It is easily soluble in the usual organic solvents, and dissolves in sulphuric acid with a cherry-red coloration, a reaction by which its presence in cotton-seed oil can be detected. In alkalis, gossypol dissolves with a yellow coloration which rapidly changes to violet, and then slowly fades. The ready susceptibility of alkaline gossypol solutions to air oxidation accounts largely for the impure nature of the crude colouring matter isolated by such reagents from the oil, and it appears that if care is taken in the process, it is possible to obtain a much cleaner material in the first instance. An alcoholic solution of gossypol gives with ferric chloride a dark green coloration and with the neutral and basic acetates of lead a deep yellow precipitate. The analysis of the lead salt corresponded to C₁₃H₁₂O₄Pb. According to Marchlewski, gossypol yields amorphous acetyl and benzoyl derivatives and appears to possess two hydroxyl groups. It contains no methoxy groups, and is not a glucoside. It dyes iron mordanted material a grey shade, but the product obtained by a careful oxidation of its alkaline solution possesses, it is stated, tinctorial properties of greater importance. Gossypol can be employed on cotton fabrics as a mordant for the basic colouring matters.

[---]

Green EbonyCHAPTER XVIII. Colouring Matters of Unknown Constitution.(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Green ebony is a yellow dyewood formerly employed to some extent in this country, but is now almost entirely replaced by other colouring matters. It is a native of Jamaica or West India, and is obtained from the Excœcaria glandulosa (Siv.) or Jacaranda ovalifolia (R. Br.). The trunk of the tree is about 6 inches in diameter; the wood is very hard, and of an orange -brown colour when freshly cut, and stains the hands yellow. References to this dyestuff are meagre, and it does not appear to have been ever largely employed. Bancroft ("Philosophy of Permanent Colours," 1813, ii., 106) states that green ebony contains a species of colouring matter very similar to that of the Chlorophora tinctoria (Gaudich) (Old fustic), and is sometimes employed in its stead; and O. Neill ("Dictionary of Calico Printing and Dyeing," 1862) mentions that it is used in dyeing greens and other compound shades. Until recently it had a limited sale in Yorkshire as a dye for leather, but appears to have entirely passed out of use as a woollen dyestuff. It is now little used in silk dyeing, but was formerly employed for greening blacks.

Green ebony contains two crystalline colouring matters, which are distinguished by the fact that whereas one, exccecarin, is not precipitated by lead acetate solution, the second, jacarandin, is completely deposited by this reagent (Perkin and Briggs, Chem. Soc. Trans., 1902, 81, 210).

Excœcarin, C₁₃H₁₂O₅, crystallises in lemon - yellow needles, sparingly soluble in cold alcohol, and melting with effervescence at 219-22°1. It is soluble in aqueous and alcoholic alkaline solutions with a violet-red coloration, and these liquids, on exposure to air, are rapidly oxidised, and assume a brown tint.

Excœcarin does not dye mordanted fabrics, but is a substantive dyestuff in that it has a weak but decided affinity for the animal fibres with which it gives, preferably in the presence of tartaric or oxalic acid, yellow shades.

[---]

Jacarandin, C₁₄H₁₂O₆, yellow plates or leaflets, melting-point 243-245°, dissolves sparingly in alcohol and the usual solvents to form pale yellow liquids having a green fluorescence. With caustic alkali solutions it gives orange-red liquids; with alcoholic lead acetate a bright orange coloured precipitate; and with alcoholic ferric chloride a dark greenish-black solution. It dyes mordanted woollen fabrics the following shades:
Chromium. - Dull yellow-brown.
Aluminium. - Orange-brown.
Tin. - Bright golden yellow.
Iron. - Deep olive.

[---]

As indicated by Bancroft (lot. cit.) the colours given by green ebony are similar in character to those yielded by old fustic. Employing mordanted woollen cloth the following shades are produced:
Chromium. - Dull yellow-brown.
Aluminium. - Dull brown-yellow.
Tin. - Golden yellow.
Copper. - Pale brown.
Iron. - Olive-green.

Rith 40 per cent, of the dyewood the iron mordant gives greener and brighter shades than with larger amounts, in which case a browner colour is produced. Possibly from this green shade, and the extremely hard and compact nature of the wood, the name "green ebony" has originated.

Saffron.CHAPTER XVIII. Colouring Matters of Unknown Constitution.(Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Saffron consists of the dried petals of the Crocus sativus (Linn.), a plant which flowers in September and October, and is distinct from the ordinary spring crocus (Crocus vernus, All.). It is a native of the East, but is cultivated in Spain, the South of France, and Austria, and is employed for flavouring purposes, for the staining of articles of diet, and to a very limited extent as a dyestuff. Saffron contains the aromatic oil known as saffron oil, picrocrocin, a bitter compound, and crocin, or poylchroit, the glucoside of the colouring matter. Pfyl and Scheitz (Zeit. Nahr. Genussm., 1908, 16, 337) failed, however, to obtain Kayser's "picrocrocin" (Ber., 17, 2228) though using the methods employed by him. These authors state that by extraction of saffron with chloroform they isolated three products: (i) a colourless crystalline substance, melting-point 280°C., which does not reduce Fehling's solution; (ii) a yellow crystalline substance, melting-point 164°C., readily soluble in water or alcohol, which when boiled with acid developed the odour of saffron oil, and gave a sugar, probably laevulose; and (iii) a crystalline hydrocarbon, melting-point 118°C. (cf. Schiller, Diss. Munich, 1899, and Hilger), apparently similar to the hydrocarbon found in marigold petals, arnica flowers, etc. According to these authors, the second substance referred to above somewhat resembles the "picrocrocin" described by Kayser. From alcoholic extraction of saffron the same authors obtained (i) the colouring matter; (ii) a sugar (possibly laevulose); and (iii) a glucoside, which on hydrolysis yields saffron oil and a sugar (possibly lævulose).

[---]

Dyeing Properties.

Crocetin dyes aluminium and tin mordanted fabrics dull orange and yellow shades respectively.

According to Rochleder, the Chinese dyestuff "Wongsky" (q.v.), which consists of the fruit of the Gardenia grandiflora (Lour.), also contains crocin (Jour. Chem. Soc., 1858, 475).

WarasCHAPTER XVIII. Colouring Matters of Unknown Constitution.

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Waras, also called "wars" and "wurrus," consists of a purplish resinous powder which covers the seed pods of Flemingia congesta (Roxb.), an erect woody shrub growing in the thickets and forests of the warmer part of India. According to Watt ("Dictionary of Economic Products of India," iii., 482), it is collected also in Africa in the neighbourhood of Harrar, and is sent to Arabia, chiefly to Yemen and Haddramant, where it is used as a dye, as a cosmetic, and as a specific against colds. According to Wardle, waras is distinctly inferior as a dye to kamala, which it closely resembles, and contains only a small amount of colouring matter compared with the yellow vegetable dyes of commerce. It is suitable as a dye for silk rather than for wool, but is quite useless with cotton. It has been introduced into England from Aden as an adulterant or substitute for kamala (Flückiger and Hanbury's Pharmacographica, 1879, 576). Under the microscope waras appears as orange-brown lumps, frequently circular and closely resembling kamala.

Flemingin, C₁₂H₁₂O₃ (provisional), is a dull orange-red crystalline powder consisting of star-shaped groups of minute prismatic needles, which melt at 171-172°, and closely resembles the rottlerin of kamala. Solutions of the alkali hydroxides dissolve it with an orangebrown tint, but these solutions when boiled do not deposit resinous matter, as is the case with rottlerin. On fusion with alkali salicylic acid and acetic acid are produced.

Silk suspended in a solution of flemingin in dilute sodium carbonate, and the whole gradually raised to the boiling temperature, is dyed golden yellow, slightly duller than the shade given by rottlerin; but, on the other hand, flemingin possesses much the stronger dyeing power of the two.

In addition to flemingin waras contains a trace of a yellow crystalline colouring matter, homoflemingin, melting-point 165-166° (C = 69,97; H = 5,75), together with some quantity of two resinous substances: (a) C₁₂H₁₂O₃ (?), melting-point 162-167°, and (b) C₁₃H₁₄O₃ (?), melting below 100°. Fused with alkali these latter gave salicylic and acetic acids, and appear to be allied to flemingin.

Added to a boiling solution of its own weight of sodium carbonate, waras dyes silk golden yellow shades, which are brightened by rinsing in very dilute acetic acid. Contrary to the statement of Wardle, it is to be regarded as a decidedly superior dyestuff to kamala (Perkin, Chem. Soc. Trans., 1898, 73, 659).

KamalaCHAPTER XVIII. Colouring Matters of Unknown Constitution. (Osa artikkelista)

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

Kamala or Kamela is the orange-red powder which exists as a glandular pubescence on the exterior of the fruits of the Mallotus phillipinensis, Muell. (Rottlera tinctoria, Roxb.), a small evergreen tree, met with throughout tropical India, Burma, and Ceylon, also in Java, China, the Malay Islands, and Australia. The ripe capsules are gathered in February or March, and shaken in bags until the powder separates.

Kamala is employed by the Hindoos as an antithelmic drug and for dyeing silk and wool a bright orange colour. The fabric is dyed in a boiling bath containing 4 parts kamala, i part alum and 2 parts sodium carbonate (native barilla), previously wellrubbed together in the powdered state with a small quantity of oil of sesamum. The alum is sometimes omitted, but the addition of alkali is absolutely necessary in order to dissolve the colouring matter, which is of a resinous character and quite insoluble in water. Kamala is also apparently used for the adulteration of annatto, for according to Perkin (private communication), samples of calico obtained from India and presumably dyed with kamala have proved on examination to owe their colour partially if not entirely to annatto. Kamala was formerly employed in this country as a remedy for taenia, but appears now to be very little used for this purpose.

[---]

According to Hummel and Perkin (J. Soc. Chem. Ind., 1895, 14), for silk dyeing it is best to add i part of kamala and 0,5-1 part sodium carbonate to boiling water, then to enter the silk and to dye at the boiling temperature for two to five minutes only. Other experiments indicated that the amount of sodium carbonate to employ should be regulated by the quantity of water used rather than by that of the kamala, namely, at the rate of 13-14 grams (Na₂CO₃, 10 aq) per litre. After dyeing fora short time with the addition of alkali only, to the extent of one-fifth of the weight of the kamala used, the addition of alum or stannous chloride to the dye-bath makes the colour fuller and more orange. A similar but by no means identical effect is obtained by making a slight addition of sulphuric acid.

As pointed out by Perkin (loc. cit.}, rottlerin is decomposed by boiling sodium carbonate solution, and the colour ultimately fixed on the fibre most probably consists of rottlerone. Although rottlerin itself does not dye mordanted fabrics, the potassium and sodium salts of this colouring matter give on calico mordanted with aluminium and iron pale orange-red and brownish-black shades.

Pure Java kamala contains, according to Flückiger (Arch. Pharm., 1892), 1,363 to 1,488 per cent, of ash, whereas in the kamala examined by Anderson (loc. cit.) 3,49 per cent, was present. The best commercial varieties usually contain about 5 per cent, of mineral matter (Seidler and Waage, Ber. Deut. pharm. Ges., 1891, 80); but the inferior qualities are highly adulterated (50-87 per cent.) with sand, earthy impurities, red brick-dust, etc. (Perkin, loc. cit., and J. Soc. Chem. Ind., 1900

Species of CoprosmaCHAPTER XVIII. Colouring Matters of Unknown Constitution.

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

The bark, and more especially the roots, of the C. grandiflora, C. linariifolia, and C. areolata, which belong to the natural family of the Rubiaca, and are widely distributed in New Zealand, possess tinctorial property (Aston, New Zealand, J. Sci. Tech.,1918, 1, 3), and being related to madder probably contain either alizarine itself or an allied colouring matter. Thus an alcoholic extract of the C. grandiflora is coloured purple by alkali, and becomes yellow on addition of acid. From the acid solution, by means of ether, an orange-yellow crystalline substance can be isolated in small amount.

SafflowerCHAPTER XVIII. Colouring Matters of Unknown Constitution.

The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918

Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.

This dyestuff consists of the dried florets of Carthamus tinctoria (Linn.), an annual thistle-like plant belonging to the Cynarocephalce. A native of Southern Asia, it has been cultivated in China, India, Persia, Egypt, also in central and southern Europe. When in full bloom the yellow florets are plucked, and either at once dried, so as to form an orange-coloured fibrous mass somewhat resembling saffron, or they are first kneaded with water, in order to remove a useless yellow colouring matter, and then pressed into the form of lens-shaped cakes and dried.

Safflower owes its value to an insoluble red colouring matter which occurs only in very small amount, about 0,5 per cent., whereas the soluble yellow colouring matter is said to be present to the extent of about 30 per cent.

The yellow colouring matter may be obtained by first precipitating a cold aqueous extract of safflower with lead acetate and acetic acid and then adding ammonia to the filtrate, i.e. precipitating with basic lead acetate. The second precipitate thus obtained is carefully decomposed with dilute sulphuric acid, and after removing the lead sulphate the filtrate is evaporated to dryness with exclusion of air. It is thus obtained as an amorphous substance, having acid properties, a bitter taste, and a peculiar odour. It is of a very unstable character, and on exposure to air seems to oxidise, becoming brown and partially insoluble in water. According to Schlieper, its composition is represented by the formula C₁₆H₂₀O₁₀; according to Malin, it is C₂₄H₃₀O₁₅. This product is apparently a glucoside or contains a substance of this character, for after digestion with boiling dilute sulphuric acid, the solution yields to ether a small quantity of a crystalline yellow colouring matter (Perkin, private communication).

Carthamin or carthamic acid is the name given to the useful red colouring matter, which, although insoluble in water, is readily soluble in alkaline solutions. To obtain it, safflower is well washed with slightly acidified water to remove the yellow colouring matter, then it is steeped for some time in a cold dilute solution of sodium carbonate. If the alkaline solution be now acidified with acetic or tartaric acids the carthamin is precipitated in so finely divided a condition that it cannot be successfully collected. This difficulty is, however, obviated by making use of the fact that carthamin is readily attracted and removed from its acidified solution by cellulose. Hence bleached cotton is immersed and moved about in the alkaline solution, which is at the same time gradually acidified with tartaric or citric acid.

In this manner the carthamin is slowly precipitated and is at once attracted by the cotton, which thus becomes dyed red. After washing the dyed cotton with slightly acidified water, the colouring matter is dissolved off by means of a dilute solution of sodium carbonate, from which the carthamin is thrown down, on the addition of tartaric acid, as a bright- red precipitate, which is now in a purer and more granular form. Further purification is effected by dissolving the dried precipitate in alcohol and reprecipitating with water.

[---]

Previous to the discovery of safranine and of the eosins, safflower was frequently used for the production of brilliant pinks or reds, chiefly on cotton or silk. The mode of dyeing is practically the same as that already given in describing the process of obtaining carthamin. The safflower in bags is well washed with cold water, in order to remove the yellow colouring matter, and the red colouring matter is then extracted by a treatment with a cold dilute solution of sodium carbonate. In this solution the material to be dyed is worked about, at the same time adding "lime juice" (citric acid) gradually until in slight excess. Safflower extract is applied in a similar manner.

Dyers usually gave the washed safflower several successive treatments with alkali, employing at first weak and afterwards strong alkaline solutions. The weak solutions give the brightest and purest tints; hence very delicate colours were dyed with these alone, whilst full colours were first dyed with the inferior extracts, and then "topped" or "bloomed" by a dyeing in the purer solutions. The shades obtained from safflower were at one time considered to be the finest and most delicate a dyer could produce. On the other hand, they were not only expensive but had the disadvantage of being extremely unstable.

Safflower is a very weak dyestuff, for 4 oz. are necessary to dye 1 lb. of cotton light pink, 8 oz. for a rose-pink, and about 1 lb. to produce a full crimson.

It is now rarely, if ever, employed in Europe as a dyestuff, but large quantities are still cultivated, more especially in India, and used for dyeing and pigment manufacture in the East.

Carthamin was sold in a more or less pure condition as a thin aqueous paste, under the name of safflower extract or safflower carmine, but this product is now difficult to obtain in Europe. On the other.hand, considerable quantities are still manufactured in Japan, where it is very largely employed as a cosmetic. Carthamin ground up with starch, talc, etc., is used as rouge.

For other references, v. Dumas, Annalen, 27, 147; Liebermann, Ber., 7, 247; 8, 1649; Dobereiner, J. Phys. Chem., 26, 266; Salvetat, Ann. Chim. Phys., (3), 25, 337; J. pr. Chem., 44, 475; Dufour, Ann. Chim. Phys., 48, 283.