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.
True sumach consists of the dried and usually powdered leaves of the genus Rhus (order Terebinthacæ], and is useful for tanning the finer kinds of leather, and also in dyeing and calico printing on account of the tannin matter present in it.
Sicilian sumach, the variety most esteemed in this country and throughout Europe, consists of the leaves of the Rhus coriaria (Linn.), a shrubby bush cultivated to a large extent in Sicily, where the sumach industry is of considerable importance. When the plant is about to flower the younger twigs are removed, dried in the sun, and subsequently beaten to remove the leaves and flower panicles. The sumach is imported sometimes in leaves, but more often in the form of powder, and should contain about 25 per cent, of tannin, although as much as from 27-32 per cent, may occasionally be found.
According to Löwe (Zeitsch. anal. Chem., 12, 128), the tannin matter present, C14H10O9, is ordinary gallotannin; indeed it is well known that when an aqueous extract of the sumach is boiled with dilute sulphuric acid, considerable quantities of gallic acid are produced. On the other hand, Strauss and Geschwender (Zeitsch. angew. Chem., 1906, 1121), who isolated the tannin according to Löwe's instructions, detected the presence of a methoxy group, and suggest the formula C32H29O11.OMe.
Sicilian sumach contains also a trace of an ellagitannin and myricetin, C16H10O8, to the extent of about 0,1173 per cent. (Perkin and Allen, Chem. Soc. Trans., 1896, 69, 1299), the latter colouring matter having been previously mistaken by Löwe (Zeitsch. anal. Chem., 1874, 12, 127) for quercetin.
Considerable quantities of sand and sometimes particles of magnetic iron ore, which cause black stains, are often to be found in sumach (Procter, "Principles of Leather Manufacture," 1903, 271); (compare also Trotman, J. Soc. Chem. Ind., 1904); and it is frequently highly adulterated in the ground condition with the leaves and twigs of various plants. Of these, the Pistacia lentiscus (Linn.) ("schinia" or "skens"), Coriaria myrtifolia (Linn.), (French sumach or "stinco"), Tamarix africana (Poir.) (brusca), Tamarix gallica (Linn.), Ailanthus glandulosa (Desf.), Ficus carica (Linn.), Vitis vinifera (Linn.), other species of the Rhus family and also the ground branches ("gambuzza," "gammuzza") of the Rhus coriaria itself, are known to be employed. These sumach adulterants also contain tannin matters, but for tanning and dyeing purposes are as a rule much inferior to sumach itself.
The Pistacia lentiscus (Linn.), (mastic tree), a small tree about 20 feet high with evergreen leaves, grows abundantly in Cyprus. The leaves of this plant constitute the most important sumach adulterant, and about 10,000 tons are said to be exported from Tunis to Sicily annually and re-exported thence (as sumach?). According to Procter (loc. cit.) the leaves contain 12-19 per cent, of a catechol tannin. A good plump leather can be obtained from this material, but of a faintly reddish tint, the result being intermediate in character between those which are given by oak bark and sumach. Its presence in sumach is to be deprecated, and in many cases leads to injurious results. A considerable quantity, however, is consumed at Lyons in France as an assistant dyeing material for silk stuffs.
According to Perkin and Wood (Chem. Soc. Trans., 1898, 73, 374), these leaves contain a tannin closely allied to, if not identical with, ordinary gallotannic acid, as when an aqueous extract is boiled with dilute sulphuric acid a considerable quantity of gallic acid is produced. A second tannin or tannin glucoside is also present which, although possessing the general characteristics of the socalled "catechol" tannins in that it yields a red phlobaphene, and as noted by Procter, a reddish-coloured leather, gives, by fusion with alkali, gallic acid and phloroglucinol.
In addition to these tannins, myricetin (probably as glucoside) C15H10O8 is also present to the extent of about 0,15 per cent.
Tamarix africana (Poir.) is a small shrub or tree characterised by its twiggy branches and minute scale-like leaves. The small twigs are collected in Tunis and imported into Sicily for the adulteration of sumach (Procter).
According to Perkin and Wood (loc. cit.} the leaves contain a tannin probably identical with gallotannin, in addition to a small quantity of an ellagitannin. A trace of yellow colouring matter is also present and consists of a quercetin methylether, C16H12O7.
The Tamarix gallica (Linn.) closely resembles in appearance the Tamarix africana and flourishes in Cyprus, where the latter is not found. According to Procter, it contains 8,4 per cent, of tannin matter.
Ailanthus glandulosa (Desf.) is a tree of large size and handsome appearance, native of India and China, but common on the Continent. The leaves contain 11,2 per cent, of tannin matter (Procter), and this resembles gallotannin, although a trace of an ellagitannin is also present (Perkin and Wood). Curiously enough, although so high a percentage of tannin is present, leather is scarcely tanned by an extract of these leaves, but is merely stained a dull dirty colour. This material is therefore of little use for tanning purposes, and as an adulterant of sumach exerts a deleterious influence. A small quantity of quercetin can be isolated from the leaves.
The leaves of the Ficus carica (Linn.) (common fig tree) contain 1,6 per cent, of tannin (Procter) and a trace of a yellow colouring matter (Perkin and Wood). Skin is untanned by an extract of these leaves, but acquires, during the process, a dirty olive tint.
Gambuzza consists of the small stalks branching from the main root of the Rhus coriaria (Linn.), which are ground to powder and mixed with sumach. The material contains some quantity of a tannin resembling gallotannin, together with a trace of myricetin.
Attempts to detect the presence of these adulterants in sumach by chemical methods have not given satisfactory results, but should a prolonged boiling of the extract with dilute sulphuric acid cause the gradual precipitation of phlobaphene, the presence of the leaves of the Pistacia lentiscus may be suspected.
More satisfactory results can be obtained by microscopical examination, and an elaborate work on this subject has been carried out by Andreasch ("Sicilianischer Sumach und seiner Verfalschung," Wien, 1898); the book, however, is unsuitable for abstraction. A useful method, now generally adopted by leather trades chemists, has been devised by Lamb and Harrison (J. Soc, Dyers, 1899, 14, 60), and is based upon the behaviour of the leaf mixture with warm nitric acid. Under such treatment, the more delicate leaf structure of sumach itself is completely destroyed, whereas the strong cuticles of Pistachia lentiscus, Coriaria myrtifolia, Tamarix africana, and Ailanthus glandulosa, are unaffected and can then be readily recognised (compare also Lamb, ibul. t 1904, 20, 265). Again, the leaves of the R. coriaria are very easily distinguished from those of other plants employed for their adulteration, in that both upper and lower cuticles are covered with a dense growth of hairs (Priestman, J. Soc. Chem. Ind., 1905, 24, 231).
Venetian sumach or Turkish sumach consists of the leaves of the Rhus cotinus (Linn.), a small tree, the wood of which constitutes the yellow dyestuff known as "Young Fustic". The material contains about 17 per cent, of tannin, which resembles ordinary gallotannin, together with a trace of an ellagitannin. The presence of myricetin, C15H4O2(OH)6, in these leaves is interesting, in view of the fact that in the wood itself, fisetin, C15H6O2(OH)4, is present (Perkin, Chem. Soc. Trans., 1898, 73, 1016).
American sumach. The leaves of numerous varieties of Rhus are employed in the United States for tanning and dyeing purposes, and of these the R. glabra (Linn.) very largely takes the place of Sicilian sumach. It contains about 25 per cent, of a tannin closely resembling gallotannin, but produces a leather of very much darker colour than the Sicilian product.
Of the other varieties, R. typhina (Linn.) or "Virginian sumach" (10-18 per cent.), R. cotinoides (Nutt.) (21 per cent.), R. semialata (Murr.) (5 per cent), R. aromatica (Ait.) (13 per cent.) (Procter), R. metopium (Linn.) (about 8-2 per cent, of tannin, probably gallotannin, together with traces of both quercetin and myricetin), (Perkin, Chem. Soc. Trans., 1900, 77, 427), R. copallina (Linn.), R. pumila (Michx.), and R, toxicodendron (Linn.), are to be found in the States. Among these, R. glabra and R. copallina are considered to be worthy of extended cultivation.
In India, numerous species of the genus Rhus are known to exist (Watt's Dictionary, "Economic Products of India "), and again in Algeria the R. pentaphylla (Desf.) is used by the Arabs for tanning goat-skins. Finally, the Anaphrenium argenteum (E. Mey), (R. thunbergii). (Cape of Good Hope), 28 per cent, of tannin (bark), probably of the catechol class (Procter), and the Rhodosphaera rhodanthema (Engl.) (Rhus rhodanthema) (New South Wales), 9-5 per cent, of tannin (leaves), resembling gallotannin, are worthy of mention. The latter plant, also known as the "yellow cedar," closely resembles the R. cotinus, and it is interesting to note that although the wood of this tree contains fisetin, C15H4O2OH)4 the colouring matter of the leaves is quercetin, C15H3O2(OH)6 (Perkin Chem. Soc. Trans., 1898, 73, 1017).
French sumach is derived from the Coriaria myrtifolia (Linn.), a low deciduous shrub, native of Southern Europe, and has been referred to above as an adulterant of Silician sumach. In addition to tannin (15,6 per cent., Procter), which consists probably of ordinary gallotannin together with a little ellagitannin, it contains the poisonous glucoside coriamyrtin (Riban, Chem. Zeit, 1867, 663) and a trace of quercetin (Perkin, Chem. Soc. Trans., 1900, 77, 428). According to Procter, the colour of leather tanned by these leaves is very satisfactory and practically equal to that produced by genuine sumach (R. coriaria). It is also employed in black dyeing.
Cape sumach consists of the leaves of the Colpoon compressum (Berg.) (Osyris compressa, Fusanus compressus, Thesium colpoon), and is much used in South Africa under the name of "Pruimbast". The bush is found in the mountains, where it grows to the height of about 6 feet, and only the younger leaves are gathered. These leaves contain about 23 per cent, of tannin (Procter), which has been isolated as a hygroscopic transparent glassy mass and is probably a phlobatannin glucoside. With boiling dilute acid, a reddishbrown phlobaphene gradually separates, and on fusion with alkali protocatechuic acid is produced (Perkin, Chem. Soc. Trans., 1897, 71, 1135). In addition to tannin there is also present a considerable quantity of the quercetin glucoside Rutin (Osyritrin) (Chem. Soc. Trans., 1910, 98, 1776). According to Procter, this material forms a useful substitute for Sicilian sumach.
In lieu of the Colpoon compressum, a tanning agent known as "broach leaves" (botanical origin lacking) appears to be considerably employed in South Africa. It contains about 19,9 per cent, of tannin of the so-called "catechol" variety, together with traces of both quercetin and myricetin (Chem. Soc. Trans., 1898, 73, 384).
Russian sumach consists of the leaves of the Arctostaphylos uvaursi (Spreng.) (Bearberry), and is said to contain about 14 per cent, of tannin, which, according to Perkin (Chem. Soc. Trans., 1900, 77, 424), consists of a gallotannin together with traces of an ellagitannin. Minute amounts of both quercetin and myricetin have been isolated from this material.
Considerable quantities of "sumach extract" are now manufactured for dyeing and tanning purposes from genuine Sicilian sumach, and this is usually found on the market as a brown treacly liquid of about 52° Tw. So-called decolorised extracts are also prepared to compete with ordinary tannic acid, and for this purpose the addition of blood albumen to the dilute extract at about 48°, then raising the temperature to 70°, and subsequently filter-pressing, gives the most satisfactory results. Sulphurous acid again is employed to brighten the colour of extracts, and acts partly as a weak acid in decomposing the inorganic salts of the tannin or colouring matter and partly as a reducing agent. In this case it is usual to pass sulphur dioxide through the liquor before concentration (Procter).
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