On Cotton Seeds.
By PROF. F. A. FLÜCKIGER.
From an excellent monograph on this subject, reprinted from the June number of N. Jahrb. f. Pharm., and communicated by the author, we make the following, extracts:
Linnaeus described five distinct cotton plants: Gossypium arboreum, G. herbaceum, G. barbadense, G. hirsutum and . Recently Parlatore, in his monograph, "Le Specie dei Cotoni," (Firenze, 1866, 64 pp. 4to., 6 folio plates) confirmed these species, and added two more from Polynesia—G. sandvicense and G. taïtense. The eighth species, G. anomalum, Wawra et Peyritsch (G. senarense, Fenzl,) belongs to tropical Africa. (Oliver, flora of tropical Africa, I, London, 1868, 211. G. anomalum is remarkable for the linear and entire parts of the epicalyx.) All these plants are perennial; but only G. religiosum produces stout stems, about twenty-five feet in height; the stems of the others become woody, reach, however, barely a height of four meters, with a diameter of a few centimeters. When cultivated, they mostly become annual or biennial, and remain herbaceous.
The first two species in the above list belong to the hot countries of Asia, and were known in early history. The Florentine museum has capsules and seeds from ancient Egyptian sepulchres, which, according to Parlatore, are derived from G. arboreum. Theaphrastos, (Hist. plantar. 4, 7, 7.) in the fourth century before Christ, described a cotton plant. G. barbadense, hirsutum and religiosum originally inhabited the tropical parts of America, particularly Central America and the West Indies; the former is now most extensively cultivated in consequence of the excellence of its cotton. In the Southern States of North America it yields the valued Georgia, or Sea Island cotton; it is also cultivated in Western Africa, Egypt, East Indies and Australia. G. hirsutum is distributed to the same extent, and grows well in Southern Italy; the upland cotton, short staple, Siam, Castellamare, and Malta cotton comes from this species. G. religiosum, probably indigenous to Peru, requires a warmer climate, but is cultivated in some localities south of the Mediterranean. G. herbaceum, owing to the small capsule, gives a smaller yield; its purely white fibre, however, is better than that of G. arboreum, which yields the lowest grade of cotton. The species from Polynesia and Central Africa appear not to be cultivated yet.
Like all the extensively cultivated plants which are spread over a considerable area, we find in this genus numerous varieties which are distinguished with difficulty in consequence of the confusion existing in their nomenclature. Parlatore found, even in botanical gardens, varieties of G. religiosum under the name of G. arboreum.
The cotton fibres, which originate from the cells of the epidermis of the testa, are readily removed from the seeds of G. barbadense; they adhere more firmly in G. anomalum, hirsutum, sandvicense and taitense. G. religiosum has the spinning fibres not firm, but besides them, the testa has a brown reddish covering of short hairs. G. arboreum and herbaceum have seeds to which not only the cotton, but also the greenish or greyish felt-like covering firmly adhere.
The removal of the spinning fibres, by peculiar machines, without touching the felt cover, is accomplished with almost perfectness from G. barbadense, while, owing to the described structure, the cotton is rather torn off from the seeds of the other species. The excellence of the sea island cotton and some other varieties partly depends upon this difference.
The anatomical structure of the seeds is then minutely described and illustrated by microscopical drawings of sections of the testa and of a cotyledon.
The complicate contents of the large tannin cells in the cotyledons, containing also granules of a beautiful violet coloring matter, are dissolved by the oil, if this is expressed, and impart to the latter an unsightly brown color, even if the testa had been previously removed.
The cotton seed oil is of a mild taste, non-drying and congeals somewhat below 0° C. According to Slessor, (Jahresb. d. Chemie, 1866, p. 366, Gmelin, Organ. Chem.) it consists mainly of olein and palmitin; the author, however, did not succeed to readily prove the presence of olein by testing with hyponitric acid.
For technical purposes, it ranks with benne seed (= sesame seed) and olive oil, provided it be obtained colorless or faintly yellow. It is exported in large quantities, partially purified, from England, (Dingler's Polytechn. Journ., 1865, p. 236. ) and from Marseilles (Authentic private information.) to Italy, whence it is re-exported as olive oil. 50,000 gallons of cotton seed oil were expressed in St. Louis, Mo., in 1868, and a factory in Providence, R. I. turns out a sweet golden yellow oil, (Sold under the name of salad oil.—M.) the process of purification being kept secret; it is probable that the crude dark-brown oil is treated with lye, and a similar process appears to be in use in Marseilles. Heated with alkalies, insufficient for saponification, most of the color is removed, including the coloring matter mentioned before, which may, perhaps, be made available for dyeing.
Cotton seed oil, in its crude state, is colored purple by concentrated sulphuric acid, and if bichromate of potassa be added at the same time, blood red; potassa colors it yellowish, and in contact with the air finally bluish purple. After the first reaction, water will separate a matter which dissolves with beautiful colors, ranging between blue and red, in alcohol, chloroform, bisulphide of carbon, potassa, sulphuric acid and ether; if these colors could be fixed an excellent dye stuff would be gained. This body is probably formed by the splitting of a tannin; Kuhlmann (Jahresber. d. Chemie, 1861, 944.) found in it 68.9 carbon and 8.2 hydrogen.
Nitric acid of spec. grav. 1.2 imparts to the purified oil a very faint yellowish color; a cold mixture of equal parts of nitric and sulphuric acid renders it red brown.
The yield in oil, aside from the species and from climatic influences, varies with the treatment of the seeds; the felt cover, amounting sometimes to 14 per cent. of the weight, if present during the expression, must retain considerable of the oil; 15-29 per cent. of oil have been obtained, and after the removal of the testa 31 to over 50 per cent. The economic value of cotton seed rests mainly in the fact that the oil may be obtained in enormous quantities as a by-product.
Calculated from the nitrogen found, the seeds contain about 23 per cent. and the kernels about 32 per cent. of protein compounds, showing the value of the press cakes as feed or manure.
From 3.7 to 6.78 per cent. of ashes have been obtained from the seeds, 2.33 per cent. from the testa, 4.3 to 8.9 from the kernels. The amount of water is 8 to 9 per cent.; of gum and sugar together 7.5 to 14 per cent. The seeds leave 25 per cent., the kernels only 7 per cent. of cellulose.
Though the use of the cotton fibre is of the highest antiquity, the oil of the seeds was not employed. It appears that the first suggestion for utilizing the oil emanated from the London Society for Encouragement of Arts and Science, in 1785, but, even in the United States, the oil was little known in 1856; very little of it is still made in Brazil, and the amount obtained in Marseilles from West African seeds is not considerable. London manufactures the most, from seeds imported from the Indies and North America; but the production is neither as extensive or as regular as it might be.
The annual production of cotton is estimated at over 1000 millions kilogrm., of which the United States produce about 600 millions kilogrm. The author obtained from two ripe capsules for 1000 parts cotton 2520 and 1730 parts seeds. Alcan, in his "Traité complet de la filature du coton," Paris, 1865, states that the proportion between cotton and seeds is very variable, but that in the mean four parts of crude cotton yield one part of spinning fibre, leaving three parts for the seed and offal, so that the annual production of seeds would be between 2000 and 3000 millions kilogrm. But if the cotton seeds are estimated only at 1000 millions kilogrm., there might be obtained at least 150 millions kilogrm. of oil. In Marseilles, 100 kilogrm. of crude cotton seed oil are valued at 80 francs, the purified at 105 to 110 francs; the above quantity would therefore represent a value of 120 millions of francs. The 500 to 700 millions kilogrm. press cakes would probably have to be valued at 20 to 30 millions francs.
Though these figures may appear to be arbitrary, they serve, at least, to show how much remains to be done in the future for the proper utilization of these seeds.
J. M. M.