DIE KÜNSTLICHE SEIDE-IHRE HERSTELLUNG, EIGENSCHAFTEN UND VERWENDUNG.
Carl Süvern, Berlin, 1900, J. Springer.
ARTIFICIAL SILK—ITS PRODUCTION, PROPERTIES, AND APPLICATIONS.
This work of some 130 pages is an important monograph on the subject of the preparation of artificial cellulose threads—so far as the technical elements of the problems involved are discussed and disclosed in the patent literature. The first section, in fact, consists almost exclusively of the several patent specifications in chronological order and ranged under the sub-sections: (a) The Spinning of Nitrocellulose (collodion); (b) The Spinning of other Solutions of Cellulose; (c) The Spinning of Solutions of the Nitrogenous Colloids.
In the second section the author deals with the physical and chemical proportions of the artificial threads.
Chardonnet 'silk' is stated to have a mean diameter of 35µ, but with considerable variations from the mean in the individual fibres; equally wide variations in form are observed in cross-section. The general form is elliptical, but the surface is marked by deep striæ, and the cross-section is therefore of irregular outline. This is due to irregular conditions of evaporation of the solvents, the thread being 'spun' into the air from cylindrical orifices of regulated dimensions. Chardonnet states that when the collodion is spun into alcohol the resultant thread is a perfect cylinder (Compt. rend. 1889, 108, 962). The strength of the fibre is variously stated at from 50-80 p.ct. that of 'boiled off' China tram; the true elasticity is 4-5 p.ct., the elongation under the breaking strain 15-17 p.ct. The sp.gr. is 1.49, i.e. 3-5 p.ct. in excess of boiled off silk.
Lehner 'silk' exhibits the closest similarity to the Chardonnet product. In cross-section it is seen to be more regular in outline, and a round, pseudo-tubular form prevails, due to the conditions of shrinkage and collapse of the fibre in parting with the solvents, and in then dehydrating. The constants for 'breaking strain,' both in the original and moistened condition, for elasticity, &c., are closely approximate to those for the Chardonnet product.
Pauly 'silk'.—The form of the ultimate fibres is much more regular and the contour of the cross-section is smooth. The product shows more resistance to moisture and to alkaline solutions.
Viscose 'silk' is referred to in terms of a communication appearing in 'Papier-Zeitung,' 1898, 2416.
In the above section the following publications are referred to: Chardonnet, 'Compt. rend.,' 1887, 105, 900; and 1889, 108, 962; Silbermann, 'Die Seide,' 1897, v. 2, 143; Herzog, 'Farber-Zeitung,' 1894/5, 49-50; Thiele, ibid. 1897, 133; O. Schlesinger, 'Papier-Zeitung,' 1895, 1578-81, 1610-12.
Action of Reagents upon Natural and Artificial Silks.
1. Potassium hydrate in solution of maximum concentration dissolves the silks proper, (a) China silk on slight warming, (b) Tussah silk on boiling. The cellulose 'silks' show swelling with discolouration, but the fibrous character is not destroyed even on boiling.
2. Potassium hydrate 40 p.ct. China silk dissolves completely at 65°-85°; Tussah silk swells considerably at 75° and dissolves at 100°-120°. The cellulose 'silks' are attacked with discolouration; at 140° (boiling-point of the solution) there is progressive solvent action, but the action is incomplete. The Pauly product is most resistant.
3. Zinc chloride, 40 p.ct. solution. Both the natural silks and lustra-celluloses are attacked at 100°, and on raising the temperature the further actions are as follows: China silk is completely dissolved at 110-120°; Tussah silk at 130-135°; the collodion products at 140-145°; the Pauly product was again most resistant, dissolving at 180°.
4. Alkaline cupric oxide (glycerin) solution was prepared by dissolving 10 grs. of the sulphate in 100 c.c. water, adding 5 grs. glycerin and 10 c.c. of 40 p.ct. KOH. In this solution the China silk dissolved at the ordinary temperature; Tussah silk and the lustra-celluloses were not appreciably affected.
5. Cuprammonium solution was prepared by dissolving the precipitated cupric hydrate in 24 p.ct. ammonia. In this reagent also the China silk dissolved, and the Tussah silk as well as the lustra-celluloses underwent no appreciable change.
6. An ammoniacal solution of nickel oxide was prepared by dissolving the precipitated hydrated oxide in concentrated ammonia. The China silk was dissolved by this reagent; Tussah silk and the lustra-celluloses entirely resisted its action.
7. Fehling's solution is a solvent of the natural silks, but is without action on the lustra-celluloses.
8. Chromic acid—20 p.ct. CrO3—solution dissolves both the natural silks and the lustra-celluloses at the boiling temperature of the solution.
9. Millon's reagent, at the boiling solution, colours the natural silks violet: the lustra-celluloses give no reaction.
10. Concentrated nitric acid attacks the natural silks powerfully in the cold; the lustra-celluloses dissolve on heating.
11. Iodine solution (I in KI) colours the China silk a deep brown, Tussah a pale brown; the celluloses from collodion are coloured at first brown, then blue. The Pauly product, on the other hand, does not react.
12. Diphenylamine sulphate.—A solution of the base in concentrated sulphuric acid colours the natural silks a brown; the collodion 'silks' give a strong blue reaction due to the presence of residual nitro-groups. The Pauly product is not affected.
13. Brucin sulphate in presence of concentrated sulphuric acid colours the natural silks only slightly (brown); the collodion 'silks' give a strong red colouration. The Pauly product again is without reaction.
14. Water.—The natural silks do not soften in the mouth as do the lustra-celluloses.
15. Water of condition was determined by drying at 100°; the following percentages resulted (a). The percentages of water (b) taken up from the atmosphere after forty-three hours' exposure were:
| (a) | (b) | |
| China (raw) silk | 7.97 | 2.24 |
| Tussah silk | 8.26 | 5.00 |
| Lustra-celluloses: | ||
| Chardonnet (Besançon) | 10.37 | 5.64 |
| " Spreitenbach | 11.17 | 5.77 |
| Lehner | 10.71 | 5.97 |
| Pauly | 10.04 | 6.94 |
16. Behaviour on heating at 200°.—After two hours' heating at this temperature the following changes were noted:
| China silk | Much discoloured (brown). |
| Tussah silk | Scarcely affected. |
| Lustra-celluloses: | |
| Chardonnet | Converted into a blue-black charcoal, retaining the form of the fibres. |
| Lehner | |
| Pauly | A bright yellow-brown colouration, without carbonisation. |
17. The losses of weight accompanying these changes and calculated per 100 parts of fibre dried at 100° were:
| China silk | 3.18 |
| Tussah silk | 2.95 |
| Lustra-celluloses: | |
| Chardonnet | 33.70 |
| Lehner | 26.56 |
| Pauly | 1.61 |
18. Inorganic constituents.—Determinations of the total ash gave for the first five of the above, numbers varying from 1.0 to 1.7 p.ct. The only noteworthy point in the comparison was the exceptionally small ash of the Pauly product, viz. 0.096 p.ct.
19. Total nitrogen.—The natural silks contain the 16-17 p.ct. N characteristic of the proteids. The lustra-celluloses contain 0.05-0.15 p.ct. N which in those spun from collodion is present in the form of nitric groups.
The points of chemical differentiation which are established by the above scheme of comparative investigation are summed up in tabular form.
Methods of dyeing.—The lustra-celluloses are briefly discussed. The specific relationship of these forms of cellulose to the colouring matters are in the main those of cotton, but they manifest in the dye-bath the somewhat intensified attraction which characterises mercerised cotton, or more generally the cellulose hydrates.
Industrial applications of the lustra-celluloses are briefly noticed in the concluding section of the book.