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 |