Part 7 (1/2)

3. _Zinc chloride_, 40 p.ct. solution. Both the natural silks and l.u.s.tra-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 l.u.s.tra-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 l.u.s.tra-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 l.u.s.tra-celluloses entirely resisted its action.

7. _Fehling's solution_ is a solvent of the natural silks, but is without action on the l.u.s.tra-celluloses.

8. _Chromic acid_--20 p.ct. CrO_{3}--solution dissolves both the natural silks and the l.u.s.tra-celluloses at the boiling temperature of the solution.

9. _Millon's reagent_, at the boiling solution, colours the natural silks violet: the l.u.s.tra-celluloses give no reaction.

10. _Concentrated nitric acid_ attacks the natural silks powerfully in the cold; the l.u.s.tra-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 l.u.s.tra-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

l.u.s.tra-celluloses:

Chardonnet (Besancon) 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.

l.u.s.tra-celluloses:

Chardonnet Converted into a blue-black charcoal, retaining the Lehner form ofthe fibres.

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