Читать книгу A Text-book of Paper-making - C. F. Cross - Страница 12

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—When cotton is treated with 30 times its weight of sulphuric acid somewhat diluted (1 part H2O, 4 parts H2SO4) it quickly dissolves, the solution being at first gelatinous, becoming afterwards syrupy. On pouring this solution into water, a white flocculent precipitate is formed, consisting of a substance closely resembling the cellulose from which it is derived, differing, indeed, only in being amorphous, and in being coloured blue by iodine. This substance, from its resemblance to starch, has been called amyloid. When sufficiently dehydrated it constitutes a swollen starchy mass, which dries to a brittle transparent solid. This transformation appears to consist in a simple hydration of the cellulose molecule, thus:—2 (C6H10O5)

Cellulose.

+

H₂O

=

C12H22O11.

Amyloid.

The modification of cellulose, which occurs on the conversion of unsized paper into the so-called parchment paper, by exposure for a short time to the action of strong sulphuric acid, and subsequent washing and drying, consists doubtless in a superficial conversion of the cellulose into amyloid, or a body closely resembling it.