Pecto-Cellulose.
| 43·7 | per cent. | C. |
| 5·9 | „ | H. |
On boiling with an alkali it loses in weight about 20 per cent., the substance dissolved being identical in properties with Frémy’s pectic acid, a substance containing 42 per cent. C and 4.8 per cent. H = C16H22O15. Many other bast fibres, as well as cellulose tissues, exhibit similar properties, and although this branch of the subject has been but little investigated, there is sufficient evidence for constituting a special class of compound celluloses under this term, pecto-cellulose, having properties indicated in the type selected above.
In addition to pectic acid there exists in, or can readily be obtained from certain plants, a series of bodies of a similar nature, such as pectose, pectin, parapectic acid and metapectic acid. The most important of these are pectic acid and metapectic acid.
Pectic acid, though it rarely exists ready-formed in the plant, can readily be obtained from it by the action of weak alkalis. It is best procured by boiling the pulp of turnips with a 10 per cent. solution of sodium carbonate for about half an hour. If an acid be added to the filtered liquid, pectic acid is precipitated as a transparent colourless jelly, which {29} dries up to a transparent horny mass. By the prolonged action of alkalis or acids, pectic acid is converted into metapectic acid (C8H14O9), which may be obtained as a syrupy, strongly acid liquid.
From what we know of the properties of the members of the pectic group, and therefore of the pecto-celluloses, it will be readily seen that the latter are very liable under the action of alkalis to undergo conversion into soluble derivatives.
Conversely, a study of the action of alkalis upon plant substances, enables us to determine to what extent the latter partake of the nature of the pecto-cellulose, the importance of which to the practical paper maker we need hardly point out. For a further development of this idea (see p. [43]).
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