Composition (Hugo Müller):—
| Cellulose | 64·07 |
|---|---|
| Fat and wax | ·62 |
| Aqueous extract | ·96 |
| Lignin and pectous substances | 21·60 |
| Water | 11·73 |
| Ash | 1·02 |
WOOD.
In America, however, poplar and other woods are largely employed. The coniferæ yield a larger proportion of pulp than most other woods, the individual fibres, moreover, are longer, and for these reasons it is generally preferred. On the other hand, however, poplar is more readily acted upon by reagents. Fig. 15 gives the microscopic appearance of {61} the fibre of the common white fir. It is characterised by the presence of numerous pitted vessels (Fig. a).
FIG. 15.
Pine wood consists essentially of a compound cellulose, resembling in most of its properties the jute fibre (see p. [16]). With iodine solution it gives a deep yellow colour. The chemical composition of some of the more important woods will be seen from the following analyses. (Müller.)
| Birch. | Beech. | Lime. | Pine. | Poplar. | |
|---|---|---|---|---|---|
| Cellulose[*] | 55·52 | 45·47 | 53·09 | 56·99 | 62·77 |
| Resin | 1·14 | 0·41 | 3·93 | 0·97 | 1·37 |
| Aqueous extract | 2·65 | 2·41 | 3·56 | 1·26 | 2·88 |
| Water | 12·48 | 12·57 | 10·10 | 13·87 | 12·10 |
| Lignin | 28·21 | 39·14 | 29·32 | 26·91 | 20·88 |
[*] For the amounts of cellulose actually obtained in practice see p. [77].
The above results are calculated on the ash-free wood. The ash varies from about 0·3 to 0·7 per cent.