Info

a = slow distillation. b = fast distillation.

a = slow distillation. b = fast distillation.

We have no such complete figures for the alcohol and acid yields from softwoods, but the general rule is that the yields of these products are very much lower, so low in fact that there is not much interest in determining the exact figures. Douglas fir lias been shown to give about .69 per cent alcohol and 1.5 per cent acetic acid when distilled in semi-commercial apparatus.14 The figures in Table 10 taken from Senfft10 are not comparable with those in the previous tables because they were obtained under" different conditions of distillation, but they show the relative values of hardwoods and softwoods for acetic acid production.

Moisture Content of Wood

Moisture occurs in wood in at least two different forms: (1) the water occurring as such between the fibres of the wood and (2) the water adsorbed in the ligno-cellulose. The water occurring between the wood fibres acts like any other free water and evaporates into unsaturated air until it is all removed. The adsorbed water, however, is decreased in vapor pressure and there is a definite equilibrium between the amount of adsorbed water, the temperature, and the humidity of the air with which it is in contact. This equilibrium relation between moisture in wood and the humidity of the air is shown for u Computed from resulta of Hunt, West Coast Lumberman, 1915, assuming the wood used to contain 15 per cent moisture.

three different temperatures in Figure io.lfl This figure shows, for example, that wood in contact with air of 50 per cent humidity at 700 F. can not be dried below about 9 per cent moisture content. It shows also why "air dried" wood may vary from 5 to 25 per cent moisture depending on the temperature and humidity of the air.

0 0

Post a comment