According to the account of Kiclaner, the disintegration of wood may be effected in the following four ways:
1. By heating direct in boilers at a pressure of 10 atmospheres. (See Dresel and Rosehain.)
2. In vertical boilers heated direct or by steam, and kept at a pressure of from 10 to 14 atmospheres. (Sinclair, Nicol, and Behrend.)
3. In revolving boilers, maintained at a pressure of 12 atmospheres by direct steam.
4. By means of a series of small vessels communicating with each other, and through which a lye circulates at a pressure of six atmospheres. (Ungerer.)
This latter process is preferable to the others.
Researches have also been made by the author in order to ascertain the loss which wood and cellulose suffer at different temperatures or in contact with varying quantities of alkali (NaHO).
The following is a resumé of the experiments, giving the loss in per cent, resulting from a "cooking" of three hours duration:
| I. | Ordinary pressure: | ||||
| 10 grms. cellulose, with 580 c.c. of caustic soda solution, sp. gr. 1.09 | 21.99 | ||||
| 10 | grms. of | soft | wood, treated as above | 49.19 | |
| 10 | " | hard | " | 53.68 | |
| II. | Pressure of five atmospheres: | ||||
| 10 grms. cellulose, with 500 c.c. caustic soda solution of sp. gr. 1.099 | 58.02 | ||||
| 10 | grms. of | soft | wood, treated as above | 75.85 | |
| 10 | " | hard | " | 69.80 | |
| III. | Pressure of ten atmospheres: | ||||
| 10 | grms. | of cellulose | 58.99 | ||
| 10 | " | soft | wood | 81.80 | |
| 10 | " | hard | " | 70.39 | |
| IV. | Ordinary pressure: | ||||
| 10 grms. of cellulose, with 500 c.c. caustic soda solution of sp. gr. 1.162 | 21.88 | ||||
| 10 | grms. of | soft | wood | 35.45 | |
| 10 | " | hard | " | 46.43 | |
| V. | Pressure of five atmospheres: | ||||
| 10 grms. of cellulose, with 500 c.c. caustic soda solution of sp. gr. 1.162 | 77.33 | ||||
| 10 | grms. of | soft | wood | 97.13 | |
| 10 | " | hard | " | 91.48 | |
| VI. | Ordinary pressure: | ||||
| 10 grms. of cellulose, with 500 c.c. caustic soda solution of sp. gr. 1.043 | 12.07 | ||||
| 10 | grms. of | soft | wood | 28.37 | |
| 10 | " | hard | " | 30.25 | |
| VII. | Pressure of five atmospheres: | ||||
| 10 grms. of cellulose, with 500 c.c. of caustic soda solution of sp. gr. 1.043 | 15.36 | ||||
| 10 | grms. of | soft | wood | 50.96 | |
| 10 | " | hard | " | 55.66 | |
| VIII. | Pressure of ten atmospheres: | ||||
| 10 grms. of cellulose, with 200 c.c. caustic soda solution of sp. gr. 1.043 | 20.28 | ||||
| 10 | grms. of | soft | wood | 70.31 | |
| 10 | " | hard | " | 65.59 | |
From this it is evident that by increasing the temperature and pressure the solvent action of the alkali is increased, but the strength of the lye exercises an influence which is even more marked. Thus, at a pressure of five atmospheres, the loss of cellulose was 0.75 with a caustic lye containing 14 per cent. of NaHO, while it was only 0.05 with a lye of 8 per cent. NaHO.