| 摘要 |
400,974. Sulphite digestion of wood. DREYFUS, H., 22, Hanover Square, London. March 4, 1932, No. 6540. [Class 96.] Throughout the digestion of wood is used an aqueous solution or solutions of bisulphite with little or no free sulphur dioxide. The rates of free to combined sulphur dioxide may be 1 : 2, 10, or 50, &c., using a 2-8 per cent solution of bisulphite of sodium, potassium, calcium, magnesium, &c. Heating, e.g. to 110-160‹ C.. may be by direct or indirect high pressure steam, and the pressure may be 3-20 or over 100 atmospheres with or without inert gases or vapours, and the digestion may take 1-24 hours. The wood may be impregnated under pressure at about 50-100‹ C. and wetting agents. e.g. Turkey red oil may be used. In an example, spruce chips are heated at 140‹ C. and 10 atmospheres pressure for 8 hours in a solution of 6 per cent alkali metal bisulphite and 0.2 per cent free sulphur dioxide, nitrogen being forced into the digester.
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