The practical papermaker : a complete guide to the manufacture of paper / by James Dunbar.

  • Dunbar, James.
Date:
1887
Catalogue details

Licence: Public Domain Mark

Credit: The practical papermaker : a complete guide to the manufacture of paper / by James Dunbar. Source: Wellcome Collection.

    106/130 (page 94)
    tain half a grain of bleaching powder. Take one ounce of the arsenious solution, and add to it a little sulphate of indigo, sufficient to render it of a distinct blue colour; then into this pour slowly the bleach¬ ing liquor from the alkalimeter until the blue colour disappears, stirring continually during the operation. Note the number of graduations required to effect this change. Every 10 grams of the arsenious acid is equal to 7’2 grains of chlorine, so the quantity of bleaching liquor taken to decolour the indigo will contain that amount of chlorine. Suppose it has required 48 graduations of the bleaching liquor to effect the change, this will be equal to 24 grains of bleaching powder : therefore 24 grains of bleaching powder will contain 7*2 of chlorine; and if 24 contain 7*2, 100 will contain 30. The sample will therefore contain 30 per cent, of chlorine. EXAMINATION OF SODA AS TO ITS CAUSTICITY. The value of soda to the papermaker depends upon the amount of caustic alkali which it contains. The admixed salts contained in soda consist of various sorts, and are of no value to the paper- maker. As the proportion of these salts varies very much, it is necessary to examine the soda periodi¬ cally, to ascertain the quantity of caustic alkali it contains. This can be done very easily, and by a re-agent which is applicable to both caustic soda and soda ash. Caustic soda differs from soda ash in that its alkali (pure soda) is in a free and uncombined state, whilst the alkali of soda ash is united to an acid— carbonic acid. This acid, however, is but a weak body, and the test, which serves to ally with the caustic alkali in caustic soda, is of sufficient strength