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112
PAPER AND ITS USES


sometimes in bleaching coloured papers in lines. Torn paper shows hurried sorting, as it is not difficult to see such a fault when turning over the sheets. In various coated papers sheets with uneven coating or surface markings should not be included as "good" paper. A paper which is even in texture cannot be considered matched by a supply which is "wild" or cloudy in the look-through. Although wildness is sometimes accompanied by strength in paper, this is not always so, and it is desirable that printing papers should not be wild.

To analyse papers in order to discover chemical residues and to identify them requires some very delicate tests, and unless one has had an extensive chemical training, mistaken conclusions may result.



The various apparatus and chemicals necessary for paper testing as detailed in this chapter (other than machines, chemical balance and microscope) are detailed below.

1 glass measure, 50 c.c. capacity.
2 beakers, 225 c.c.
6 beakers, 60 c.c.
1 dozen test tubes, 5 in. x ⅝ in.
1 test-tube stand to take 6 tubes.
6 porcelain crucibles without covers, No. 1.
1 tripod stand, 7 in. x 5 in.
1 piece gauze asbestos covered.
1 pipeclay triangle.
1 Bunsen burner 3 ft. rubber tubing

or one spirit lamp, 70 c.c

2 dozen glass slips, 3 in. x 1 in.
½ oz. cover glasses, No. 3, ⅝ in. diameter.
2 teasing needles.
1 oz. tannic acid.
1 oz. aniline sulphate.
1 oz. caustic soda.
5 oz. rectified spirit.
25 c.c. iodine in potass. Iodide sol.
25 c.c. sulphuric acid and glycerine sol.
25 c.c. phloroglucine solution.


Messrs Townson & Mercer Ltd., of 34 Camomile Street, London, E.C., undertake to supply the whole of the articles for 17s. 6d. if the Bunsen burner is desired, and for 16s. if a spirit lamp is to be used.