The methods of textile chemistry; by Dannerth Frederic 1881-

Author:Dannerth, Frederic, 1881- [from old catalog]
Language: eng
Format: epub
Tags: Textile industry and fabrics. [from old catalog], Chemistry, Technical
Publisher: New York, J. Wiley & sons; [etc., etc.]
Published: 1908-03-25T05:00:00+00:00

her dismay that the goods appear rotten after the first washing.

The formation of the oxycellulose is generally caused by undue exposure of the goods to light and air after removal from the bleach bath; then again it may result from the use of very strong bleach baths, but the chemical change which takes place is in both cases an oxidation. The test usually recommended to determine the presence of this oxidation product depends upon its affinity for the basic coloring matters. Five grams of methylene blue are dissolved in iooo grams of boiling water. The previously moistened fabric is now immersed in this for about ten minutes and then washed. The presence of oxycellulose in the fabric is indicated by spots or stripes which have been dyed a bright blue, while the rest is only slightly tinged. This test, though apparently simple, requires some experience if the results obtained are to be properly interpreted.

Another excellent test is carried out as follows: Boil the fabric thoroughly in water in order to remove any finishing material. Then squeeze and boil for five minutes in a mixture of 30 c.c. of Fehling's solution and 20 c.c. of water. A red color on the fabric due to the deposited cuprous oxide (Cu 2 0) indicates the presence of oxidized cellulose. This latter oxidation product may be prepared artificially by saturating a fabric with bleach solution and then exposing in an atmosphere of carbon dioxide.

7. In order to obtain a purer white and to remove the excess of chlorine from the fiber the goods are passed through the acid bath. As this treatment with muriatic acid often leaves the goods harsh many bleachers prefer to use sodium hyposulphite (Na2S 2 Og) or sodium bisul-

COTTON BLEACHING. PRODUCTS I OS

phite (NaHSOg) to insure a "soft feel." If used in sufficient quantity these substances effectually remove the chlorine which remains in the goods after the bleach bath, according to the following reactions:

2 Na^O, + 2 CI = 2 NaCl + Na^O,. NaHS0 3 + 2 CI + H 2 0 = 2 HC1 + NaHS0 4 .

To determine whether all the chlorine has been removed the washed fabric is immersed in a io per cent solution of potassium iodide to which a few drops of boiled starch solution have been added. The appearance of a blue color indicates the presence of free chlorine. This in turn shows that an insufficient quantity of " antichlor " has been used.

8. The presence of free mineral acid in cotton goods which are to be exposed to high temperatures is extremely detrimental to the strength of the fabric. The goods may be tested by moistening with a few drops of a yellow solution of methyl orange. Free acid will turn the color to red.

9. The detection of the presence of lime and of resin spots in a lot of goods is especially important in case they are to be afterward dyed with alizarine colors. The best test is to dye a 10-gram

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