1725. To Bleach Gutta Percha

1725.    To Bleach Gutta Percha. Dissolve 1 part gutta percha in 20 parts hot benzole, shake the solution with 1/10 part freshly calcined plaster, and set aside, with occasional agitation, for 2 days. The clear pale brownish-yellow liquid is then decanted into another vessel containing double its bulk of alcohol fortius {see No. 1439 (Stronger Alcohol)), when the gutta percha will be precipitated in the form of a brilliantly white tenacious mass, which is pounded together in a mortar, and rolled into cylindrical sticks.

1726. Bleaching Woolen Rags

1726.   Bleaching Woolen Rags. These are most effectually bleached by the application of sulphurous acid. Of course, in many instances, the color of the rags, supposing the same to be dyed or printed goods, will be also destroyed. Chlorine cannot be used for this purpose, because it causes woolen and silk fabrics to become yellow, and impairs the strength of the fibre, by entering into chemical combination with the wool, silk, and other similar substances of animal origin; as, for instance, sponge, animal gut, isinglass, etc., all of which, if requiring bleaching, are bleached by sulphurous acid.

1727. New Method of Bleaching Feathers

1727.      New Method of Bleaching Feathers. This process is an entirely newly-discovered one, whereby the feathers of ostriches and other birds may be bleached, even if these feathers are naturally black or dark gray colored. The feathers are placed for from 3 to 4 hours in a tepid dilute solution of bichromate of potassa, to which, cautiously, some nitric acid has been added. After this lapse of time the feathers will be found to have assumed a greenish hue, owing to the oxide of chromium precipitated on the substance ; in order to remove this, the feathers are placed in a dilute solution of sulphurous acid in water, whereby the feathers become perfectly white and bleached. Care is to be taken that the solution of bichromate be not made too strong, and especially that not too much nitric acid be used, which would cause an irremovable yellow color.

1728. Table Showing the Number of Parts of a Weak Bleaching Liquor

1728. Table Showing the Number of Parts of a Weak Bleaching Liquor, Required to be added to 1 Part Bleaching Liquor of 6° Twaddell, to Produce a Liquor of a given Strength. According to Mr. Crum, the strength of liquor for bleaching cotton should be less than 1° Twaddell; the following table enables an operator to increase the strength of a weak bleaching liquor with a great degree of accuracy. The left hand column gives the strength of the weak liquor, expressed in 1/12 parts of 1°. At the head of the other columns stands the degree of strength required, and under these headings will be found the number of parts of weak liquor required to be added to 1 part of a liquor of 6° Twaddell, to produce the required strength of the mixture. (See No. 68 (Twaddell's Hydrometer).)