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Updated: September 22, 2025
A piece of wool similarly worked in the bath is also dyed. However, the unfortunate circumstance is that this colour is fast neither to light nor alkalis. Contact with soap and water, even, turns the yellow-dyed cotton, reddish-brown.
His Researches, Chemical, and Philosophical , led to his appointment as Director of the Chemical Laboratory at the Royal Institution, where he also delivered courses of scientific lectures with extraordinary popularity. Thereafter his life was a succession of scientific triumphs and honours. His great discovery was that of the metallic bases of the earths and alkalis.
This unity, although a mere idea, thinkers have found it necessary rather to moderate the desire than to encourage it. It was considered a great step when chemists were able to reduce all salts to two main genera acids and alkalis; and they regard this difference as itself a mere variety, or different manifestation of one and the same fundamental material.
The yellow compound it contains is called "Orellin," and it also contains an orange compound called "Bixin," which is insoluble in water, but readily soluble in alkalis and in alcohol with a deep yellow colour. To dye cotton with it, a solution is made of the colour in a boiling solution of carbonate of soda. The cotton is worked in the diluted alkaline solution whilst hot.
In the next case the series of Oxides begins. Herein are the oxides and hydrous oxides of manganese. Having examined the sulphurets and oxides, the visitor should cross to the northern suite of tables marked from 48 to 54. Here are arranged a series of the Carbonates, or combinations of carbonic acid with earths, metallic oxides or alkalis.
Soap-boiling is not so easy as may be imagined; it requires not only much attention, but the quality is dependent upon the proper mixture of the alkalis. Sixty parts of potash and forty of lime are, I believe, the proportions for common soap. I had neither lime nor potash, but I shortly procured both.
But whereas caustic alkalis have not much effect on vegetable fibres, if kept out of contact with the air, the animal fibres are very quickly attacked. Superheated steam alone has but little effect on cotton or vegetable fibres, but it would fuse or melt wool.
Alkalis have a very considerable action on fur and wool, but the effects vary a good deal according to the kind of alkali used, the strength and the temperature of the solution, as also, of course, the length of period of contact. The caustic alkalis, potash and soda, under all conditions affect wool and fur injuriously.
They are mostly solid, glassy-looking substances insoluble in water, but soluble in alcohol and wood spirit. In many cases the alcoholic solutions show an acid reaction. The resins are partly soluble in alkalis, with formation of a kind of alkali salts which we may call resin-soaps.
By means of water one can discover what acids, alkalis, or salts the parts of the paper with colored borders or white spots contain. With the aid of a pipette cover these spots with water and let it remain for ten or fifteen minutes; then with the pipette remove the liquid and examine the products it holds in solution.
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