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To Detect Cotton in Linen (Charcoal and give a strong)

The charcoal, and give a strong smell.

Decidedly the best and safest method, and one applicable in all cases, is a microscopic examination, by which not only the structure, but also the nature of the fibre can be demonstrated. Cotton, wool and silk are easily distinguished by the microscope, as they differ materially in appearance. Cotton forms flat, narrow ribbons, curled up in spirals like those of a corkscrew; wool fibre is stouter than all others, and may be recognized by its scaly surface, while silk is the thinnest fibre, has the smoothest surface, and possesses the least structure. These appearances are very characteristic, and any one who has observed them once will ever afterwards recognize them again at first sight. 301. To Distinguish Silk and Wool in a mixture with any other animal or vegetable Fabrics. Silk can always be identified in fibre by means of concentrated hydrochloric acid, which dissolves it completely and immediately, without appreciably affecting any woolen or woody fibre with which the silk may have been interwoven. Strong sulphuric acid has also a powerful solvent effect upon silk, and is likewise much more destructiveinitsaction upon cotton than the other acid. Should it be desired to determine the nature of any fibres remaining after the solution of piece to be tested should be boiled to remove the silk, it is first necessary to wash and colall dressing, and then dried; put a portion of lect them, when they will usually be found the piece into common vitriol for about one destitute of color. To decide whether wool minute; take it out and wash it in water sev- is present or absent, a solution of picric acid eral times, and then into a weak solution of may be employed, which instantly imparts a soda or potash, and all the gummy matter full yellow tint to the wool, but does not in formed is removed by gentle rubbing. By the least affect cotton, linen, or China grass; this process the cotton is dissolved and the so that it is only necessary to immerse the linen remains, or any portion of the cotton fabric in the dye, wring it out, and wash well that is not dissolved becomes opaque white, with water. Should any portion remain of a while the linen is transparent. By comparing yellow color, the presence of wool is indicated. the portion thus tested, with a similar portion Other methods can be employed similar in not tried, the quantity of cotton present can easily be estimated. principle, but the picric acid is believed to be best.

Discrimination between the different kinds of fibre can best be prosecuted by means of the microscope, but their quantity is best found by dissolving away one fibre, as already