34

DYEING AND CALICO PRINTING.

Cotton-Wax.

There can be no doubt that this substance must be classed with the waxes,bodies which are distinguished by their insolubility in water and alkalineliquids, their sparing solubility in alcohol and ether, and their high melting-point. Indeed it so closely resembles in many respedts the better knownvegetable waxes, such as the cerosine prepared by Avequin from the leaves ofthe sugar-cane, and the wax from the leaves of the Carnauba palm (Coryfhacerifera ), examined by Brande* and Lewyf, that its identity with one of thesemay be suspedted. It has the following properties :—

It is insoluble in water, but soluble in alcohol and ether. If a concentratedsolution in boiling alcohol be allowed to cool, the greatest part of the substanceis deposited, causing the liquid to assume the appearance of a thick whitejelly, like starch-paste, which, when examined under the microscope, is foundto consist of minute scales and needles suspended in the alcoholic liquid.When the mass is filtered off and dried, it shrinks very much, and is convertedinto a coherent cake, which has a waxy lustre, is translucent, friable, and'lighter than water, and does not soften when kneaded between the fingers.A specimen of the substance from East Indian cotton, when heated in the usualmanner in a capillary tube, was found to melt at 86° C. to a transparentliquid, which solidified again at 8i° C. Another specimen, from Americancotton, fused at 86°, and became solid again at 82° C. According to Avequin,cerosine fuses at 82° and solidifies at 8o°. Carnauba wax, according to Lewy,melts at 83*5. When heated on platinum foil, cotton-wax gives off an odourresembling that of burning fat, and then burns with a bright flame, withoutleaving any ash. If heated in a tube, it melts, emits a penetrating odour, andthen volatilises completely, yielding an oily sublimate, which soon becomessolid and crystalline and seems to consist of unchanged substance. Singularto say, cotton-wax, when pure, is quite insoluble in caustic alkalies; and it istherefore difficult to account for its presence among the products extra&edfrom cotton by soda-lye, unless it be assumed that it exists originally, notwithin the fibre, but on its surface, and is merely fused and mechanicallydetached by the adtion of the hot liquid. When treated with boiling dilutecaustic soda-lye, it melts without dissolving, and the filtered liquid gives onlya trifling precipitate with acid ; but when carefully heated with hydrate of soda,it yields a compound which is entirely soluble in water; and the solution nowgives, with acid, a copious white fiocculent precipitate, which consists of a truefatty acid, formed by a process similar to that of ordinary saponification, ormore so perhaps to that by which alcohols are converted into the correspondingacids. When cotton-wax is treated with fuming nitric acid, it does not dis-solve, even when the acid is boiled for some time ; it merely melts, andsolidifies on cooling. But a change has, nevertheless, taken place; for if theexcess of acid be poured off, and the undissolved fatty matter, after beingwashed, be treated with boiling caustic soda-lye, it dissolves entirely, and thesolution gives, with acid, a white fiocculent precipitate. By the a&ion ofnitric acid, therefore, the substance is probably transformed in the samemanner as by the adtion of dry caustic soda.

Jn order to prepare the substance for analysis, it was kept in a state of

* Philosophical Transactions for 1811, p.261.

+ Journ. f, Prakt. Chemie, B, xxxvi., S. 65.