According to Franke, the constituents of stick-lac are, resin, 65.7 ; substance of the lac, 23.2; coloring matter, 0.6.
Seed-lac. When the resinous concre tion is taken off the twigs, coarsely pound ed, and triturated with water in a mortar, the greater part of the coloring matter is dissolved, and the granular portion which remains, being dried in the sun, consti tutes seed-lac. It contains, of course, less coloring matter than the stick-lae, and is much less soluble. John found in 100 parts of it, resin, 661 ; 1.7; matter of the lac, 16/ ; bitter balsamic matter, 2.5 ; coloring matter, 3.9 ; dun yellow ex tract, 0.4; envelopes of insects, 2.1 • lac de acid, 0-0; salts of potash and lime, 1.0; earths, 6.6; loss, 4.2.
In India the seed-lac is put into oblong bags of cotton cloth, which are held over a charcoal fire by a man at each end, and, as soon as it begins to melt, the bag is twisted so as to strain the liquefied resin through its substance, and to make it drop upon smooth stems of the banyan tree. In this way, the resin spreads into thin plates, and constitutes the substance known in commerce by the name of shellac.
The Pegu stick-lac, being very dark colored,-furnishes a shellac of a corres ponding deep hue, and therefore of nor value. The palest and finest shel lac is brought from the northern arms. It contains very little coloring matter. A stick-lac of an intermediate kind from the Mysore country, which yields a brilliant lao-dye and a good shellac.
Lac-dye is the watery infusion of the ground stick-lee, evaporated to dryness, and formed into cakes about two inches square, and half an inch thick. Dr. John found it to consist of coloring matter, 50; resin, 25; and solid matter, composed of alumina, plaster, chalk, and sand, 22.
Dr. Macleod, of Madras, prepared a very superior lac-dye from stick-lack, by digesting it in the cold in a slightly alka line decoction of the dried leaves of the enu3cylon tinotorium. This solution be ing used along with a mordant, consist ing of a saturated solution of tin in muri atic acid, was found to dye woollen cloth of a very brilliant scarlet line.
The cakes of lao-dye imported from In dia, stamped with peculiar marks to de signate their different manufacturers, are now employed exclusively in England for dyeing scarlet cloth, and are found to yield an equally brilliant color, and one less easily affected by perspiration than that prod.uced by cochineal. When the lac-dye was first introduced. sulphuric acid was the solvent applied to the pul verized cakes, but as muriatie acid has been found to answer so much better, it has entirely supplanted it. A good sol vent (No. 1) for this dye-stuff may be prepared by dissolving three pounds of tin in 60 pounds of muriatic acid, of spe cific gravity 1.19. The proper mordant for the cloth is made by mixing 27 pounds of muriatic acid of sp. gray. 1.17, with It pounds of nitric acid of 1.19; putting this mixture into a salt-glazed stone bot tle, and adding to it, in small bits at a time, grain tin, till 4 pounds be dissolved. This solution (No. 2) may be used with in twelve hours after it is made, pro vided it has become cold and clear. For dyeing, three quarters of a pint of the solvent (No 1) is to be poured upon each pound of the pulverized lao-dye, and al lowed to digest upon it for six hours. The cloth, befbre being subjected to the dye bath, must be scoured in the mill with fullers' earth. To dye 100 pounds
of pelisse cloth, a tin boiler of 300 gallons capacity should be filled nearly brimful with water, and a fire kindled under it. Whenever the temperature rises to 150° Fahr., a handful of bran and half a pint of the solution of tin (No. 2) are to be introduced. The froth, which rises as it approaches ebullition, must be skimmed off ; and when the liquor boils, 104 pounds of lac-dye, previously mixed with 7 pints of the solvent No. 1, and 84 pounds of solution of tin No. 2, must be poured in. An instant afterwards, 104 pounds of tartar, and 4 pounds of ground sumach, both tied up in a linen bag, are to be suspended in the boiling bath for five minutes. The fire being now with drawn, 20 gallons of cold water, with 101 pints of solution of tin, being poured into the bath, the cloth is to be immersed in it, moved about rapidly during ten mi nutes; the fire is to be then rekindled, and the cloth winced more slowly through the bath, which must be made to boil as quickly as possible, and maintained at that pitch for an hour. The cloth is to be next washed in the river; and lastly, with water only, in the fulling mill. The above proportions of the ingredients pro duce a brilliant scarlet tint, with a slight ly purple cast. If a more orange hue be wanted, white Florence argal may be used, instead of tartar, and some more sumach. Lac-dye may be substituted for cochineal in the orange-searlets; but for the more delicate pink shades, it does not answer so well, as the lustre is apt to be impaired by the large quantity of acid necessary to dissolve the coloring matter of the lac.
Mellas, by Mr. Hatched's analysis, consists of resin, 90-5 ; coloring matter, 0.5; wax, 4.0; gluten, 2.8; loss, 1.8; in 100 parts.
The resin may be obtained pure by treating shellac with cold alcohol, filtering the solution in order to separate a yellow gray pulverulent matter. When the alcohol Is again distilled off, a brown, translucent, hard, and brittle resin, of specific gravity 1•189, remains. It melts into a viscid mass with heat, and diffuses an aromatic odor. Anhydrous alcohol dissolves it in all proportions. Accord ing to John, it consists of two resins, one of which dissolves readily in alcohol, ether, the volatile and fat oils; while the other is little soluble in cold alcohol, and is insoluble in ether and the volatile oils. Unverdorben, however, bus detected no less than four different resins, and some other substances, in shellac. Shellac dis solves with case in dilute muriatic and acetic acids ; but not in concentrated sul phuric acid. The resin of shellac has a great tendency to combine with salifiable basses; as with caustic potash, which it deprives of its alkaline taste.
This solution, which is of a dark red color, dries into a brilliant, transparent, reddish-brown mass ; which may he re dissolved in both water and alcohol. By passing chlorine in excess through the dark-colored alkaline solution, the lee resin is precipitated in a colorless state. When this precipitate is washed and dried, it forms, with alcohol, an excellent pale-yellow varnish, especially with the addition of a little turpentine* and mastic.
With the aid of heat, shellac dissolves readily in a solution of borax.