Elastic.—Bisulphide of carbon, 4 oz.; indiarubber in fine shreds, 1 oz.; isinglass, 2 drachms ; guttapercha, oz.; dissolve. Used for joining leather or indiarnbber. The pai ts rnust be thinly coated with the solution, which is left for a few minutes to dry, and then heated to melting; the parts are placed in close contact, and the air-bubbles are well hammered out.
Eltctrical or Chemical Apparatus, for.—(a) A good cement for connecting the parts of chemical or electrical apparatus may be made by mixing 5 lb. rosin, 1 lb. wax, 1 lb. red ochre, and 2 oz. plaster of Paris, and melting the whole with moderate heat. (b) Black rosin, 7 lb.; red ochre, 1 lb.; plaster of Paris, ,1 lb., well dried, and added while warm; then heated to a little above 100° (212° F.), and agitated together, till all frothing ceases and the liquid rnns smooth ; the vessel is then removed from the fire, and the contents are stirred till sufficiently cool for use.
Grinders'.—(a) Pitch, 5 parts ; wood ashes, 1 part ; hard tallow, 1 part ; melted together. (b) Black rosin, 4 lb.; beeswax, 1 lb. ; melted ; to these is added whiting, previously madc red hot, and while still warm, 1 lb. These are used for fixing pieces of glass, &a., while grinding. (c) Shellac, melted, and applied to the pieces slightly warmed. Used for lenses and fine work.
Gun:I.—An aqueous solution of gum arable and gum tragacanth gives a good cement which will keep for a long time.
Impervious.—An impervious cement for apparatus, corks, &c., may be made by rubbing up zinc white with copal varnish ; this is applied and left to dry, then covered with the same material mixed thinner, and lastly with copal varnish alone.
Indianite.—(a) Finely-chopped indiarnhber, 100 parts; rosin, 15 parts ; shellac, 10 parts ; dis solved in a sufficient quantity of bisulphide of carbon ; (b) indiarubber, 15 grs. ; chloroform, 2 oz.; maatic, i oz. ; the first and second ingredients are mixed, and, when the rubber is dissolved, the mastic is added in powder, and the whole is left to macerate for a week. These cements are used for uniting pieces of indiarubber.
Indiarubber.—(a) 'Virgin or native indiarubber is cut with a wet knife into the thinnest possible slices, which are then divided by shears into threads as fine as small twine. A small quantity of
the shreds (say A of the capacity of tbe bottle) are then put into a wide-mouthed bottle, and the latter is three-fourths filled with benzine of good quality, and perfectly free from oil. The rubber almost immediately commences to swell, and in a few days, if often shaken, it will assume the con sistence of honey. Should it be inclined to remain in undissolved lumps, more benzine must be added ; thinness may be corrected by adding more indiarubber. A piece of solid rubber no larger than a walnut will make a pint of the cement. It dries in a few minutes, and, by using three coats in the usual planner, leather straps, patches, rubber soles, backs of books, &c., may be joined with great firmness. (b) Indiarnbber, 8 grms ; chloroform, 600 grms. ; mastic resin, 150 grms.; the india rubber is dissolved in the chloroform, the mastic is added, and the whole is left to macerate for eight days, that being the time necessary for the solution of the mastic. The cement is applied cold on a brush, and is used for joining glass. (c) Very finely-divided indiarubber is melted at a temperature of 200° (392° F.); as soon as fusion commences, one-fifteenth the quantity of tallow or wax is added, taking care to watch the heat and to stir without eeasing. Wben the mass is com pletely melts& lime, slaked and sifted, is added in small instalments, till it amounts to half the qua.ntity of the indiarubber. The cement thus obtained is soft; if the proportion of lime be doubled, the cement will be harder, but still supple. When the compound bas acquired a suitable con sistence, the fire is withdrawn, and the preparation is finished. This forms a good cement for he: metically sealing vessels. It does not dry, and remains for a long time ductile and tenacious; but it may be made to harden, if necessary, by adding 1 part of red-lead to the quantities indicated above.
Ivory, or Mother-of-Pearl, for.—Isinglass, 1 part, and white glue, 2 parts ; dissolved in water, 30 parts; the solution is filtered, and evaporated down to 6 parts; to this is added gum mastic, -51-, part, dissolved in alcohol, part ; and zinc wbite, 1 part. When required for use, it is warmed and shaken up.