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CEMENTS.

CEDRA ( Cedrai , Fr.) is the fruit of a species of orange, citron, or lemon, a tree whichbears the same name. Its peel is very thick, and covered with an epidermis which en-closes a very fragrant and highly prized essential oil. The preserves flavored with itare very agreeable. The citrons are cut into quarters for the dry comfits, but are put wholeinto the liquid ones. The liquorisl-perfumer makes with the peel of the cedra an ex-cellent liqueur; for which purpose, he plucks them before they are quite ripe; gratesdown the peel into a little brandy, or cuts them into slices, and infuses these in thespirits. This infusion is distilled for making perfume; but the flavor is better whenthe infusion itself is used. See Essences, Liq.uoiust, Perfumery .

CELESTINE. Native sulphate of strontia, found abundantly near Bristol, in thered marl formation. It is decomposed, by ignition with charcoal, into sulphuret ofstrontia, which is converted into nitrate by saturation with nitric acid, evaporation, andcrystallization. This nitrate is employed for the production of the red light in theatricalfire-works.

CEMENTATION. A chemical process, which consists in imbedding a solidbody in a pulverulent matter, and exposing both to ignition in an earthen or metalliccase. In this way, iron is cemented with charcoal to form steel, arid bottle glass withgypsum powder, or sand, to form Reaumur’s porcelain.

CEMENTS . ( aments , Fr.; Cdmcnle , Kit/e, Germ.) Substances capable of taking theliquid form, and of being in that state applied between the surfaces of two bodies, so as tounite them by solidifying. They may be divided into two classes, those which are appliedthrough the agency of a liquid menstruum, such as water, alcohol, or oil, and those whichare applied by fusion with heat.

The diamond cement for uniting broken pieces of china, glass, &c., which is sold as asecret at an absurdly dear price, is composed of isi»glass soaked in water till it becomessoft, and then dissolved in proof spirit, to which a little gum resin, ammoniac, or galba-num, and resin mastic are added, each previously dissolved in a minimum of alcohol-When to be applied, it must be gently heated to liquefy it; and it should be kept foruse in a well-corked vial. A glass stopper would be apt to fix so as not to be remove'able. This is the cement employed by the Armenian jewellers in Turkey for glue-ing the ornamental stones to trinkets of various kinds. When well made it resistsmoisture.

Shellac dissolved in alcohol, or in a solution of borax, forms a pretty good cemenbWhite of egg alone, or mixed with finely sifted quicklime, will answer for unitingobjects which are not exposed to moisture. The latter combination is very strong, an^-is much employed for joining pieces of spar and marble ornaments. A similar coiri'position is used by copper-smiths to secure the edges and rivets of boilers; only bullocksblood is the albuminous matter used instead of white of egg. Another cement in whichan analogous substance, the curd or caseum of milk is employed, is made by boil* 1 ^slices of skim-milk cheeses into a gluey consistence in a great quantity of water, andthen incorporating it with quicklime on a slab with a muller, or in a marble mor* ar 'When this compound is applied warm to broken edges of stoneware, it unites them veryfirmly after it is cold.

A cement which gradually indurates to a stony consistence may be made by mi* 1 ”*20 parts of clean river sand, two of litharge, and one of quicklime, into a thin putt?with linseed oil. The quicklime may he replaced with litharge. When this cementapplied to mend broken pieces of stone, as steps of stairs, it acquires after some tuncstony hardness. A similar composition has been applied to coat over brick walls, undthe name of mastic. *

The iron-rust cement is made of from 50 to 100 parts of iron borings, pounded ansifted, mixed with one part of sal-ammoniac, and when it is to be applied moistened wias much water as will give it a pasty consistency. Formerly flowers of sulphur wereus vand much more sal-ammoniac in making this cement, but with decided disadvantage? "the union is effected by the oxydizement, consequent expansion and solidification of ^iron powder, and any heterogeneous matter obstructs the effect. The best proportionsal-ammoniac is, I believe, one per cent, of the iron borings. Another composition oi > ssame kind is made by mixing 4 parts of fine borings or filings of iron, 2 parts of p® 1 ^

clay, and 1 part of pounded potsherds, and making them into a paste with salt ^water. When this cement is allowed to concrete slowly on iron joints, it becomes vnard. j 0 f

For making architectural ornaments in relief, a moulding composition ischalk, glue, and paper paste. Even statues have been made with it, the paper aidm=,cohesion of the mass. . . . heal

Mastics of a resinous or bituminous nature which must be softened or fusedrre the following: — . . j by a

Mr. S. Varley’s consists of sixteen parts of whiting sifted and thoroughly ant > ^

rsd heat, adding when cold a melted mixture of 16 parts of black rosin and 1 ot beeand stirring well during the cooling.