CALENDER 573 



'frequently deposited upon shells, moss, and other plants, which it covers with a cal- 

 careous crust, producing frequently a perfect representation in stone of the substance 

 so enveloped. H. W. B. 



CALCEDONY. See CHALCEDONY. 



CALCEDONYX. See CHALCEDONYX. 



CALCINATION (from Calcine). The operation of expelling from a substance, 

 by heat, either -water or volatile water combined with it. Thus, the process of burn- 

 ing lime, to expel the carbonic acid, is one of calcination. The result of exposing the 

 carbonate of magnesia to heat, and the removal of its carbonic acid, is the production 

 of calcined magnesia. The term was, by the earlier chemists, applied only -when the 

 substance exposed to heat was reduced to a cate, or to a friable powder, this being 

 frequently the oxide of a metal. It is now, however, used when any body is subjected 

 even to a process of roasting. 



CALCIPHYRE. A name given by Brongniart to a compound of granular lime- 

 stone with garnet or felspar, usually porphyritic. 



C AXiCITE. Crystallised carbonate of lime. See ICELAND SPAR. 



CALCIUM (Symbol, Ca. ; Atomic weight, 20.) The metal contained in the oxide 

 well known as lime. It was first obtained by Davy, in 1808, by the electrolysis of the 

 hydrate, carbonate, chloride, or nitrate of lime. Matthiessen obtained it by heating, 

 in a porcelain crucible, a mixture of two atoms of chloride of calcium with one of chlo- 

 ride of strontium, and a small quantity of chloride of ammonium, until the latter is 

 volatilised. The current from six cells of Bunsen's battery is then sent through the 

 mixture by a charcoal pole of as large size as possible, and a piece of iron pianoforte 

 wire (No. 6), not more than two lines in length, which is united -with the negative 

 pole of the battery by means of a stronger line reaching close to the surface. A small 

 crust is to be formed round the wire at the surface. To collect the small globules 

 deposited on the wire, the latter must be taken out every two or three minutes, 

 together with the crust. The globules are crushed in a mortar, and the flattened 

 granules are then picked out. Calcium is a brilliant pale yellow metal, malleable 

 and ductile. See LIME. 



CALCIUM, CHLORIDE OF. Ca Cl (CaCl 2 ). A deliquescent salt readily 

 obtained by dissolving chalk in hydrochloric acid. A saturated solution boils at 355 F., 

 and is therefore sometimes employed as a bath where such a temperature is required. 

 The hydrated chloride, obtained by evaporation of the solution, causes great depression 

 of temperature -when dissolved in -water ; hence its use in certain freezing mixtures. 

 Mercury may be frozen by means of a mixture of crystallised chloride of calcium and 

 snow. The anhydrous salt obtained by heating the: hydrate, is extremely deliquescent, 

 and is therefore used as a desiccating agent. After exposure to sunlight, the chloride 

 appears luminous in the dark, and was formerly called Homberg's Phosphorus. 



CALCIUM!, FLUORIDE OP. CaF (CaP 2 ). This salt occurs in the bones 

 and teeth of animals, and in minute quantity in sea-water, and in the water of certain 

 springs. It is found native as Fluor Spar. 



CALCIUM, OXIDE OF. See LIME. 



CALCIUM, PHOSPHIDE OF. By distilling phosphorus over lime at a low 

 red heat, an impure phosphide of calcium is obtained. This salt, when thrown into 

 water, evolves phosphuretted hydrogen, which is spontaneously imflammable. After 

 the phosphide has been slaked, by exposure to a moist atmosphere, it also yields 

 phosphuretted hydrogen when brought in contact with water, but the gas thus ob- 

 tained does not ignite spontaneously. 



CALCIUM, SULPHIDES OF. Several sulphides of calcium are known, but 

 are of no importance in the arts. Canton's Phosphorus is an impure sulphide, ob- 

 tained by calcining oyster-shells, and heating the product with one-third of its weight 

 of flowers of sulphur, in a closed crucible. 



CALC-SINTER. The incrustations of carbonate of lime upon the ground, or the 

 pendulous conical pieces called stalactites, attached to the roofs of caverns, are so 

 called. 



CALC-SP AR. Crystallised carbonate of lime or calcite. 



CALCULUS. The stony-looking morbid concretion occasionally formed in the 

 bladders and other parts of living animals. Its examination belongs to medical 

 chemistry. 



CALEMBEG. An ornamental wood ; it is often called aloes wood, and some- 

 times green sandal-wood, being of a greenish colour, and slightly scented. 



CALEMBERRX. A name sometimes given to coromandel wood. See COROMAN- 

 DEL WOOD. 



CALENDER (Calandrc, Fr. ; Kalender, Ger.), a word derived from the Greek 

 Kv\tvSpos ' cylinder,' is the name of a machine consisting of two or more cylinders 

 revolving so nearly in contact with each other, that cloth passed through between 



