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CADMIUM (symbol Cd, atomic weight 112...

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Originally appearing in Volume V04, Page 931 of the 1911 Encyclopedia Britannica.

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CADMIUM (symbol Cd, atomic weight 112.4 (0=16))

CADMIUM (See also:
SYMBOL (Gr. o-uµ(3oXov, a sign)
symbol Cd, atomic See also:
WEIGHT
weight 112.4 (0=16)) , a metallic See also:

ELEMENT (Lat. elementum)

element, showing a See also:

close relationship to See also:

ZINC

zinc, with which it is very frequently associated. It was discovered in 1817 by F. Stromeyer in a See also:

SAMPLE (through the O. Fr. essemple, from Lat. exemplum; a doublet of " example ")

sample of zinc carbonate from which a specimen of zinc See also:

OXIDE

oxide was obtained, having a yellow See also:

COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour, although quite See also:

FREE

free from See also:

IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron; Stromeyer showing that this coloration was due to the presence of the oxide of a new See also:

metal. Simultaneously See also:

Hermann, a See also:

German chemical manufacturer, discovered the new metal in a specimen of zinc oxide which had been thought to contain See also:

ARSENIC (symbol As, atomic weight 75.0)

arsenic, since it gave a yellow precipitate, in See also:

ACID (from the Lat. root ac-, sharp; acere, to be sour)

acid See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution, on the addition of sulphuretted See also:

HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen. This supposition was shown to be incorrect, and the nature of the new element was ascertained. Cadmium does not occur naturally in the uncombined See also:

CONDITION (Lat. condicio, from condicere, to agree upon, arrange; not connected with conditio, from condere, conditum, to put together)

condition, and only one See also:

MINERAL

mineral is known which contains it in any appreciable quantity, namely, See also:

GREENOCKITE

greenockite, or cadmium sulphide, found at See also:

GREENOCK

Greenock and at Bishopton in See also:

Scotland, and in Bohemia and See also:

Pennsylvania. It is, however, nearly always found associated with zinc See also:

BLENDE, or SPHALERITE

blende, and with See also:

CALAMINE

calamine, although only in small quantities. The metal is usually obtained from the flue-dust (produced during the first three or four See also:

HOURS, CANONICAL

hours working of a zinc See also:

DISTILLATION (from the Lat. distillare, more correctly destillare, to drop or trickle down)

distillation) which is collected in the See also:

SHEET

sheet iron cones or adapters of the zinc retorts. This is mixed with small See also:

COAL

coal, and when redistilled gives an enriched dust, and by repeating the See also:

PROCESS

process and distilling from See also:

CAST (from the verb meaning " to throw "; the word is Scand. in origin, cf. Dan. kaste, and Swed. kasta; " cast " in Middle Eng. took the place of the A.S. weor pan, cf. Ger. werf en)

cast iron retorts the metal is obtained. It can be purified by solution in hydrochloric acid and subsequent precipitation by metallic zinc. Cadmium is a See also:

white metal, possessing a bluish tinge, and is capable of taking a high See also:

POLISH

polish; on breaking, it shows a distinct fibrous fracture. By sublimation in a current of hydrogen it can be crystallized in the See also:

FORM (Lat. forma)

form of See also:

REGULAR

regular octahedra; it is slightly harder than See also:

TIN (Lat.- stannum, whence the chemical symbol " Sn "; atomic weight =117.6, 0=16)

tin, but is softer than zinc, and like tin, emits a crackling See also:

sound when See also:

bent.

It is malleable and can he rolled out into sheets. The specific gravity of the metal is 8.564, this value being slightly increased after hammering; its specific See also:

HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat is 0.0548 (R. See also:

Bunsen), it melts at 310-320° C. and boils between 763-772° C. (T. Carnelley), forming a deep yellow vapour. The cadmium See also:

MOLECULE (from mod. Lat. molecula, the diminutive of moles, a mass)

molecule, as shown by determinations of the See also:

DENSITY (Lat. densus, thick)

density of its vapour, is monatomic. The metal unites with the See also:

MAJORITY (Fr. majorite; Med. Lat. majoritas; Lat. major, greater)

majority of the heavy metals to form See also:

ALLOYS (through the Fr. aloyer, from Lat. alligare, to combine)

alloys; some of these, the so-called fusible alloys, find a useful application from the fact that they possess a See also:

low melting-point. It also See also:

TEETH (O.E. Eel); plural of tooth, O.E. top)

teeth. The metal is quite permanent in dry See also:

air, but in moist air it becomes coated with a superficial layer of the oxide; it See also:

burns on See also:

HEATING

heating to redness, forming a See also:

brown coloured oxide; and is readily soluble in mineral acids with formation of the corresponding salts. Cadmium vapour decomposes See also:

WATER

water at a red heat, with liberation of hydrogen, and formation of the oxide of the metal. Cadmium oxide, CdO, is a brown See also:

POWDER (through O. Fr. puldre, modern poudre, from Lat. pulvis, pulveris, dust)

powder of specific gravity 6.5, which can be prepared by heating the metal in air or in See also:

OXYGEN (symbol 0, atomic weight 16)

oxygen; or by ignition of the nitrate or carbonate; by heating the metal to a white heat in a current of oxygen it is obtained as a dark red crystalline sublimate. It does not melt at a white heat, and is easily reduced to the metal by heating in a current of hydrogen or with See also:

CARBON (symbol C, atomic weight 12)

carbon.

It is a basic oxide, dissolving readily in acids, with the formation of salts, somewhat analogous to those of zinc. Cadmium hydroxide, Cd(OH)2, is obtained as a white precipitate by adding See also:

POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]

potassium hydroxide to a solution of any soluble cadmium See also:

salt. It is decomposed by heat into the oxide and water, and is soluble in See also:

AMMONIA (NH3)

ammonia but not in excess of dilute potassium hydroxide; this latter See also:

PROPERTY

property serves to distinguish it from zinc hydroxide. The chloride,CdCl2,bromide,CdBr2,and iodide,Cdl2,arealsoknown, cadmium iodide being sometimes used in See also:

photography, as it is one of the few iodides which are soluble in See also:

ALCOHOL

alcohol. Cadmium chloride and iodide have been shown to behave in an anomalous way in aqueous solution (W. Hittorf, Pogg. See also:

Ann., 1859, 106, 513), probably owing to the formation of complex ions; the abnormal behaviour apparently diminishing as the solution becomes more and more dilute, until, at very high dilutions the salts are ionized in the normal manner. Cadmium sulphate, CdSO4, is known in several hydrated forms; being deposited, on spontaneous evaporation of a concentrated aqueous solution, in the form of large monosymmetric crystals of See also:

composition 3CdSO4.8H20, whilst a boiling saturated solution, to which concentrated sulphuric acid has been added, deposits crystals of composition CdSO4•H2O. It is largely used for the purpose of making See also:

standard electric cells, such for example as the See also:

WESTON, THOMAS (1737-1776)

Weston See also:

CELL (from Lat. cella, probably from an Indo-European kal —seen in Lat. celare, to hide; another suggestion connects the word with Lat. cera, wax, taking the original meaning to refer to the honeycomb)

cell. Cadmium sulphide, CdS, occurs naturally as greenockite (q.v.), and can be artificially prepared by passing sulphuretted hydrogen through acid solutions of soluble cadmium salts, when it is precipitated as a See also:

PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

pale yellow amorphous solid. It is used as a pigment (cadmium yellow), for it retains its colour in an See also:

ATMOSPHERE (Gr. fir µ6r, vapour; orkaipa, a sphere)

atmosphere containing sulphuretted hydrogen; it melts at a white heat, and on cooling solidifies to a See also:

lemon-yellow micaceous See also:

mass. Normal cadmium See also:

CARBONATES

carbonates are unknown, a white precipitate of variable composition being obtained on the addition of solutions of the alkaline carbonates to soluble cadmium salts.

Cadmium nitrate, Cd(NO3)2.4H20, is a deliquescent salt, which may be obtained by dissolving either the metal, or its oxide or carbonate in dilute nitric acid. It crystallizes in needles and is soluble in alcohol. Cadmium salts can be recognized by the brown incrustation which is formed when they are heated on See also:

CHARCOAL

charcoal in the oxidizing See also:

FLAME (Lat. flamma; the root flag- appears in flagrare, to burn, blaze, and Gr. d, XEryew)

flame of the See also:

BLOWPIPE

blowpipe; and also by the yellow precipitate formed when sulphuretted hydrogen is passed though their acidified solutions. This precipitate is insoluble in See also:

COLD (in O. Eng. cald and ceald, a word coming ultimately from a root cognate with the Lat. gelu, gelidus, and common in the Teutonic languages, which usually have two distinct forms for the substantive and the adjective, cf. Ger. Kolte, kalt, Dutch koude

cold dilute acids, in ammonium sulphide, and in solutions of the See also:

CAUSTIC (Gr. rcavvraubs, burning)

caustic alkalis, a behaviour which distinguishes it from the yellow sulphides of arsenic and tin. Cadmium is estimated quantitatively by See also:

CONVERSION (Lat. conversio, from convertere, to turn or ,change)

conversion into the oxide, being precipitated from boiling solutions by the addition of See also:

SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

sodium carbonate, the carbonate thus formed passing into the oxide on ignition. It can also be determined as sulphide, by precipitation with sulphuretted hydrogen, the precipitated sulphide being dried at too° C. and weighed. The atomic weight of cadmium was found by 0. W. See also:

Huntington (Berichte, 1882, 15, p. 8o), from an See also:

ANALYSIS (Gr. avci and Meta, to break up into parts)

analysis of the pure bromide, to be 111.9. H. N.

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