CHROMIUM

(Lat.), n. n. Krom(ch2rom)'ia-u3m(u4m). From xpiofj-a, color, from the variety of color exhibited by its compounds. Fr., chrome. Ger., Chrom. It., Sp., cromo. A metallic element discovered by Vauquelin in 1797. It is found in various minerals combined with lead or iron. It may be obtained either in the form of a light-green micro-crystalline powder, or as a hard solid fusible with difficulty. It is not readily oxidized, and is not attacked by nitric acid, but di olves in hydrochloric or hot sulphuric acid. Sp. gr., about 7. In compounds it acts as a dyad, forming chromous compounds; as a tetrad or pseudo-triad, forming chromic compounds; and occasionally as a hexad, as in chromic acid. There is also the hypothetical per chromic anhydride, CrOT, in which c. may be regarded as an octad. Symbol, Cr.; atomic weight, 52'4. [B, 3, 77 (a, 24).] C. acetate. Fr., acetate de chrome. Ger., Chroma cet at, e igsaures Chromoxydul. It., aceta to di cromo. Sp., aceta to de cromo. A compound of c. and acetic acid. Two c. acetates are known: 1. Chromous acetate, Cr^BsOn)-! + H2O, known as red c. acetate, forming prismatic crystals. 2. Chromic acetate, C2(CaHsO2)8 + 2H2O. [B, 2 (a, 24); B, 3.J See also C. basic acetate. C. alum. See C. and pota ium sulphate. C. and ammonium sulphate. Fr., sulfate de chrome et d'ammonia que. Ger., schwefelsaurer Chromoxydammoniak. Ammonia-chromic alum; a substance forming ruby-colored crystals, Cr2(SO4 )3.(NH4)2SO4 + 24H2O. [B, 3.] C. and pota ium sulphate. Fr., sulfate de chrome et de pota e. A compound of c. and pota ium with sulphuric acid; c. alum. Three c. and pota ium sulphates are known: 1. Pota io-chromous sulphate, Cr.SO4.K2SO4 + 6H2O, forming blue prismatic crystals. 2. Pota io-chromic sulphate (Ger., schwefelsaures Chromoxyd-Kali, Cra[SO4] s.K2SO4-i-24H2O), otherwise called chrome-alum. It forms dark-purple octahedral crystals, appearing red by transmitted light. It is used in dyeing and in tanning. 3. Another pota io-chromic sulphate exists under the form of minute green acicular crystals, Cr2(SO4)3.3K.jSO4, the common variety of chrome alum. [B, 3.] C. and sodium sulphate. Fr., sulfate de chrome et de soude. Ger., schwefelsaures Chromoxyd-Natron. A substance of the composition Cr2(SO4)3.3Na2SO4. [B, 3.] C. arsenate. Fr., arseniate de chrome. Ger., arsensaures Chromoxyd. It., arseniato di cromo. Sp., arseniato de cromo. A compound of c. and arsenic acid. Chromic arsenate is an apple-green substance precipitated from a solution of a chromic salt by the addition of pota ium arsenate. [B, 2.] C. basic acetate. Fr., acetate basique de chrome. Ger., basisch e igsaures Chromoxyd. It., aceta to basico di cromo. Sp., aceta to basico de cromo. A compound of c. oxide or c. hydroxide with acetic acid. Basic chromic acetate, Cr2(OH)2(C2H3O2)4, is known. A variety of derivatives of chromic acetate, in which, like this basic derivative, part of the acetic-acid radicle is replaced by other radicles, are also known. [B, 2.] C. basic sulphate. Fr., sulfate basique de chrome. Ger., basisch schwefelsaures Chromoxyd. It., solfato basico di cromo. Sp., sulfa to basico de cromo. A compound of c. oxide or c. hydroxide with sulphuric acid. Several basic chromic sulphates exist; one, forming an amorphous red ma , has the constitution Cr2O.(SO4)a; another, pale-green in color, has the formula 2Cr2SO4.(OH)4.Cr2(OH)9 + 5H2O. [B, 3.] C. bromide. Fr., bromure de chrome. A compound of c. and bromine. Two c. bromides are known: 1. Chromous bromide (Ger., Chrombromur), a white crystalline ma , CrBr2, turning green on exposure to the air from the formation of an oxy bromide of c. 2. Chromic bromide (Fr., bromure chromique; Ger., Chrombromid; It., bromuro cromico; Sp., bromuro cromico), CraBr,, forming dark-green translucent scales. [B, 3.] C. chloride. Fr., chlorure de chrome. A compound of c. and chlorine. Two c. chlorides are known: 1. Chromous chloride (Ger., Chromchlorur), CrCl2, forming silky-white acicular crystals, and by its affinity for oxygen acting as a strong reducing agent. 2. Chromic chloride (Fr., chlorure chromique; Ger., Chromchlorid; It., cloruro cromico; Sp., cloruro cromico), forming pinkish scales, CraCl6, or green acicular crystals, Cr2Cl6 + 12H2O; used as a coloring agent. [B, 3.] See also C. oxy chloride. C. chromate. Fr., chromate de chrome. Ger., chromsaures Chromoxyd. It., pero ido (o cromato) di cromo. Sp., cromato de cromo. A compound of c. sesquioxide with c. trioxide. The compound ordinarily so called is also denominated c. dioxide or peroxide, and has the composition CraO3.CrO3 = 3CrO2. It is a black or brownish powder. Another compound is known, having the formula Cr6O8 = 2CrO3 + CrO3, and forming violet-colored prismatic crystals. [B, 3.] C. cyanide. Fr., cyanure de chrome. A compound of c. and cyanogen. Two c. cyanides are known: 1. Chromous cyanide (Fr., cyanure chromeux; Ger., Chromcyaniir), a white substance,.Cr(CN)2, changing to green on exposure to the air. 2. Chromic cyanide (Fr., cyanure chromique; Ger., Chromcyanid; It., cianuro cromico; Sp., cianuro cromico), a pale-green substance, Cr2(CN), forming, by combination with other metals, the chromicyanides. C. dioxide. Fr., bioxyde (ou dioxyde) de chrome. See C. chromate. C. dioxydichloride. See CHROMYL chloride. C. ferricyanide. Fr.. ferricyanure de chrome. Ger., Ferridcyanchrom. A compound, Cr2Fe2(C3N3 >4, formed by the action of c. trichloride on pota ium ferricyanide. It is soluble in water. [B, 4 (a, 24).] -C. fluoride. Fr.,fluorure de chrome. Ger., Chromfluorid. 1t.,fluoruroclicri>mo. Sp., fluoruro de cromo. A compound of c. and fluorine. Chromic fluoride, Cr2F6, a greenish crystalline ma , is known. [B, 3.J See also C. hex fluoride.C. hex fluoride. A substance, CrF6, forming a scarlet fuming liquid which is readily converted into a reddish gas of strongly irritant properties. [B, 3, 158 (a, 24).] C. hydrate. See C. hydroxide. C. hydro chlorate. A compound of the composition CrO2 5 -j C. hydroxide. Fr., hydrate de chrome. Ger., Chromhydrat. It., idrato di cromo. Sp., hidrato de cromo. Syn.: c. hydrate. A compound of c. and hydroxyl. Several hydroxides of c. exist: 1. Chromous hydroxide (Ger., Chromoxydulhydrat), Cr(OH)2, a brownish-yellow precipitate prepared by precipitating chromous chloride with caustic potash. It readily oxidizes on exposure to the air, and is converted into c. sesquioxide. 2. Chromic hydroxide, chromic O, no; O*, not; O, whole.; Th, thin; Th, the; U, like oo in too; [s. 265]