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KNO2

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Originally appearing in Volume V06, Page 605 of the 1911 Encyclopedia Britannica.

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KNO2 .3H20, is best known. It may be prepared by the addition of See also:

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

potassium nitrite to an acetic See also:

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

acid See also:

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

solution of See also:

COBALT (symbol Co, atomic weight 59)

cobalt chloride. The yellow precipitate obtained is washed with a solution of potassium acetate and finally with dilute See also:

ALCOHOL

alcohol. The reaction proceeds according to the following See also:

EQUATION (from Lat. aequatio, aequare, to equalize)

equation: 2CoC12+10KNO2+ 4HNO2=See also:

Co2(NO2)6•6KNO2+4KC1+2N0+2H20 (A. Stromeyer, Annalen, 1855, 96, p. 220). This See also:

salt may be used for the separation of cobalt and See also:

nickel, since the latter See also:

metal does not See also:

FORM (Lat. forma)

form a similar See also:

double nitrite, but it is necessary that the alkaline See also:

earth metals should be absent, for in their presence nickel forms complex nitrites containing the alkaline earth metal and the See also:

ALKALI

alkali metal. A See also:

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

sodium cobaltinitrite is also known. Cobalt nitrate, Co(NO3)2.6H2O, is obtained in dark-red mono-clinic tables by the slow evaporation of a solution of the metal, its hydroxide or carbonate, in nitric acid. It deliquesces in the See also:

air and melts readily on See also:

HEATING

heating. By the addition of excess of See also:

AMMONIA (NH3)

ammonia to its aqueous solution, in the See also:

COMPLETE

complete See also:

ABSENCE (Lat. absentia)

absence of air, a See also:

BLUE (common in different forms to most European languages)

blue precipitate of a basic nitrate of the See also:

composition 6CoO•N203.5H2O is obtained. By boiling a solution of cobalt carbonate in phosphoric acid, the acid phosphate CoHPO4.3H2O is obtained, which when heated with See also:

WATER

water to 250° C. is converted into the neutral phosphate See also:

Cos(PO4)2.2H20 (H.

Debray, See also:

Ann. de chimie, 1861, [3] 61, p. 438). Cobalt ammonium phosphate, CoNH4PO4.12H2O, is formed when a soluble cobalt salt is digested for some See also:

time with excess of a warm solution of ammonium phosphate. It separates in the form of small See also:

rose-red crystals, which decompose on boiling with water. Cobaltous See also:

CYANIDE

cyanide, Co(CN)2.3H20, is obtained when the carbonate is dissolved in hydrocyanic acid or when the acetate is precipitated by potassium cyanide. It is insoluble in dilute acids, but is readily soluble in excess of potassium cyanide. The double cyanides of cobalt are analogous to those of See also:

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

iron. Hydrocobaltocyanic acid is not known, but its potassium salt, K4Co(CN)3, is formed when freshly precipitated cobalt cyanide is dissolved in an See also:

ICE (a word common to Teutonic languages; cf. Ger. Eis)

ice-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 solution of potassium cyanide. The liquid is precipitated by alcohol, and the washed and dried precipitate is then dissolved in water and allowed to stand, when the salt separates in dark-coloured crystals. In alkaline solution it readily takes up See also:

OXYGEN (symbol 0, atomic weight 16)

oxygen and is converted into potassium cobalticyanide, K3Co(CN)s, which may also be obtained by evaporating a solution of cobalt cyanide, in excess of potassium cyanide, in the presence of air, 8KCN+2Co(CN)2+See also:

H2O (combined)

H2O+O= 2K3Co(CN)4+2KHO. It forms See also:

MONOCLINIC

monoclinic crystals which are very soluble in water. From its aqueous solution, concentrated hydrochloric acid precipitates hydrocobalticyanic acid, H3Co(CN)6, as a colourless solid which is very deliquescent, and is not attacked by concentrated hydrochloric and nitric acids.

For a description of the various•salts of this acid, see P. Wesselsky, Berichte, 1869, 2, p. 588. Cobaltammines. A large number of cobalt compounds are known, of which the empirical composition represents them as salts of cobalt to which one or more molecules of ammonia have been added. These salts have been divided into the following See also:

SERIES (a Latin word from serere, to join)

series : Diammine Series, [Co(NH3)2]X4M. In these salts X=NO2 and M =one atomic proportion of a monovalent metal, or the See also:

EQUIVALENT

equivalent quantity of a divalent metal. Triammine Series, [Co(NH3)s]X2. Here X = Cl, NO3, NO2, 4SO4, &c. Tetrammine Series. This See also:

GROUP

group may be divided into the •Praseo-salts [R2Co(NH3)4]X, where X=C1. Croceo-salts [(NO2)2Co(NH3)4]X, which may be considered as a subdivision of the praseo-salts.

Tetrammine purpureo-salts [RCo(NH3)4•H2O]X2. Tetrammine roseo-salts [Co(NH3)4•(H2O)2]X3. Fuseo-salts [Co(NH3)4]OH•X2. Pentammine Series. Pentammine purpureo-salts [R•Co(NH3)s]X2 where X = Cl, Br, NO3, NO2, SO4, &c. Pentarntnine roseo-salts [Co(NH3)s•H2O]X2. Hexammine or Luteo Series [Co(NH3)6]X3. The hexammine salts are formed by the oxidizing See also:

ACTION

action of air on dilute ammoniacal solutions of cobaltous salts, especially in presence of a large excess of ammonium chloride. They form yellow or See also:

BRONZE

bronze-coloured crystals, which decompose on boiling their aqueous solution. On boiling their solution in See also:

CAUSTIC (Gr. rcavvraubs, burning)

caustic alkalis, ammonia is liberated. The pentammine purpureo-salts are formed from the luteo-salts by loss of ammonia, or from an air slowly oxidized ammoniacal cobalt salt solution, the precipitated luteosalt being filtered off and the filtrate boiled with concentrated acids. They are See also:

VIOLET

violet-red in See also:

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

colour, and on boiling or See also:

long See also:

STANDING

standing with dilute acids they pass into the corresponding roseo-salts.

The pentammine nitrito salts are known as the xanthocobalt salts and have the See also:

general See also:

formula [NO2•Co•(NH3)s]X2. They are formed by the action of nitrous fumes on ammoniacal solutions of cobaltous salts, or purpureo-salts, or by the mutual reaction of chlorpurpureosalts and alkaline nitrites. They are soluble in water and give characteristic precipitates with platinic and auric chlorides, and with potassium ferrocyanide. The pentammine roseo-salts can be obtained from the action of concentrated acids, in the cold, on air-oxidized solutions of cobaltous salts. They are of a reddish colour and usually crystallize well ; on heating with concentrated acids are usually transformed into the purpureo-salts. Their alkaline solutions liberate ammonia on boiling. They give a characteristic 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 red precipitate with sodium pyrophosphate, soluble in an excess of the precipitant; they also form arecipitates on the addition ofplatinic chloride and potassium ferrocyanide. For methods of preparation of the tetrammine and triammine salts, see O. Dammer's Handbuch der anorganischen Chemie, vol. 3 (containing a complete See also:

account of the preparation of the cobaltammine salts). The diammine salts are prepared by the action of alkaline nitrites on cobaltous salts in the presence of much ammonium chloride or nitrate; they are yellow or See also:

brown crystalline solids, not very soluble in cold water. The above series of salts show striking See also:

DIFFERENCES, CALCULUS OF (Theory of Finite Differences)

differences in their behaviour towards reagents; thus, aqueous solutions of the luteo chlorides are strongly ionized, as is shown py their high electric conductivity; and all their See also:

CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine is precipitated on the addition of See also:

SILVER

silver nitrate solution.

The aqueous solution, however, does not show the See also:

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary reactions of cobalt or of ammop)a, and so it is to be presumed that the salt ionizes into [Co(NH3)s] and 3C1'. The purpureo chloride has only two-thirds of its chlorine precipitated on the addition of silver nitrate, and the electric conductivity is much less than that of the luteo chloride; again in the praseosalts only one-third of the chlorine is precipitated by silver nitrate, the conductivity again falling; while in the triammine salts all ionization has disappeared. For the constitution of these salts and of the " metal ammonia " compounds generally, see A. See also:

Werner, Zeit. See also:

FUR (connected with O. Fr. forre, a sheath or case; so " an outer covering ")

fur anorg. Chemie, 1893 et seq., and Berichte, 1895, et seq. ; and S. Jorgensen, Zeit. fur anorg. Chemie, 1892 et seq. The oxycobaltammines are a series of compounds of the general type [Co203•H2(NH3)10]Xs first observed by L. See also:

GMELIN

Gmelin, and subsequently examined by E. See also:

FREMY, EDMOND (1814–1894)

Fremy, W. See also:

Gibbs and G.

Vortmann (Monatshefte fur Chemie, 1885, 6, p. 404). They result from the cobaltammines by the See also:

DIRECT

direct taking up of oxygen and water. On heating, they decompose, forming basic tetrammine salts. The atomic See also:

WEIGHT

weight of cobalt has been frequently determined, the earlier results not being very concordant (see R. See also:

Schneider, Pog. Ann., 1857, 101, p. 387; C. See also:

MARIGNAC, JEAN CHARLES GALISSARD DE (1817-1894)

Marignac, See also:

Arch. Phys. Nat. [2], I, p.

373; W. Gibbs, Amer. Jour. Sci. [2], 25, p. 483; J. B. See also:

Dumas, Ann. Chim. Phys., 1859 [3], 55, p. 129; W. J.

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