It forms monoclinic crystals which are very soluble in water.
VIVIANITE, a mineral consisting of hydrated iron phosphate Fe 3 (PO 4) 2 +8H 2 0, crystallizing in the monoclinic system.
O COC 6 H 5, prepared from phenol and benzoyl chloride, crystallizes in monoclinic prisms, which melt at 68-69° C. and boil at 314° C.
It seems rather doubtful whether the unstable monoclinic modification of sulphur (0 - sulphur) is ever found in a native state.
Allotropic Modifications.-Sulphur assumes crystalline, amorphous and (possibly) colloidal forms. Historically the most important are the rhombic (Sa) and monoclinic (So) forms, discussed by E.
The common monoclinic variety is obtained by allowing a crust to form over molten sulphur by partially cooling it, and then breaking the crust and pouring off the still liquid portion, whereupon the interior of the vessel will be found coated with long needles of this variety.
Three other monoclinic forms have been described.
Engel's monoclinic form (Compt.
Crystals of azurite belong to the monoclinic system; they have a vitreous lustre and are translucent.
It crystallizes in monoclinic tables which melt at 148-149° C. Chromic acid oxidizes it to pyrene quinone, C16H802, and pyrenic acid, C15H1806.
Wallach, Ann., 1878, 193, p. 25) It crystallizes in monoclinic tables, and is readily soluble in water, alcohol and ether.
Again, the pyroxenes, RS103 (R=Fe, Mg, Mn, &c.), assume the forms (I) monoclinic, sometimes twinned so as to become pseudo-rhombic; (2) rhombic, resulting from the pseudo-rhombic structure of (I) becoming ultramicroscopic; and (3) triclinic, distinctly different from (I) and (2); (I) and (2) are polysymmetric modifications, while (3) and the pair (I) and (2) are polymorphs.
The above may be illustrated by considering the equilibrium between rhombic and monoclinic sulphur.
The former, which is deposited from solutions, is transformed into monoclinic sulphur at about 96°, but with great care it is possible to overheat it and even to fuse it (at 113.5°) without effecting the transformation.
Monoclinic sulphur, obtained by crystallizing fused sulphur, melts at I 19.5°, and admits of undercooling even to ordinary temperatures, but contact with a fragment of the rhombic modification spontaneously brings about the transformation.
From Reicher's determinations, the exact transition point is 95.6°; it rises with increasing pressure about 0.05° for one atmosphere; the density of the rhombic form is greater than that of the monoclinic. The equilibria of these modifications may be readily represented on a pressure-temperature diagram.
The line BC, representing the equilibrium between monoclinic and liquid sulphur, is thermodynamically calculable; the point B is found to correspond to 131° and 400 atmospheres.
Of especial interest is the 0 curve BD; along this line liquid and rhombic sulphur are in equilibrium, which means that at above 131° and 400 atmospheres the rhombic (and not the monoclinic) variety would separate from liquid sulphur.
Telluric acid forms cubic and monoclinic crystals from a hot nitric acid solution, and ammonium fluosilicate gives cubic and hexagonal forms from aqueous solutions between 6° and 13°.
Magnesium sulphate (orthorhombic) takes up ferrous sulphate (monoclinic) to the extent of 19%, forming isomorphous orthorhombic crystals; ferrous sulphate, on the other hand, takes up magnesium sulphate to the extent of 54% to form monoclinic crystals.
By plotting the specific volumes of these mixed crystals as ordinates, it is found that they fall on two lines, the upper corresponding to the orthorhombic crystals, the lower to the monoclinic. From this we may conclude that these salts are isodimorphous: the upper line represents isomorphous crystals of stable orthorhombic magnesium sulphate and unstable orthorhombic ferrous sulphate, the lower line isomor phous crystals of stable monoclinic ferrous sulphate and unstable monoclinic magnesium sulphate.
They all crystallize in the monoclinic system, often, however, in forms closely resembling those of the rhombohedral or orthorhombic systems. Crystals have usually the form of hexagonal or rhomb-shaped scales, plates or prisms, with plane FIG.
Dark coloured micas are strongly pleochroic. Accurate determinations of the optical orientation, as well as the symmetry of the etching figures on the cleavage planes, seem to suggest that the micas, except muscovite, may be anorthic rather than monoclinic in crystallization.
By dissolving red lead, Pb304, in glacial acetic acid and crystallizing the filtrate, colourless monoclinic prisms of lead tetracetate, Pb(C2H302)4, are obtained.
Stannous Fluoride, SnF 2, is obtained as small, white monoclinic tables by evaporating a solution of stannous oxide in hydrofluoric acid in a vacuum.
When slowly crystallized it forms large monoclinic prisms which are readily soluble in water but difficultly soluble in alcohol.
COC 6 H 6 CH Anthracene crystallizes in colourless monoclinic tables which show a fine blue fluorescence.
H 2 O, forms white, shining, monoclinic scales.
It crystallizes from water (in which it is very soluble) in monoclinic prisms which approximate in composition to Sr(N03)2.4H20 or Sr(N03)2.5H20.
Light-yellow monoclinic needles of 2KAuC1 4 H 2 O are deposited from warm, strongly acid solutions, and transparent rhombic tables of KAuCl 4.2H 2 O from neutral solutions.
It forms colourless, monoclinic prisms, which turn brown on exposure to air.
Zirconium fluoride, ZrF4, is obtained as glittering monoclinic tables (with 3H 2 0) by heating zirconia with acid ammonium fluoride.
It forms monoclinic prisms (with IoH 2 O) which are permanent in air.
In combination with calcium sulphate, it constitutes the mineral glauberite or brongniartite, Na2S04 CaS041 which assumes forms belonging to the monoclinic system and occurs in Spain and Austria.
At ordinary temperatures it crystallizes from aqueous solutions in large colourless monoclinic prisms, which effloresce in dry air, and at 35° C. melt in their water of crystallization.
Calcium nitrate, Ca(N0,)2.4H20, is a highly deliquescent salt, crystallizing in monoclinic prisms, and occurring in various natural waters, as an efflorescence in limestone caverns, and in the neighbourhood of decaying nitrogenous organic matter.
The mineral brushite, CaHPO 4.2H 2 0, which is isomorphous with the acid arsenate pharmacolite, CaHAs04.2H20, is an acid phosphate, and assumes monoclinic forms. The normal salt may be obtained artificially, as a white gelatinous precipitate which shrinks greatly on drying, by mixing solutions of sodium hydrogen phosphate, ammonia, and calcium chloride.
Calcium metasilicate, CaSiO 3, occurs in nature as monoclinic crystals known as tabular spar or wollastonite; it may be prepared artificially from solutions of calcium chloride and sodium silicate.
Several hydrates are known: 2NaOH 7H 2 O is obtained as large monoclinic crystals by' cooling a solution of specific gravity 1.365 to -8'; Pickering (Journ.
The bromide and iodide crystallize from hot solutions in anhydrous cubes; from solutions at ordinary temperatures in monoclinic prisms with 2H 2 O; and at low temperatures with 5H 2 O.
It crystallizes in dark red monoclinic prisms which are readily soluble in water.
Occasionally monoclinic crystals are obtained by crystallizing from a strong solution.
Aluminium sulphate crystallizes as Al 2 (SO 4) 3.181120 in tablets belonging to the monoclinic system.
It is a colourless solid, which melts at 80° C., and boils at 218° C. It crystallizes in the monoclinic system; it is to be noted that aand 0-naphthol assume almost identical forms, so that these three compounds have been called isomorphous.
It forms resplendent monoclinic prisms, soluble in water.
Fluoranthene crystallizes in large slender needles or monoclinic tables, melting at 109-110° C. and boiling at 250-251° C. (60 mm.).
Evaporation of a solution at ordinary temperatures gives colourless monoclinic prisms of Th(SO 4) 2.9H 2 O, which is isomorphous with uranium sulphate, U(S04)2.9H20.
It loses four molecules of water of crystallization when heated to 100° C. and becomes anhydrous at about 300° C. The hexahydrate is dimorphous, a tetragonal form being obtained by crystallization of a solution of the heptahydrate between 20° and 30° C., and a monoclinic form between 50° and 70° C. Nickel sulphate combines with many metallic sulphates to form double salts, and also forms addition compounds with ammonia aniline and hydroxylamine.
The salt forms large monoclinic prisms; molecules containing 25 and 21 H 2 O separate from solutions crystallized at higher temperatures.
It crystallizes in the monoclinic system, and separates from its aqueous solution as Ba(Br03)2.H20.