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.
It crystallizes in large monoclinic prisms which melt at 97.5° C., and distils between 302° and 304° C., practically without decomposition.
By evaporating in vacuo the solution obtained by dissolving iron in hydrochloric acid, there results bluish, monoclinic crystals of FeCl24H20, which deliquesce, turning greenish, on exposure to air, and effloresce in a desiccator.
Ferrous sulphate forms large green crystals belonging to the monoclinic system; rhombic crystals, isomorphous with zinc sulphate, are obtained by inoculating a solution with a crystal of zinc sulphate, and triclinic crystals of the formula FeSO 4.5H 2 O by inoculating with copper sulphate.
Ferric nitrate, Fe(NO3) 3, is obtained by dissolving iron in nitric acid (the cold dilute acid leads to the formation of ferrous and ammonium nitrates) and crystallizing, when cubes of Fe(NO3)3.6H20 or monoclinic crystals of Fe(N03)3.9H20 are obtained.
It forms crystals, apparently monoclinic, which melt at 22.5° to a clear, colourless, mobile liquid of boiling-point 173-i°.
It is a soft, flocculent powder, which on sublimation forms transparent, monoclinic crystals.
The sodium salt, Na 4 P 2 0 6.10H 2 O, forms monoclinic prisms and in solution is strongly alkaline; the acid salt, Na3HP206.9H20, forms monoclinic tablets.
This is illustrated by the hexagonal pyrargyrite 3Ag 2 S Sb 2 S 3, and proustite, 3Ag 2 S As2S3, and the monoclinic pyrostilpnite, isomeric with pyrargyrite, and xanthoconite, isomeric with proustite.
The crystals belong to the monoclinic system, and it is a curious fact that in habit and angles they closely resemble pyroxene (a silicate of calcium, magnesium and iron).
It crystallizes in the monoclinic system, and separates from its aqueous solution as Ba(Br03)2.H20.
It crystallizes in monoclinic prisms of composition Ba(C10 3) 2 H 2 O, and begins to decompose on being heated to 250° C. Barium iodate, Ba(103)2, is obtained by the action of excess of iodic acid on hot caustic baryta solution or by adding sodium iodate to barium chloride solution.