Abstract: A method of isomerizing propargyl alcohol to acrolein, wherein propargyl alcohol is rearranged in the gas phase at a temperature of from 300.degree. to 550.degree. C. and a pressure of from 0.01 to 50 bar and in contact with a heterogeneous catalyst containing alkaline-reacting metal ions, and the use of propargyl alcohol as a depot substance for the liberation of acrolein.

Abstract: Isometric cobalt- and titanium-containing magnetic iron oxides are prepared by reacting acicular iron(III) oxide hydroxides with compounds of divalent cobalt and iron and compounds of tetravalent titanium in aqueous alkaline suspension at elevated temperature.

Abstract: A process for the preparation of mixtures of isomeric cresols with a molar ratio of para- to meta-cresol of from 0.6:1 to 10:1 by isomerization of cresol mixtures or ortho- and/or metal-cresol on zeolite catalysts of the pentasil type in the gas phase at from 300.degree. to 600.degree. C. under from 0.01 to 50 bar entails the mean particle size of the zeolite catalyst being at leat 3 .mu.m, and the selectivity in the established test for the disproportionation of ethylbenzene to diethylbenzene isomers being at least 60% for para-diethylbenzene.

Abstract: Acicular ferromagnetic chromium dioxide is stabilized by treatment with an alkali metal hydroxide in an aqueous alkaline suspension at elevated temperatures.

Abstract: A process for the separation of ortho-, meta- and para-tolunitrile from ternary mixtures of isomers entails removing ortho-tolunitrile from these mixtures by distillation under pressures of from 10.sup.2 and 10.sup.5 Pa and with a reflux ratio of from 1:1 to 200:1, and distilling the remaining binary mixture of meta- and para-tolunitrile to concentrate to more than 75 mol-% para-tolunitrile, and freezing out the paratolunitrile at below 26.degree. C., and a process for the preparation of suitable ternary mixtures of isomers entails isomerization of pure ortho-, meta- or para-tolunitrile or mixtures thereof at from 380.degree. to 580.degree. C. on zeolite catalysts.

Abstract: Hydroxybenzaldehydes of the formula (I) are prepared from a benzaldehyde of the formula (II) or its acetal, in which R.sup.1 in the R.sup.1 O-phenyl ether group is an alkyl, cycloalkyl, alkylcycloalkyl or alkylaryl radical, R.sup.2 is H or OH or is identical to R.sup.1 and one or more R.sup.1 O-phenyl ether groups are ortho, meta or para to the aldehyde function, by a process in which a benzaldehyde of the formula (II) or its acetal, in which R.sup.1 and R.sup.2 have the abovementioned meanings and one or more R.sup.1 O-phenyl ether groups occupy the abovementioned position with respect to the aldehyde function, is converted into a hydroxybenzaldehyde of the formula (I) in the presence of water over a zeolite as a heterogeneous catalyst. ##STR1## The catalysts used are, in particular, zeolites of the pentasil type.

Abstract: Acicular, ferromagnetic metal particles which essentially consist of iron and have a nickel content of not more than 0.4% by weight and high values for coercive force and magnetization, and a process for the preparation of these particles. The particles further include zinc, phosphorus in the form of phosphate ions, and silicon in the form of SiO.sub.2.

Abstract: Ferromagnetic metal particles of substantially iron are prepared by starting from an acicular .alpha.-FeOOH, applying a shape-stabilizing finish to the particle surface, heating at 500.degree.-850.degree. C. and subsequently reducing with gaseous reducing agents at 200.degree.-500.degree. C. to the metal, and starting .alpha.-FeOOH being prepared in the presence of zinc and phosphate ions.

Abstract: Finely divided, acicular and pore-free .alpha.-Fe.sub.2 O.sub.3 is prepared from iron(III) salts in the presence of one or more organic substances which form complexes with iron(III) ions, in alkaline suspension, at from 80.degree. to 250.degree. C.

Abstract: Superparamagnetic solid particles of the general formula IM.sub.v Mn.sub.w Zn.sub.x Fe.sub.y O.sub.z (I)where M is Co and/or Ni, v and w are each from 0 to 0.998, x is from 0.001 to 0.998, y is from 2.001 to 2.998, z is from 3.001 to 4, v+w+x is from 0.002 to 0.999, v+w+x+y is 3, v.noteq.0 if w=0 and w.noteq.0 or v=0, polar and nonpolar superparamagnetic liquids which contain the surfactant-coated superparamagnetic solid particles I in the form of a colloidal dispersion in polar or nonpolar liquid media, and processes for the preparation of polar and nonpolar superparamagnetic liquids.

Abstract: Ferromagnetic chromium dioxide is improved by subjecting chromium dioxide materials prepared by a known method to an additional heat treatment.

Abstract: Acicular .alpha.-Fe.sub.2 O.sub.3 is prepared from iron(III) salts by heating an alkaline aqueous suspension of iron(III) hydroxide in the presence of one or more organic substances which form complexes with iron(III) ions to a temperature of 100.degree. C. or less.

Abstract: Acicular, magnetic iron oxide consisting of a core of gamma-iron(III) oxide and a ferrite shell containing a total of from 0.4 to 12% by weight of cobalt(II) ions and from 0.1 to 15% by weight of iron(II) ions, the percentages being based on the total amount of magnetic material, is prepared by a process in which an iron(II) hydroxide precipitate is applied to the gamma-iron(III) oxide core in a first stage and an iron-(II)/cobalt hydroxide precipitate is applied to the said core in a second stage, and the core is then converted to the ferrite shell by oxidation.

Abstract: A process for the preparation of cobalt-containing isotropic magnetic iron oxides which are based on gamma-iron(III) oxide, contain from 2 to 7% by weight of cobalt(II) ions and less than 2% by weight of Fe(II) ions, the percentages in each case being based on the iron oxide, and have a particle length of from 0.08 to 0.30 .mu.m, a length/width ratio of from 1.5 to 3.5:1 and a specific remanent magnetization after saturation of not less than 60 nTm.sup.3 /g.

Abstract: The preparation of acicular ferrimagnetic iron oxides which contain cobalt and phosphate ions and, if desired, further additives, and their use for manufacturing magnetic recording media.

Abstract: Acicular metal particles consisting essentially of iron are prepared by reducing .alpha.-iron(III) oxide obtained--by dehydration--from acicular iron(III) oxide hydroxide prepared in the presence of phosphate ions and having a shape-stabilizing surface coating.

Abstract: Ferrimagnetic particles which are useful as magnetic material for magnetic recording media and consist of a core of a magnetic material exhibiting multiaxial anisotropy and a coating which surrounds the core and is composed of a magnetic material possessing uniaxial anisotropy, and a process for their preparation.

Abstract: Acicular ferromagnetic chromium dioxide particles having a pH greater than 4 and a process for their preparation.

Abstract: A process for the manufacture of acicular ferrimagnetic iron oxide by converting acicular iron(III) oxide hydroxide at from 300.degree. to 650.degree. C., by treatment with an organic compound which decomposes in this temperature range in the presence of iron oxide, the iron(III) oxide hydroxide used for the reaction being a lepidocrocite which has been heat-treated at from 300.degree. to 700.degree. C.

Abstract: Acicular ferromagnetic metal particles consisting essentially of iron are prepared by a process wherein acicular iron(III) oxide hydroxide provided with a shape-stabilizing surface coating, or iron(III) oxide obtained therefrom by dehydration, is reduced by means of a decomposable organic compound and hydrogen.