The focus of the present work is laid on clarifying the leaching mechanism and the influence of the precursor alloy on the catalyst`s properties with the aim of providing a basis for tayloring the properties of activated nickel catalysts for specific applications. A literature review about several aspects of Raney nickel is given. In this review it is shown that especially the leaching mechanism which is the basis of the catalyst`s development is not fully understood. Furthermore, a systematic study on the influence of precursor alloys produced by different methods is not reported. For the investigations different nickel-aluminium precursor alloys were used, particulary cast and milled nickel-aluminium alloys and atomized nickel-aluminium alloys. In addition to the binary alloys, chromium and iron were added partially as promotor elements to enhance the catalytic activity. The alloys were characterized using X-ray diffraction and quantitative image analysis. Nickel catalysts werde produced by leaching the alloys in alkali solution. Morphology and microstructure were characterized using SEM, TEM and XRD. The inner surface was measured in some samples by nitrogen adsorption. The concentration of the residual aluminium was determined by EDX. Catalytic activity was measured in the hydrogenation of nitrobenzene. Precursor alloys consist of small amounts of aluminium and the intermetallic phases NiAl3 and Ni2Al3. The leaching kinetics of these phases were shown to be different. Higher aluminium content leads to a faster reaction. The leaching mechanism consists of the selective dissolution of aluminium, accompanied by short order rearrangement of the remaining atoms. During leaching the NiAl3-Phase transforms directly to face centered cubic (fcc) nickel. In the case of the Ni2Al3-Phase, a metastable intermediate phase is forming. This intermediate phase has a composition of about Ni-30at% Al. The crystal structure is body centered cubic (bcc) with the nickel and aluminium atoms statistically distributed on the bcc lattice positions. The leaching mechanism is based on a correlation of the Ni2Al3-structure and the bcc-phase. Further leaching and consequently further dissolution of aluminium leads to the transformation of the bcc-phase into fcc-Nickel solid solution. After complete leaching, the nickel catalyst still contains a considerable amount (15 at.%) of residual aluminium. It is shown that the residual aluminium is distributed in the fcc-nickel solid solution and the bcc-phase.The precursor alloys contain different amounts of the phases NiAl3 and Ni2Al3. The Ni2Al3 fraction correlates with the amount of residual aluminium in the catalyst. The higher the Ni2Al3 fraction in the precursor alloy, the higher is the residual aluminium concentration after leaching. In this context, significant differences were found between the nickel catalysts from the atomized and the milled alloy powders. In case of the cast and milled precursor alloys, the activity of the nickel catalysts was found to increase temperature independently with increasing leaching time in the temperature range between 75 and 110°C. In case of the atomized alloys, the activity increases with increasing leaching time at 75°C, at 110°C the activity decreases with increasing leaching time. This drop of the activity at the higher temperature is attributed to a decrease of the inner surface due to sintering of the nanosized active catalyst units.