Abstract: The invention relates to a lubricant of lubricating oil basis for lubricating rotating and/or sliding surfaces. Furthermore, the invention relates to a process for preparing this lubricant.The lubricant according to the invention comprises, beside the usual additives, 0.01 to 0.3 g/l of aluminium oxide power consisting of particles of 0.1 to 4 .mu.m in size.

Abstract: An apparatus for separating a slurry into phases containing larger and smaller grains has an upright tank in which a plurality of downwardly extending inlet pipes open at their lower ends between outlets for the coarse and fine phases located at the bottom and top of the tank, respectively. At the lower end of each inlet pipe, an upwardly widening frustoconical cup is provided with a bottom confronting the open end of the inlet pipe to deflect the slurry upwardly and outwardly. Within the cup swirl vanes impart a swirl to the slurry.

Abstract: A method of and apparatus for the mixing of a slurry in a tank having a conical bottom along the axis of the tank, and air-lift pipe is provided which is supplied at its lower end with compressed air to induce an upward flow of the slurry and air mixture through the pipe during start up of a mixing operation. Thus an injection is cut off when steady state is reached and air is injected at an upper level in the pipe located in the upper third of the length thereof but below the upper eighth for continuing mixing operation.

Abstract: Crushing equipment with air-jet, in particular for the comminution of crystalline materials, comprising a cylindrical grinding chamber, nozzles and a nozzle carrying crown. The nozzle carrying crown is assembled of two releasably interconnected crown-halves and an exchangeable wearing ring protecting the outlet opening of the nozzle, and the two crown-halves form the seat of the wearing ring. Useful life of the nozzles of the equipment is practically unrestricted. The nozzles are fit, without a thread, either into one of the crown-halves or between them.