Abstract: A method for producing sulfur plates comprises producing an aqueous mixture by mixing and agitating sulfur powder, inorganic powder, fibers and water, filtering the aqueous mixture to form plates, molding the plates while dewatering, curing and drying the plates, and heating the plates at a temperature higher than the melting point of the sulfur. The sulfur plates attain a desired strength in a short time and are free from any cracks and have an excellent acid resistance.

Abstract: A workpiece which may be made of a highly electrically insulating material is held in a spaced opposing relationship with respect to a silent discharge plate electrode to which an a.c. voltage is applied. A d.c. voltage is applied across the workpiece and the silent discharge plate electrode to form a driving electric field therebetween. Powder particles suspended in air are charged in the same polarity as that of the silent discharge plate electrode and then injected into the region between the silent discharge plate electrode and the workpiece where the electric field drives the charged particles toward the workpiece to coat it. The a.c. voltage is sufficient to repel the electrode surface confronting the workpiece and to maintain the silent discharge at a reduced level and effectively precluding deposit of powder particles on the mentioned surface. An apparatus for the electrostatic coating is also disclosed.

Abstract: This invention relates to a process for treating a sludge or a drainage containing chromium (VI) compounds with a calcium haloaluminate bearing rapid hardening cement in a short period of time. The solidified material developes high strength and has shown a extremely Cr.sup.6+ fixation.

Abstract: Apparatus for calcining wet powdery gypsum which comprises:(A) a furnace which generates a hot gas having a temperature higher than 900.degree.

Abstract: This invention relates to a super rapid hardening mixture comprisingA. a super rapid hardening cement in which 11CaO.7Al.sub.2 O.sub.3. CaZ (X is a halogen atom), 3CaO.SiO.sub.2 and CaSO.sub.4 are present as indespensable components;B. at least one short range strength accelerator selected from the group consisting of a calcium aluminate material, a lime material, an amine and an ethylene glycol material and calcium sulfate hemihydrate;C. at least one emulsion selected from the group consisting of a bituminous emulsion, a rubber latex and a resin emulsion;D. from 12 to 50 weight percent of water in the total mixture.

Abstract: A sludge having a water/solid high ratio and containing a substance having a harmful influence upon the setting of portland cement is solidified by mixing the sludge with rapid hardening cement containing calcium haloaluminate.

Abstract: A sludge having a water/solid high ratio and containing a substance having a harmful influence upon the setting of portland cement is solidified by mixing the sludge with hydraulic portland cement and at least one substance selected from the group consisting of alkali sulphate, gypsum dihydrate and insoluble gypsum anhydride.