Abstract: The stabilization of selected photochromic compounds, selected from certain fulgides and fulgimides, is made possible by associating with such compounds a clay mineral having an expanding crystal lattice, which can stabilize a selected photochromic compound in a higher-energy colored form. The stabilized photochromic compound may be one included in a coating composition, such as a paper coating composition, or may constitute or be incorporated in a filler for a papermaking furnish or for a plastics material. The stabilizer serves to maintain the photochromic compound in its higher-energy colored state or one of its higher-energy colored states, thereby tending to prevent deterioration of color as the photochromic compound converts to an uncolored or weakly colored lower-energy state.

Abstract: Raw bentonite is beneficiated by treating a substantially iron oxide-free bentonite, as an aqueous suspension, with an alkali at a temperature of at least 60.degree. C.; washing the alkali treated bentonite at least once with water; and then subjecting a suspension of the alkali-treated and washed bentonite to shearing, attrition and impact forces in a homogenizer of the type wherein the suspension is forced in the form of a film through a thin, hard-surfaced gap under a pressure of at least 1.7 MPa, and at high velocity. The suspension of bentonite thus obtained can then be dried to a product which has a good white color and is more resistent to bacteriological growth.

Abstract: A tube pressure filter is provided with a filter element comprising a filter cloth sleeve which is tailored from a woven material so that the warp and/or weft filaments extend helically around the inner tubular body on which the filter element is supported whereby the filter cloth sleeve can be stretched transversely of the length thereof.

Abstract: In order to make talc more readily dispersible in an aqueous medium, it is contacted, in a finely divided form, with an aqueous solution of an alkali metal hydroxide or ammonium hydroxide, it is then washed with clean water, whereafter it is thermally dried to remove at least a substantial proportion of the water associated therewith. The talc thus treated can be suspended in water containing a dispersing agent.

Abstract: A tube pressure filter including an inner compartment having an inlet which comprises a substantially annular aperture extending around the lower end of the inner tubular body and debouching into the inner compartment. The substantially annular aperture is constructed and disposed so that, in use, feed material debouching therefrom has an upward component of velocity and is in communication with an ante-chamber into which a mixture to be pressure filtered can be introduced under pressure through a feed conduit, the feed conduit containing or co-operating with a non-return valve so as to prevent the flow back along the feed conduit of feed material to be pressure filtered which is under high pressure.

Abstract: In the method described fluid containing magnetizable particles is introduced into a separating chamber containing a fluid-permeable mass of magnetizable material and held therein for a finite length of time. During this time the magnetizable material is moved into a magnetic field where the fluid is drained from the magnetizable material leaving magnetizable particles entrained in this material. This draining may be achieved either by providing relative movement between the separating chamber and the magnetizable material or by discharging the fluid from the separating chamber. The magnetic separator described comprises a chain of separating chambers, and associated masses of magnetizable material, which are moved continuously through a separating zone in which a magnetic field is established by a magnet. In this zone each mass of magnetizable material is drained and, outside this zone, the magnetizable particles entrained in the magnetizable material are removed by flushing.

Abstract: A method of comminuting a solid material comprising calcium carbonate to obtain a product containing at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter is disclosed. The method comprises forming an aqueous suspension of the solid material which has a solids content of up to 50% by weight and contains a dispersing agent, comminuting the solid material in the suspension by agitating the suspension in admixture with a particulate grinding medium, separating from the suspension thereby obtained an aqueous suspension containing comminuted solid material, classifying the latter suspension to obtain an aqueous suspension of a fine product which contains at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter, flocculating the fine product by means of an electrolyte having a multivalent cation, and dewatering the aqueous suspension containing the comminuted and flocculated fine product.

Abstract: A stable, pumpable suspension of a calcium carbonate mineral is prepared by a method which includes the step of removing abrasive particles from a deflocculated, concentrated aqueous suspension of the calcium carbonate mineral by centrifuging the suspension at a solids content of at least 65% by weight under conditions such that the quantity of particles in said suspension having an equivalent spherical diameter larger than 10 .mu.m is reduced.

Abstract: A membrane pressure filter comprises a pressure chamber divided into non-intercommunicating first and second compartments by a substantially upright impermeable elastic membrane, said first compartment containing a filtering surface, and said impermeable elastic membrane either being constructed in a manner such that or co-operating with means such that, in use, when the material in said first compartment has a specific gravity which is greater than the specific gravity of the material in said second compartment, said membrane is constrained to adopt a shape such that the surface of the membrane opposite the filtering surface is substantially parallel to the filtering surface.

Abstract: A paper coating composition which comprises a dispersion of a pigment in an aqueous medium containing an adhesive, the pigment comprising a natural chalk whiting formed from the remains of coccoliths which has been processed so as to contain at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter, not more than 5% by weight of particles larger than 10 microns equivalent spherical diameter and not more than 0.5% by weight of particles larger than 53 microns.

Abstract: A magnetic separator, for separating magnetizable particles from a fluid, consists of a separating chamber filled with a paramagnetic packing material, and a magnet for establishing a magnetic field within the packing material. The packing material is pervious to the fluid. A process for separating magnetizable particles from a fluid consists in applying a magnetic field to the packing material while passing the fluid therethrough, so as to attract the magnetizable particles in the fluid to collecting sites within the packing material.

Abstract: In a method of dewatering by pressure filtration an aqueous suspension of a clay containing a small proportion of particles having an equivalent spherical diameter smaller than 1 micron, the improvement which comprises treating the aqueous suspension of the clay, prior to dewatering by pressure filtration at a pressure in excess of 150 pounds per square inch, with a water-soluble polyelectrolyte flocculant having a high density of positive charges.

Abstract: A magnetic field is established in a predetermined zone. A quantity of fluid, from which native magnetizable particles are to be separated, is passed through the predetermined zone; and, at the same time, a magnetizable material is passed through the predetermined zone in the same direction as the fluid, so that native magnetizable particles are attracted to the magnetizable material.

Abstract: Apparatus and method for magnetic separation. A magnetic field is established in a first zone by a magnet. Fluid containing magnetizable particles is passed through a separating chamber disposed in the first zone. The separating chamber comprises a rigid elongate canister having an inlet and an outlet for fluid, at least two fluid-permeable partitions dividing the space within the canister into several compartments, each of which extends substantially the full length of the canister, and a packing of magnetizable material disposed between the partitions. The form and disposition of the canister, the partitions and the packing material is such that the fluid flows from the inlet, through the packing material in a direction transverse to the axis of the canister, to the outlet, and the linear velocity of the fluid decreases as it passes through the packing material. As the fluid passes through the separating chamber, magnetizable particles within the fluid are magnetized and attracted to the packing material.

Abstract: A method of lining a pipe with settable material including the steps of arranging the pipe with its longitudinal axis inclined at an angle to the horizontal, introducing a selected amount of liquid material into the pipe at a predetermined rate so that the liquid material flows down along the pipe, shifting the pipe to a horizontal position and spinning the pipe about its axis to distribute the material, spinning continuing until the material has set. The method is particularly applicable for lining pipes with polyurethane. For pipes with end flanges end faces of the lining material can be formed integral with the lining.

Abstract: A method of lining a pipe with thermosetting synthetic plastics material including the steps of arranging the pipe with its longitudinal axis inclined at an acute angle to the horizontal, introducing liquid lining material into the pipe at a predetermined rate for a predetermined time, shifting the pipe to a horizontal position shortly before or at the completion of introduction of the liquid material, spinning the pipe about its axis and blowing hot air axially through the pipe after spinning has started but before the lining material has set thereby to remove entrained air bubbles. The method is particularly applicable for lining pipes with polyurethane, especially pipes with end flanges and covers to form an end face of the lining material.

Abstract: A method and apparatus for temporarily straightening and spinning of pipes wherein at least three sets of rollers are used, each set including four rollers of which two are rotatably mounted in fixed locations and the other two of which are movable by hydraulic driving means, one or more of the fixed location rollers being drivable; collars, each made of three hinged segments, are used around the pipe, which collars are circumferentially stronger than the pipe wall; by pressing the movable rollers against the collars, the collars are held closed and the pipe is held straight while being spun. The invention is particularly although not exclusively applicable for use in a process of lining of pipes.

Abstract: There is disclosed a device suitable for obtaining from a fluid mixture of first and second component materials a quantity thereof which contains a fixed weight of said first component material, and an apparatus for determining the proportion by weight of particles of a particulate solid material in suspension in a liquid which are larger than a given size. The apparatus comprises (i) means for delivering a quantity of the suspension containing a fixed weight of particulate solid material, (ii) means for separating from said quantity of suspension substantially all the solid particles larger than said given size; and (iii) means for determining the weight of said solid particles which are larger than said given size.