LIQUID/LIQUID, LIQUID/GAS OR GAS/GAS SEPARATION Method General operations by centrifugal force, using centrifuges or free-vortex apparatus using magnetic or electrostatic effect Apparatus General operations by centrifugal force, using centrifuges or free-vortex apparatus , using magnetic or electrostatic effect SOLID/LIQUID OR SOLID/GAS SEPARATION Method General operations by centrifugal force using centrifuges or free-vortex apparatus using magnetic or electrostatic effect Apparatus General operations by centrifugal force using centrifuges or free-vortex apparatus , using magnetic or electrostatic effect SOLID/SOLID SEPARATION Method Dry methods material in bulk Individual sorting Screening, sifting, pneumatic sorting using pneumatic tables or jigs by magnetic or electrostatic effect by centrifugal force using centrifuges or free-vortex apparatus Wet methods General operations flotation, differential sedimentation screening Combinations Dry methods - wet methods Apparatus Dry methods material in bulk Individual sorting Screening, sifting, pneumatic sorting using pneumatic tables or jigs by magnetic or electrostatic effect by centrifugal force using centrifuges or free-vortex apparatus , Wet methods General operations flotation, differential sedimentation screening Combinations Dry methods - wet methods In this subclass, the following expression is used with the meaning indicated: "writing implements" covers pens, pencils, crayons, chalks or like markers for writing or drawing. IMPLEMENTS WITH CORES Without mechanisms With mechanisms Accessories , IMPLEMENTS USING INK Without reservoir With reservoir , , Nibs; filling devices; caps , ; ; Manufacture, maintenance , SELECTING, PROJECTING, RETRACTING OR LOCKING WRITING UNITS MULTIPLE-POINT WRITING IMPLEMENTS COMBINATIONS Of writing implements with other articles , This subclass does not cover devices used for both teaching and facilitating writing or drawing, which are covered by group . ARTICLES FOR WRITING OR DRAWING UPON Boards or tablets Underlays Drawing-boards AIDS FOR DRAWING Straight lines Circles Other curves Means to prevent slippage Other figures ATTACHMENT TO HANDS OR ARMS BLOTTERS ACCESSORIES FOR Rubbing or erasing Cleaning blackboards or slates Sharpening pencils or leads INK RECEPTACLES; INK STANDS ; FIXING SEALS; INSERTING DOCUMENTS INTO, CLOSING, OR OPENING, ENVELOPES ; , , PAPER-WEIGHTS; DEVICES FOR APPLYING LIQUIDS; STAMP DISPENSERS; DRAWING-PINS OR THUMB-TACKS; OTHER ACCESSORIES ; ; ; ;