Presentation on theme: "Filtration Simple crucible Gooch filter crucible : fritted glass(= sintered glass) funnel porosity : f (=fine), m (=medium), c (=coarse) Aspirator or vacuum."— Presentation transcript:
Filtration Simple crucible Gooch filter crucible : fritted glass(= sintered glass) funnel porosity : f (=fine), m (=medium), c (=coarse) Aspirator or vacuum pump Trap Mother liquor Filtrate Decantation is the process of pouring a liquid gently so as to not disturb a solid in the bottom of the container. Rubber policeman Squirt bottle
Train for vacuum filtration Vacuum filtration with a Gooch crucible that has a porous (fritted) glass disk through which liquid can pass. Suction can be applied by the vacuum system or by an aspirator that uses flowing water to create vacuum. The trap prevents backup of tap water from the aspirator into the suction flask. Alternatively, the trap prevents liquid in your suction flask from being accidentally sucked into the vacuum system.
Ashless filter-paper : Specially treated filter-paper (pulps treated by using 6M HCl, HF) that leaves a negligible residue(=incombustible matter) after ignition. Ash 0.2mg when a filter-paper(I.D. 11cm) has been incinerated.
(Left) Filtering a precipitate. The conical funnel is supported by a metal or wood ring attached to a ring stand. (Center) Washing by decantation. (Right) Transferring the precipitate. Creeping is a process in which a solid moves up the side of a wetted container or filter paper.
Folding filter paper for a conical funnel. (a)Fold the paper in half. (b)Then fold it in half again. (c)Tear off a corner to allow better seating of the paper in the funnel. (d)Open the side that was not torn when fitting the paper in the funnel.
Method for folding and seating a filter paper The filtering operation. Washing by decantation and transferring the precipitate
Pipets and sylinder. Pipets and syringes TC 20 o C = calibrated to contain the indicated volume at 20 o C (ambient temperature) E : eingu TD 20 o C = calibrated to deliver the indicated volume at 20 o C A : ausgu The coefficient of expansion for dilute aqueous solution: 0.025%/ o C V T1 = V T2 + 0.00025(T 1 -T 2 )V T2 where T 1 > T 2 Transfer pipet Don’t blow out the last drop Measuring (Mohr) pipet Microliter pipet (Eppendorf)
Examples of pipets a. Volumetric (TD) b. Mohr : Measuring (TD) c. Serological : Measuring (TD) d. Eppendorf micropipet (TD) e. Ostwald-Folin (TD) f. Lambda (TC)
Safety rubber bulb filler A : press on valve A and squeeze bulb S : Insert pipet into liquid sample. Press on valve S. Suction draws liquid to desired level. E : Press on valve E to expel liquid sample. To deliver the last drop, maintain pressure on valve E, cover E inlet with middle finger, and squeeze the small bulb. E A S 1234
Transfer pipet. Measuring (Mohr) pipet. Microliter pipet with disposable plastic tip. Volume selection dial of microliter pipet. Repeater pipet, which can deliver preset volumes between 10 L and 5 mL to 48 times at 1-s intervals without refilling.