Gravity filtration filter cone

Extremely wet solids (solid floating in water). Set up a gravity filtration (see Gravity Filtration ) and filter the liquid off of the solid. Remove the filter paper cone with your solid product, open it up, and leave it to dry. Or remove the solid and dry it on fresh filter paper as above. Use lots of care though. You don t want filter paper fibers trapped in your solid. 

The key to successful gravity filtration is the fluted filter paper. A fluted filter paper decreases the area of contact between the filter paper and the funnel, thus allowing rapid filtration. If you use traditional cone-folded filter paper, note that all sides of the paper are touching the sides of the funnel and on half the filter paper the liquid has to pass through three thicknesses of paper, all of which slow the rate of filtration. Slow filtration can lead to disaster in hot filtration during recrystallization (p. 100). 

The filter cone is prepared as indicated in Figure 8.1. It is then placed into a funnel of an appropriate size. With filtrations using a simple filter cone, solvent may form seals between the filter and the funnel and between the funnel and the lip of the receiving flask. When a seal forms, the filtration stops because the displaced air has no possibility of escaping. To avoid the solvent seal, you can insert a small piece of paper, a paper clip, or some other bent wire between the funnel and the lip of the flask to let the displaced air escape. As an alternative, you can support the funnel by a clamp fixed above the flask rather than placed on the neck of the flask. A gravity filtration using a filter cone is shown in Figure 8.2. 

Tanks with conical bottoms discharge cakes by gravity and those with dished bottoms have a spade that rakes and conveys the cake towards the outlet. Hence, the conical types require more headroom as compared to the dished type having the same filtration area. Conical tanks also have often an additional scavenging plate at the lower part of the cone to filter the residual slurry heel that remains below the main plates. The slurry heel that remains at the very bottom of the tank is removed through a special dip pipe to avoid discharging a wet cake. To facilitate better cake... 

Add 120 g. of powdered potassium bromide to 200 ml. of water. Place the container in cold water, and slowly add 90 ml. of cone, sulfuric acid (1.7 mols). The temperature should not go appreciably above 75°C. otherwise a small amount of free bromine may be formed. However, the formation of a small amount of bromine is not particularly serious, since it will come over with the distillate boiling between 100 to 115°C. Cool the solution to room temperature, and remove the potassium acid sulfate by filtering through a hardened filter paper in a Buchner funnel. Place the filtrate in a 500-ml. distilling flask connected to a water condenser fitted with an adapter, and heat over a wire gauze. If the presence of 0.01 to 0.015 per cent of sulfate ion is not objectionable, reserve the distillate that starts to come over 1° below the temperature of the constant-boiling mixture. The distillation should be stopped when the temperature drops. The specific gravity of the solu-... 

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