A filter funnel is used in laboratories to separate the liquids from the solids. The process is done via filtering. They are used for preparative chemistry, qualitative inorganic analysis and other experiments.
Filter Funnel Size
The dimensions of the filter funnel vary. Among the most widely used capacities are 50, 75, 125, 500, 1,000 and 4,000 ml. Their height varies as well; the 50 ml capacity filter funnel is about 130 mm high as is the 75 ml. The 125 ml is 140 mm tall and the 500 ml is 200 mm high.
The 1,000 ml is about 320 mm high and the 4,000 ml is 400 mm. The 50 ml funnels have a diameter of 35 mm while the 75 ml has a disk diameter of 45 mm. The 125 ml funnel has a diameter of 60 mm. The 1,000 ml funnel has a disk diameter of 120 ml. For the 4,000 ml the diameter is 175 mm. There are other filter funnel sizes available.
Features and Characterizes
For the filtering to work, a filter paper shaped like a disk is folded in the cone. This is put inside the funnel. The liquid and solid suspension is poured into the funnel.
The solid particles are left on the paper because they are too large to pass the paper. The smaller liquid particles are able to go through. The liquid then goes into a container placed under the funnel. This generates a filtrate.
The filter paper is discarded after it is used; they are only used one time. If the liquid is important, it will be retained. In some cases, the filtrate and the paper residue are both preserved for examination.
Whatever the filter funnel sizes are, care must be taken when choosing the filter paper. If the pores are small, liquid like oil may get stuck. The dimensions of the filter funnel will be based on the suspension volume that has to be filtered.
Most of these filter funnels are constructed from plastic. If the solvent needs glass, glass filter funnels can be used. There are some filter funnels made from galvanized steel or polyethylene.
These come with a plastic or brass filter. They are usually used in car repair shops and in some workshops. In these instances, they are used for removing debris from the oil. They are also used for lubrication. These types have a reusable screen.
Inverting the funnel and tapping the surface can clean it up. Alternatively, it can be popped up and washed. This will keep liquids from spilling.
Note: because they can be used for making narcotics, some states in the US now demand permits before one can buy these. Be sure to check out the laws in your area before buying.
Because the filter funnel sizes vary, you should check the product specs carefully. You should also follow the instructions on how to use it. However, for the most part the process is the same so you will have little problems using it.