Porosity - Porous Filter Disc
From Sintered Disc
Filtering with Porous Filter Disc made of Quartz Glass -Sintered Discs. Quartz glass filters have multiple applications for analytical work in laboratories, in special-design laboratory equipment, and as component parts in technical apparatus. The purpose of filtration is separation of parts with certain size from liquids or gases. We use filtration in chemical works, in order to separate the fall-out from the liquids. It is depending on the fall-out size, which filters are to be used. The finest filters (manufactured of quartz glass) are that fine, that even the bacteria get separated through such filters. There are 5 porosity grades from quartz glass filters.
The purity, chemical resistance and its high thermic endurance of quartz glass are realy its character and it allows us to apply it in great variety.
Innovative and powerful manufacturing secures the quality of the products during production and guarantees uniform properties even for the highest demands and exacting applications.
Next to a large variety of standard types, special designs also could be adjusted to your specific requirements.
According to their pore sizes, quartzglass filters are divided into porosity grades from 0 to 5. Table 1 shows the porosity ranges and their main fields of application. The pore sizes indicated always refer to the largest pore in the disc. This also indicates the diameter of the particles which are only retained during filtration. Porosities are determined using the Bechhold bubblepressure method which has often been described in literature. To achieve rapid filtration it is necessary to produce as many “passage” pores as possible without dead-ends or enclosed hollow spaces. The practical advantages stem from the well established properties of quartzglass and the special manufacturing techniques used in sintering the quartzglass particles, which are the starting material for filter discs.
An essential condition for successfuly working with quartzglass filters is the selection of the correct porosity. Table 1 snows six porosity ranges and indicates their main fieds of application. In selecting suitable filtration apparatus it should be remembered that the nominal maximum pore size should be slightly less than the size of the smallest particles to be separated. This prevents these particles from entering the pores. It also permits highest possible flow rates without making cleaning unnecessary difficult. This is specially important in the separation of fine-grained insoluble solid particles such as silicates and graphite.
Quartzglass filter apparatus of porosities 3 or 4 is used almost exclusively in quantitative analysis. Different porosities are sometimes recommended for the same substances. This is explained by the fact that differing precipitation techniques for gravimetric analysis often produce different particles sizes. In case of doubt, porosity 4 is preferred as it will always allow quantitative separation of the precipitate. Porosity 3 however, has proved itself completely satisfactory in all cases for substances such as silver chloride and nickel dimethylglyoxime.