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Analytical test methods
ISO 9277 / PA 0100 / ACM-107 This test method describes the determination of the total specific external and internal surface area of disperse or porous solids by measuring the amount of physically adsorbed gas according to the method of Brunauer, Emmett and Teller (BET method). The resulting specific surface area is a multipoint BET value and is expressed in m2/g.
ISO 3262-20 / PA 0600 The carbon content in fumed silica and fumed oxides is obtained by the oxidation of carbon in a sample through combustion and the resulting CO2 measured by infrared (IR) detectors.
ISO 787-2 / PA 0300 / ACM-101 The determination of the amount of moisture or volatile compounds adsorbed by the surface of pyrogenic oxides is obtained by drying the sample in an oven for two hours at 105°C.
ISO 3262-20 / PA 0400 The loss on ignition is determined at 1000°C at which the chemically bonded water as well as the physically bonded water is lost.
PA 0420 Pyrogenic oxides which surfaces have been modified with non-hydrolyzable organic molecules, cannot be wetted by water. However, these hydrophobic dispersed silicas and other fumed oxides can be wetted using a methanol/water mixture. The content of methanol in such mixture - in weight-% - is a measure for the degree of hydrophobicity and uniformity of treatment of the modified fumed oxide.
ISO 787-9 / PA 0200 / PA 0210 / ACM-102 AEROSIL® is a highly dispersed colloidal silica powder which is produced by a "high-temperature hydrolysis process" and thus has a very high grade of purity. The gaseous hydrogen chloride can be separated from the stream of Si02. The pH-value is a measure for the degree of deacidification of AEROSIL® and indicates physical-, chemical- and application specific properties of hydrophilic and hydrophobic AEROSIL® products. This method can be applied to hydrophilic and hydrophobic AEROXIDE® products and special oxides as well.
ISO 3262-20 / PA 0501 / ACM-118 As the silicon dioxide content of AEROSIL® is very high, the impurities need not be removed beforehand. To determine the SiO2-content, the sample is treated with a sulphuric acid/ hydrofluoric acid mixture. Where samples are older than 10 days or for hydrophobic AEROSIL® in general, the samples are ignited and weighed beforehand and then treated with the sulphuric acid/hydrofluoric acid mixture. As the generated silicon tetrafluoride is volatile, the SiO2 content can be determined by the loss in weight.
ISO 787-11 / PA 0701 / ACM-104 The tamped density of powders (often called tapped density) depends upon density, particle shape, and particle size. It allows conclusions to be drawn on e.g. the required size of packaging and the regularity of deliveries. The tamped density is equal to the ratio between the mass and the volume of a powder after it has been tamped in the tapping volumeter under stipulated conditions. The tamped density is specified in g/cm3 in compliance with ISO 787-11. However, we specify the value in g/l due to the often low tamped density of synthetic pyrogenic oxides.