Hazard
Not toxic if ingested, inhaled silica dust can
cause silicosis; carcinogen.
Potential Exposure
Diatomaceous earth is used as
a filtering agent and as a filler in construction materials,
pesticides, paints, and varnishes. The calcined version
(which has been heat treated) is the most dangerous and
contains crystallized silica, and should be handled as silica.
See also other entries on silica
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical has been
inhaled, remove from exposure, begin rescue breathing
(using universal precautions, including resuscitation mask)
if breathing has stopped and CPR if heart action has
stopped. Transfer promptly to a medical facility.
Shipping
This material is not singled out by DOT
in its
Performance-Oriented Packaging Standards.
Incompatibilities
Silica, amorphous is a noncombustible solid. Generally unreactive chemically. Incompatible with fluorine, oxygen difluoride, chlorine trifluoride. Soluble in molten alkalis and reacts with most metallic oxides at high temperature.
Chemical Properties
Amorphous silica, the noncrystalline form of SiO2, is a transparent to gray, odorless, amorphous powder
Chemical Properties
Diatomaceous earth is a transparent to gray,
odorless amorphous powder.
Chemical Properties
white crystals or powder
Waste Disposal
Sanitary landfill.
Physical properties
Colorless amorphous (i.e., fused
silica) or crystalline (i.e., quartz)
material having a low thermal
expansion coefficient and
excellent optical transmittance
in far UV. Silica is insoluble in
strong mineral acids and alkalis
except HF, concentrated H3PO4, NH4 HF2 , concentrated alkali metal hydroxides. Owing to its
good corrosion resistance to
liquid metals such as Si, Ge, Sn,
Pb, Ga, In, Tl, Rb, Bi, and Cd, it
is used as crucible container for
melting these metals, while silica
is readily attacked in an inert
atmosphere by molten metals
such as Li, Na, K Mg, and Al.
Quartz crystals are piezoelectric
and pyroelectric. Maximum
service temperature 1090°C.
Definition
ChEBI: A silicon oxide made up of linear triatomic molecules in which a silicon atom is covalently bonded to two oxygens.
Agricultural Uses
Silica is silicon dioxide, one of the most abundant
materials on the earth's crust. Quartz is an example of
silica. It is used as a filler in fertilizers, and also, in the
manufacture of glass, ceramics, abrasives, rubber and
cosmetics.
Purification Methods
Purification of silica for high technology applications uses isopiestic vapour distillation from concentrated volatile acids and is absorbed in high purity water. The impurities remain behind. Preliminary cleaning to remove surface contaminants uses dip etching in HF or a mixture of HCl, H2O2 and deionised water [Phelan & Powell Analyst 109 1299 1984].
Derivatives
Precipitated silica is obtained like silica gel by acidifying an aqueous solution of sodium
silicate. Precipitated silica is used as filler in rubber for automobile tires and reinforcement
particulate in elastomers, and as a flatting agent in paints and coatings for improving the flatness of coatings.
