Silica gel

Silica gel

Identifiers
CAS Number	112926-00-8 [1][2][3] Y 1343-98-2 (Silicic acid) Y
ChemSpider	none
ECHA InfoCard	100.065.880
UNII	Y6O7T4G8P9 Y
CompTox Dashboard (EPA)	DTXSID9029851 DTXSID0051285, DTXSID9029851
Properties
Chemical formula	SiO2
Molar mass	60.08 g/mol
Appearance	Transparent beads
Odor	Odorless
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other liquids, or may be filled by gas or vacuum. In the last case, the material is properly called silica xerogel.

Silica xerogel with an average pore size of 2.4 nanometers has a strong affinity for water molecules and is widely used as a desiccant. It is hard and translucent, but considerably softer than massive silica glass or quartz, and remains hard when saturated with water.

Silica xerogel is usually commercialized as coarse granules or beads, a few millimeters in diameter. Some grains may contain small amounts of indicator substance that changes color when they have absorbed some water. Small paper envelopes containing silica xerogel pellets, usually with a "do not eat" warning, are often included in dry food packages to absorb any humidity that might cause spoilage of the food.

'Wet' silica gel, as may be freshly prepared from alkali silicate solutions, may vary in consistency from a soft transparent gel, similar to gelatin or agar, to a hard solid, namely a water-logged xerogel. It is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles.^[4]