Rice husk is an agricultural residue easily available in rice producing countries. India is a major rice producing country, and the husk generated during milling is mostly used as a fuel in the boilers for processing paddy, producing energy through direct combustion & or by gasification. The rice husk contains about 75% organic volatile matter & the balance 25% of the weight of this husk is converted into ash during the firing process, is known as rice husk ash (RHA). This RHA in tern contains around 85%–92% amorphous silica. Silica is one of the valuable inorganic chemical compounds. It can exist in gel, crystalline and amorphous forms. It is the most abundant material in the earth’s crust. Silica is the major constituent of rice husk ash. With such a large ash content & silica content in the ash it becomes economical to extract silica from the ash, which has wide market & also takes care of ash disposal. Precipitated Silica (also called particulate silica) is composed of aggregates of ultimate particles of colloidal size that have not become linked in massive gel network during the preparation process. It is an amorphous form of silica; the word amorphous denotes a lack or crystal structure, as defined by x-ray diffraction. Early interest in amorphous silica was purely academic. Amorphous silica can be broadly divided into three categories. Vitreous silica or glass made by fusing quartz, Silica made indicating either amorphous or crystalline silica with high speed neutrons & Micro amorphous silica. Micro amorphous silica includes sols, gels powders & porous glasses, all of which are composed of ultimate particles or structural units less than 1/um in diameter. These silica have high surface area, generally greater than 3m2/g. Micro amorphous silica can be further divided into micro particulate silica microscopic sheets & fibers & hydrated amorphous silica. .Gynogenic silica’s are formed at high temperature by condensation of SiO2 from the vapor phase, or at lower temperature by chemical reaction in the vapor phase followed, by condensation. Silica formed in an aqueous solution can occur as sols, gels or particles. A gel has a three-dimensional, Continuous structure, where as a sol is a stable dispersion of fine particles. Macroscopic particles are formed by aggregation of smaller particles from either a gel or so. Amorphous silica is precipitated from super saturated solution obtained by concentrating an under saturated solution a hot saturated solution, or generating Si(OH)4 of silica ester SiH4, SiS2, SiCl4 or Si. Precipitated Silica soluble silicate solutions are of fine controlled particle size & porous in nature. Precipitated silica powders have a more open structure with higher volume than dried pulverized gels. The physical & chemical properties or precipitated silica vary according to the manufacturing process. Ultimate & aggregate particle size in silica’s precipitated from solution can be varied by reinforcement & control of suspension pH, temperature & salt content. The particle size in gynogenic silica’s is controlled by combustion conditions. The surface area as determined by nitrogen adsorption is a function of particle size. USES AND APPLICATION Precipitated silica is used as filler for paper & rubber as a carrier & diluents for agricultural chemicals, as an anti caking agent, to control viscosity & thickness and as a cleansing agent in toothpastes & in cosmetics. Precipitated silica also finds its applications as anti caking agents in food industry & as thermal insulators. Precipitated silica is perhaps the best not black filler and reinforcing agent used in rubber industry especially for the production of silicon rubber. The distinguishing feature of the growth of precipitated silica industry in India is that it has classifiably flourished in the small-scale sector. Readily available new materials low capital investment & high rates of return offer a distinct advantage to the small-scale manufacturers to venture into this field. MARKET SURVEY Precipitated Silica is used as filler for paper & rubber as a carrier & diluents for agricultural chemicals, as an anti caking agent, to control viscosity & thickness and as molecular sieves. So, we can better understand the growing demand of precipitated silica by seeing the demand of the following industries.Silicon is a unique material. Its abundance is one of the reasons it is used for a wide range of purposes. One of the most important uses of silicon is as a core element of microchips. To manufacture microchips, the microelectronics industry requires silicon with an impurity level of 10–11. Since silicon forms a stable compound with oxygen (silicon oxide, SiO2), the deoxidization of silicon oxide needed to reach this high level of purity consumes a substantial amount of energy, which, in turn, affects the environment through emissions of carbon dioxide (CO2).Bulk silicon wafers used at the beginning of the integrated circuit making process must first be refined to "nine nines" purity (99.9999999%), a process which requires repeated applications of refining technology. The silicon demand by the PV cell industry can be estimated using the available amount of silicon in combination with the amount of silicon needed to produce 1 MWp of solar cells. Global production of rice, the majority of which is grown in Asia is approximately 550 million tonnes/year. This is generated at a rate of about 20% of the weight of the product rice, or some 110 million tonnes per year globally. The husk in turn contains between 15 and 20% of mineral matter the majority of which is amorphous silica. There is a growing demand for finely divided amorphous silica in the production of high strength, low permeability concrete, for use in bridges, marine environments, and nuclear power plants. This market is currently filled by silica fume. Limited supply and high demand has pushed the price of silica fume to as much as US$ 1,000/tonne in some market. Rice husk has the potential to generate 16.5 to 22 million tonnes of ash containing over 90% amorphous silica that could be used as a substitute for silica fume. The husk has energy content of about 14 GJ/tonne so that the energy potential worldwide would be some 1.5 billion GJ/year, which at US$ 5/GJ would have an annual value of US$ 7.5 billion. This amount of energy is equivalent to over 1 billion barrels of oil per year. PRESENT MANUFACTURERS Anand Engineers Pvt. Ltd. Anand Lubricants Pvt. Ltd. Camco Multi Metal Ltd. Elofic Industries Ltd.