Title of Invention	A PROCESS FOR PREPARING ALPHA CRYSTALLINE FERRIC OXIDE
Abstract	This invention relates to a process of preparing crystalline ferric oxide. Aqueous solution of an alkali is slowly added to an aqueous solution of a ferric salt. The yellowish brown precipitate is washed dried, powdered and then further dried and ground to obtain ferric oxide having crystalline structure.

Full Text

This invention relates to a process for preparing crystalline ferric oxide. Ferric oxide having crystalline structure is found to exhibit excellent catalytic activity and is found to be a reliable burn rate modifier for composite solid propellants using ammonium perchlorates as an oxidizer. The object of this invention is prepare ferric oxide with crystalline structure by a simple, easily adaptable and repeatable process. The ferric oxide obtained by this process shows higher catalytic activity which is attributed to its higher surface area and low particle size. The process of preparing ferric oxide with crystalline structure consists of the following steps. An alkaline solution selected from sodium, potassium or ammonium hydroxide is gradually added to a dilute aqueous solution of a ferric salt slowly under constant stirring. The reaction is carried out at ambient conditions. Addition of the alkali is stopped when the reaction mixture becomes neutral. Ultra fine yellowish brown precipitate formed is allowed to settle, the supernatant liquid is decanted and the precipitate is repeatedly washed with distilled water to free it from traces of alkali, ferric ions and the anions of the ferric salt. The precipitate is then filtered and oven dried at a low temperature of about 90 to remove moisture content therefrom. During this drying step care must be taken to avoid caking of the product. Drying for a period of 12 hours is found sufficient. The dried powder is ground to obtain a powder free of agglomerates and is then sieved using a 150 mesh sieve. The sieved material is further heated in an air oven at a temperature ranging from 10-20 hours. The dark brown powder is again pulverized and sieved using a 150 mesh sieve and is immediately packed in air tight containers to avoid moisture pickup and caking. Any water soluble ferric salt can be used for this purpose. Thus, a process for preparing oL crystalline ferric oxide according to this invention comprises adding an aqueous solution of an alkali to an aqueous solution of ferric salt, under ambient conditions to obtain an yellowish brown precipitate, separating washing, drying and subsequently grinding said precipitate to a powder and further drying said powder to obtain ferric oxide having crystalline structure. The process will hereinafter be described with reference to the following examples. Example I 500 gm of ferric nitrate of above 98% purity is dissolved in 1.5 litre of distilled water. Suspended impurities and insoluble are removed therefrom by filtration. Dilute aqueous ammonia of 4-5% strength is prepared by diluting 350 ml of 25% of ammonia solution with distilled water to get 1.8 litres. A three necked flask or a beaker of required capacity is fitted with a mechanical stirrer with speed control and the aqueous ferric nitrate solution Is taken in the said reaction vessel. Ammonia solution is gradually added thereto with constant stirring over a period of 3-4 hours. Fine yellowish brown precipitate formed is allowed to settle, the supernatant liquid decanted and the precipitate washed repeatedly till free of alkali or anion and the pH is neutral. This precipitate is then filtered under vacuum and washed again with distilled water. This precipitate is then transferred to a tray and dried at a temperature of about 90^C for 5-10 hours to remove moisture content. The dried precipitate is ground and sieved with a 150 mesh sieve which is subsequently heated to 200-240^C for 10-20 hours to obtain the desired level of surface area. This is further powdered and the fine ferric oxide is sieved using a 150 mesh sieve. The sieved powder is packed and sealed to protect it from moisture pickup and agglomeration. Example II The reaction is repeated with a solution of sodium or potassium hydroxide instead of ammonia. 150 gm of sodium hydroxide of 98% purity is dissolved or 208 gm of potassium hydroxide of 98% purity is dissolved in 3 litres of distilled water and the reaction carried out as stated in Example I to get ferric oxide of ^ crystalline structure. Though this process has been described herein above with reference to a specific embodiment, alterations and modifications known to persons skilled in the art are not beyond the scope of the appended claims: * We claim; 1- A process for preparing o4 crystalline ferric oxide comprising adding an aqueous solution of an alkali to an aqueous solution of ferric salt under ambient conditions to obtain an yellowish brown precipitate, separating, washing, drying and subsequently grinding said precipitate to a powder and further drying send powder to obtain ferric oxide having ©6 crystalline structure. 2. The process as claimed in claim 1 wherein said aqueous solution of alkali is a solution of ammonium hydroxide, sodium hydroxide or, potassium hydroxide. 3. The process as claimed in claims 1 and 2 wherein said alkaline solution is added gradually to said ferric salt solution under constant stirring over a period of 3-4 hours. 4. The process as claimed in claims 1-3 wherein the precipitate is washed free of anions and alkali till the pH is neutral. 5. The process as claimed in claims 1-4 wherein the precipitate is initially dried at a temperature of about 90^0 for a period of 5 to 10 hours. 6. The process as claimed in claim 5, wherein the dried powder is ground to a mesh size of 150. * 7. The process as claimed in claims 1-6 wherein the powdered precipitate is subjected to further drying at 220-240°C for a period of 10-20 hours. 8. The process as claimed in claim 7 wherein said further dried precipitate is further powdered, sieved using 150 mesh sieve and subsequently packed and sealed to prevent moisture absorption. 9. A process for preparing of crystalline ferric oxide substantially as herein described.

Documents:

547-mas-1999-abstract.pdf

547-mas-1999-claims filed.pdf

547-mas-1999-claims granted.pdf

547-mas-1999-correspondnece-others.pdf

547-mas-1999-correspondnece-po.pdf

547-mas-1999-description(complete)filed.pdf

547-mas-1999-description(complete)granted.pdf

547-mas-1999-form 1.pdf

547-mas-1999-form 26.pdf

547-mas-1999-form 4.pdf