Process for purifying phosphoric acid for electrical semiconductor use
CA 1297266 C · Owner: Hall, Richard E. · Inventors: Jueneman, Frederic B.; Hall, Richard E.; Zeh, Peter H.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Phosphoric acid is treated to remove and/or tie up heavy metals and antimony to enable the acid to be used in electrical semiconductor applications by reacting the acid with hydrogen sulfide and with hydrogen peroxide in separate treating steps. The hydrogen sulfide precipitates metal sulfides which are separated from the acid, and the hydrogen peroxide oxidizes dissolved antimony so that it is tied up and does not post-precipitate in the acid after removal of the metal sulfides.
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Granted March 17, 1992. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended March 17, 2009.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.