Production of sodium hydroxide
CA 2116017 C · Owner: Smith, James W. · Inventors: Tran, Hoc Nghia; Smith, James W.
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Sodium hydroxide is formed from sodium sulphate by a three step operation comprising converting the sodium sulphate to sodium sulphide, converting the sodium sulphide to sodium bicarbonate, and converting the sodium bicarbonate to sodium hydroxide. The operations preferably are effected in conjunction with a bleached kraft pulp mill operation, so as to utilize by-product sodium sulphate from chlorine dioxide generation to produce useful sodium hydroxide as sulphur without co-producing chlorine.
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
- Filed August 20, 1992 and granted April 27, 1999. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended August 20, 2012.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by August 20, 2014.
- 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.