Process of preparing virtually cadmium-free calcium sulphate and calcium sulphate prepared according to this process
CA 1320034 C · Owner: Spijker, Ruud · Inventors: Witkamp, Geert J.; Tjioe, Tjay T.; Spijker, Ruud
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Virtually cadmium-free calcium sulphate is produced in the preparation of a liquid medium containing phosphoric acid which, comprises digestion with a mineral acid of cadmium-containing phosphate rock and separation from the liquid medium containing phosphoric acid of at least a portion of the calcium in the phosphate rock after precipitation by means of a solution containing sulphate ions in the form of calcium sulphate, in which process halogen ions are present in an amount of 50-20.000 ppm during precipitation of the calcium sulphate to be separated.
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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 July 13, 1993. A Canadian patent filed before October 1, 1989 lasted 17 years from grant, so its term ended July 13, 2010.
- 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.