The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 08, 1994
Filed:
Oct. 01, 1992
Applicant:
Inventors:
Tadahiro Ohmi, Miyagi, JP;
Hiroyuki Harada, Tokyo, JP;
Nobuhiro Miki, Osaka, JP;
Toshiro Fukutome, Osaka, JP;
Matagoro Maeno, Izumi, JP;
Norio Terasawa, Tokyo, JP;
Yoshihiro Eto, Kanagawa, JP;
Masahiro Sakata, Tokyo, JP;
Assignee:
Kurita Water Industries, Ltd., Tokyo, JP;
Primary Examiner:
Int. Cl.
CPC ...
C01F / ;
U.S. Cl.
CPC ...
423163 ; 423490 ;
Abstract
Calcium fluoride with high purity of very small content of unreacted calcium carbonate and silica is recovered from an etchant mainly composed of hydrogen fluoride or hydrogen fluoride and ammonium fluoride. The etchant is reacted with calcium carbonate with transfer directions of the etchant and calcium carbonate being controlled within a composition region in which mole equivalent ratio of ammonium fluoride/hydrogen fluoride is specified.