March/April 2007

Mineral flotation and patentable utility

By J. Pivnicki

Mineral flotation is a commonly used method to separate a mineral from a gangue material and produce a mineral concentrate. The mineral feed to a flotation device is ground quite finely, and is usually treated with flotation reagents, which improve the mineral separation process.

In 1925, this method of mineral flotation with reagent assistance was in its infancy and Mineral Separation North America Corporation was issued Canadian Patent CA 247,576 1 (the ’576 patent) entitled “Froth Flotation Concentration of Ores.” Mineral Separation subsequently licenced their patent to many of the biggest mining companies of the day, including International Nickel Co. and Hudson Bay Mining & Smelting.2 However, several other Canadian mining companies, including Noranda Mines, refused to take out licences. Mineral Separation sued Noranda Mines for infringement of their patent. In their defence, Noranda Mines contended that the patent was invalid, and therefore, could not be infringed.

This landmark case, which was first heard in 1947, was appealed all the way to the Judicial Committee of the Privy Council of the House of Lords in 1952, which was the highest Canadian judicial body at the time.

The ’576 patent described a flotation process where “xanthates” or “sulphur derivatives of carbonic acid” were used to “greatly increase the efficiency of the froth-flotation process.” The claims of the patent (i.e. the portion of the patent that defines the legal boundaries of the invention protected by the patent) were directed to “a process for concentrating ores” and an “improvement in the concentration of minerals by flotation” using the described xanthates. The claims of the ’576 patent covered the use of all types of xanthates as the flotation reagent, and therefore included cellulose xanthates that were known to hinder, and not enhance, mineral flotation and thus did not do what was promised by the patent.

The Judicial Committee of the House of Lords ruled that the claims of the ‘576 patent were invalid, because they were not operable and did not make good their promise to improve flotation of minerals when cellulose xanthates were used.

In Canada, the three main requirements for patent validity are: novelty, non-obviousness, and utility. These three requirements are the principal foundations on which patent validity is built; the lack of any one of these requirements will invalidate the patent.

For a patent to have utility, it must be operable. The description must be sufficiently detailed and must “correctly and fully describe the invention” 3 such that it allows a skilled person to use the invention.

The subject matter of a patent lacks utility if the invention either does not work at all or the description promises something that the invention does not do.

John Pivnicki is a patent agent-in-training at Ogilvy Renault.

1 The CA 247,576 patent is available online at Canadian Intellectual Property Office:

2 Mineral Separations North American Corp. v. Noranda Mines Ltd. [ (1947 (Ex. Ct.), 12 C.P.R.; (S.C.C) 12 C.P.R. 99; 1952 (P.C.) 15 C.P.R. 133].

3 The Patent Act ( R.S., 1985, c. P-4 ), Section 27(3)(a), available at CIPO:

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