A recent decision (Calix Limited v Grenof Pty Ltd[1]) from the Federal Court of Australia provides a cautionary tale to patent applicants and patent attorneys regarding the complexities in drafting a patent specification, and highlights the importance of the written description in supporting the claimed invention.

Background and claims

Calix was the owner (patentee) of Australian Standard Patent No 2014339743 (AU’743), directed to the production of hydroxide slurries for industrial purposes. Calix alleged that Grenof (and subsequently Aquadex) infringed AU’743 by manufacturing, supplying or offering to supply hydroxide slurry under the name Phodine and Phodine Plus (and that Aquadex had also infringed by supply of hydroxide slurry, also under the name Phodine). Grenof and Aquadex admitted that those products were made using the same process (Grenof process).

Grenof filed a cross-claim seeking revocation of claim 1 of AU’743 on the grounds that the claimed invention lacked novelty and an inventive step in view of certain prior art. Grenof further asserted that AU’743 does not disclose the invention of claim 1 in a manner which is clear enough and complete enough for the invention to be performed by the skilled addressee, and that claim 1 is not supported by the matter disclosed in the specification (as required by s40(2)(a) and s40(3), respectively, of the Patents Act 1990 (Cth) (the Act)).

Australian Patent No 2014339743 (AU’743)

The technical field of the invention was said to relate to a process and apparatus for manufacture of high solids hydroxide slurries. The specification of AU’743 identified two aspects of the invention, each of which concluded with the phrase:

“…allowing steam to evaporate from the reaction mixture as hydration proceeds, to remove excess heat and control reaction temperature to just below or at the boiling point.”

The concluding words of the two aspects of the invention did not reflect, however, the language of claim 1, which defined control of the maximum reaction temperature “near the boiling point”. It was also noted that AU’743 did not include any consistory statement mirroring the language of claim 1.

According to AU’743 at para [0079], process control was simplified and costs reduced “by using boiling point as a bound to control the process temperature”. It was noted that this and other paragraphs of the AU’743 specification suggested that the boiling point of water was the upper limit of the temperature of the reaction mixture.

In relation to the patent specification of AU’743, Nicholas J opined that the specification:

“…is a confused and muddled document especially when regard is had to the temperature limitation (“near the boiling point”) referred to in claim 1. The broadest description of the invention as it appears in [the specification] … speaks of controlling the reaction temperature ‘to just below or at the boiling point’”.[2]

Common general knowledge (CGK)

It was noted in the decision[3] that boiling can be avoided by the use of less reagent or the addition of more water, and that the reaction mixture can be brought to near boiling point by adjusting the ratio of reagent to water, which would be done through a process of calculation and routine trial and error testing. These are all matters of basic chemistry that would have been well known to the person skilled in the art at the priority date of AU’743. Further, it was common ground between the parties that “to near the boiling point” refers to temperatures near to and below the boiling point of water (i.e., 100ºC at one atmosphere) and “does not encompass temperatures equal to or above the boiling point”.[4]


Video evidence of the Grenof process taken at a joint inspection during the proceeding (at which the experts were present) was shown to the Court at trial. The reaction mixture was shown to reach boiling point, and was giving off steam. Accordingly, the Grenof process was found to be outside the scope of claim 1, and consequently held not to infringe claim 1.


Whilst the 4 prior art documents relied upon by Grenof did not anticipate the claims, the expert evidence established that the CGK at the priority date included methods used to make hydroxide slurries. In particular, the subject of claim 1 was well-known and was actually being performed by persons skilled in the art before the priority date who were seeking to maximise reaction temperatures (in order to reduce batch times) while at the same time avoid boiling (in order to avoid excessive pressure). Ultimately, Nicholas J decided that the invention defined by claim 1 was obvious in light of the CGK, and also obvious in light of 2 of the prior art documents relied on by Grenof when combined with the CGK.

Section 40(2)(a) – “clear enough and complete enough” disclosure

It was noted that AU’743 does not include any working examples of the method defined by claim 1. Despite that, however, because the invention defined by claim 1 reflected what was found to be a well-known method of producing hydroxide slurries that would most likely require the person skilled in the art to undertake routine experimentation[5], a person skilled in the art would be able to perform the invention over the whole of the area covered by claim 1 without undue burden and without the need for invention. As such, AU’743 was found to comply with the requirements of s40(2)(a) of the Act.

Section 40(3) – Support

Although discussion of s40(3) is often focused on the breath of the claim, claims can also lack support because they define an invention that is “materially different” to what is described in the body of the specification, e.g., if a claim includes a feature not disclosed in the specification, or omits a feature that is disclosed. Whether or not the claim will lack support in such circumstances will depend on the proper characterisation of the invention disclosed in the body of the specification and the invention claimed.

The specification of AU’743 disclosed a method of making hydroxide slurry in which the reaction temperature is restricted to “just below or at the boiling point”, and that “[i]mportantly, there is no adverse effect of boiling water on slurry characteristics provided that the water content is managed to account for the loss”[6]. The specification of AU’743 also discussed the use of the boiling point “as a bound to control the process temperature …”.[7] In other words, what was disclosed was a method in which the maximum temperature of the reaction mixture is permitted to reach boiling point. However, Nicholas J decided that this did not support a claim to a method in which the maximum temperature of the reaction mixture is restricted to “near the boiling point”. As the invention as defined by claim 1 was “fundamentally different”[8] from the invention disclosed in the body of the specification, claim 1 was found not to be supported by matter disclosed in the specification.

Summary and significance

In summary, Nicholas J found that claim 1 of AU’743 had not been infringed because the Grenof process for manufacturing its product fell outside the scope of claim 1, as the reaction mixture reaches boiling point and boils.[9] In any event, claim 1 was invalid for lack of inventive step,[10] and non-compliance with s 40(3) of the Act (as the invention as defined by claim 1 was “fundamentally different from the invention disclosed in the body of the specification” and was not supported by matter disclosed in the specification).[11] His Honour therefore ordered that claim 1 of AU’743 be revoked.

This case highlights the importance of the written description, and the complexities in drafting a patent specification. For example, in some places of the patent specification of AU’743, the specification refers to controlling the temperature to just below or at the boiling point, whereas in other places it suggests that the water in the aqueous phase of the reaction mixture is allowed to boil. It is therefore important to be clear on the inventive concept from the outset, to use consistent language in the patent specification and the claims, to take great care in defining the scope of the invention recited by the claims, and to ensure that all amendments are supported. This can be difficult to achieve, as patent specifications are complex to draft. In this regard, see our previous article on the importance of a well-drafted patent specification.

It is important to select an attorney who has technical qualifications and preferably real experience in the field of your invention.