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5.23 Section 25(4) requires that the specification shall disclose the invention in a manner which is clear and complete for the invention to be performed by a person skilled in the art. Commonly known as the requirement of sufficiency of disclosure or enablement, Section 25(4) is closely related to Section 25(5)(c), which states that the claim or claims should be supported by the description.
5.24 Section 80(1)(c) states that a patent may be revoked if the specification of the patent does not dislose the invention clearly and completely for it to to be performed by a person skilled in the art. Therefore, non-compliance with Section 25(4) is a ground for revocation of the patent under Section 80(1)(c), and unlike Section 25(5 (c) which can only be applied pre-grant, there is a large amount of case law that relates to Section 80(1)(c) that can be applied to the analysis of Section 2 (4). Because Section 25(4) and 25(5)(c) are closely related, certain aspects of enablement will be considered alongside support in the discussion on the disclosure of the invention below.
5.25 It is not common for an objection to be raised under Section 25(4) pre-grant. The Examiner should give careful consideration when making a sufficiency of disclosure objection, and should reserve such objections for those instances where the invention cannot be readily enabled by narrowing the scope of the monopoly claimed. Usually the invention will also lack support, and Section 25(5)(c) can also be considered as well (this will become apparent when Section 25(5)(c) is discussed below).
5.26 The determination of whether a disclosure is sufficient is highly sensitive to the nature of the invention (Dien Ghin Electronic (S) Pte Ltd v Khek Tai Ting (trading as Soon Heng Digitax)  SGHC 36, Kirin-Amgen Inc v Hoechst Marion Roussel  RPC 9). Thus, the general approach to determine whether a specification complies with the requirements of Section 25(4) is to identify the invention and what it claimed to enable the skilled person to do, and then ask whether the specification enabled him to do it.
5.27 The specification must provide sufficient disclosure across the full scope of the claims (Chiron Corp. v Murex Diagnostics Ltd  RPC 535). At least one embodiment of the invention or at least one method of performing the invention must be described according to Rule 19(5)(e). If the claims themselves provide an enabling disclosure and are supported by the description, then this may provide a sufficient disclosure. In many cases a single example or embodiment will suffice, but where the claims cover a broad field several examples or alternative embodiments or variations extending over the area to be protected by the claims may be necessary. The disclosure of one method of preparation of a product may provide sufficient disclosure for a claim to a single compound (Generics (UK) Limited and others v H Lundbeck A/S  RPC 13).
5.28 However, if the invention is unpredictable in nature then more detail may be required. For example, where the specification claims a synergistic combination and gives little or no guidance on, for example, appropriate concentrations or ratios of the compounds that will provide the synergistic result, it may impose an undue burden on the person skilled in the art to test all possible combinations to determine those that fall within the scope of the claims.
5.29 Claims using functional definitions or that define the invention in terms of a desired result are dealt with in the same manner as any other claim. The specification should provide sufficient information for the skilled person to determine whether or not they have achieved the defined result without undue experimentation and without exercising any inventive ingenuity. For example, a specification defining a device in terms of an improved effect without specifying the degree of improvement and how it could be obtained would be considered insufficient (Birtcher Medical Systems’ Patent BL O/70/96).
5.30 The specification does not need to disclose all the details required to work the invention if these would be known or obvious to the skilled person. In Halliburton Energy Services Inc v Smith International (North Sea) Ltd  RPC 2, Pumfrey J stated that the straightforward test for sufficiency is whether the specification required the addressee to carry out tests or developments that went beyond routine trials. One approach is to ask whether the skilled person would need to discover something new in order to work the invention (Edison and Swan Electric Light Co v Holland, 6 RPC 243 at page 282). It follows that the specification must disclose features that are essential to carry out the invention or provide sufficient detail for the skilled person to work the invention without needing to undertake further invention to do so. These principles were affirmed in Ng Kok Cheng v Chua Say Tiong  SGHC 143.
5.31 Some examples of such considerations are as follows:
Reference to an “autoclave” in the specification without specifying the material of which it is made could be insufficient if it is necessary for the invention to work that the autoclave be made of iron rather than the usual enamel type (Badische Anilin and Soda Fabrik v La Societe etc du Rhone, 15 RPC 359).
In Mayne Pharma v Debiopharm and Sanofi-Synthélabo  EWHC 1123 (Pat), the description related to the preparation of a stable form of oxaliplatin which involved the use of “an effective stabilising amount of a buffering agent selected from oxalic acid or an alkali metal salt thereof”. In this instance, Pumfrey J considered that:
“When one is confronted with a claim which requires ‘an effective stabilising amount’ of a material, it must be possible to design a test which can answer the question ‘Have I used such an amount or not?’. There will always be problems on the edges of claim, but it should in general, be possible to know what the test is. If one cannot identify the test on the basis of the disclosure, then I think that the disclosure is insufficient”.
In this case, the answer to the test was that “you don’t have to add any at all”, and as a consequence the description was found insufficient.
5.32 In Chiron Corporation v Organon Teknika Ltd  FSR 202, claims to a vaccine were found invalid as it took the applicants several years after the filing of the application to develop a vaccine. The description was therefore insufficient as it did not provide sufficient information for a skilled person to repeat the invention without invention.
5.33 A specification claiming a surgical suture made of a particular polymer did not disclose the step of drying the polymer and freeing it from undesired monomer. However, the Court found the patent to be sufficient as these were steps which “the instructed reader desirous of achieving success could be expected, if necessary, to take” (American Cyanamid v Ethicon  RPC 265).
5.34 Errors in the specification will not result in a lack of sufficiency provided they are obvious errors that the skilled person would have recognised and have known how to correct. For example in Ng Kok Cheng v Chua Say Tiong  SGHC 143, the Court dealt with such an error in the following manner:
“It was obviously an error to use the word ‘through’ in the claim in sucha way that it could be argued that ‘through’ applied to both the main body as well as the auxiliary body where the drawings and the prior art, made it quite clear that such could never have been the intention of the inventor. This error could, however, be readily corrected by the skilled performer in the art in the process of making the invention.”