Obvious selection? 

3.1 Obvious and consequently non-inventive selection among a number of known possibilities:

The invention consists merely in choosing from a number of equally likely alternatives.

Example: The invention relates to a known chemical process in which it is known to supply heat electrically to the reaction mixture. There are a number of well-known alternative ways of so supplying the heat, and the invention resides merely in the choice of one alternative.

The invention resides in the choice of particular dimensions, temperature ranges or other parameters from a limited range of possibilities, and it is clear that these parameters could be arrived at by routine trial and error or by the application of normal design procedures.

Example: The invention relates to a process for carrying out a known reaction and is characterised by a specified rate of flow of an inert gas. The prescribed rates are merely those which would necessarily be arrived at by the skilled practitioner.

The invention can be arrived at merely by a simple extrapolation in a straightforward way from the known art.

Example: The invention is characterised by the use of a specified minimum content of a substance X in a preparation Y in order to improve its thermal stability, and this characterising feature can be derived merely by extrapolation on a straight-line graph, obtainable from the known art, relating thermal stability to the content of substance X.

The invention consists merely in selecting particular chemical compounds or compositions (including alloys) from a broad field.

Example: The prior art includes disclosure of a chemical compound characterised by a specified structure including a substituent group designated "R". This substituent "R" is defined so as to embrace entire ranges of broadly-defined radical groups such as all alkyl or aryl radicals either unsubstituted or substituted by halogen and/or hydroxy, although for practical reasons only a very small number of specific examples are given. The invention consists in the selection of a particular radical or particular group of radicals from amongst those referred to as the substituent "R" (the selected radical or group of radicals not being specifically disclosed in the prior-art document since the question would then be one of lack of novelty rather than obviousness). The resulting compounds:

are neither described as having nor shown to possess any advantageous properties not possessed by the prior-art examples; or 
are described as possessing advantageous properties compared with the compounds specifically referred to in the prior art, but these properties are ones which the persons skilled in the art would expect such compounds to possess, so that they are likely to be led to make this selection. 
The invention follows inevitably from developments in the prior art, in such a way that there was no choice between several possibilities (the "one-way street" situation).

Example: From the prior art it is known that when you reach a particular compound in a series of known chemical compounds, expressed in terms of the number of carbon atoms, there is a consistently increasing insecticidal effect as you move up the series. With regard to insecticidal effect, the next member of the series after the member previously known then lies in a "one-way street". If this member of the series, in addition to exhibiting the expected enhanced insecticidal effect, proves also to have the unexpected effect of being selective, i.e. of killing some insects but not others, it nevertheless remains obvious.

3.2 Not obvious and consequently inventive selection among a number of known possibilities:

The invention involves special selection in a process of particular operating conditions (e.g. temperature and pressure) within a known range, such selection producing unexpected effects in the operation of the process or the properties of the resulting product.

Example: In a process where substance A and substance B are transformed at high temperature into substance C, it was known that there is in general a constantly increased yield of substance C as the temperature increases in the range between 50 and 130°C. It is now found that in the temperature range from 63 to 65°C, which previously had not been explored, the yield of substance C was considerably higher than expected.

The invention consists in selecting particular chemical compounds or compositions (including alloys) from a broad field, such compounds or compositions having unexpected advantages.

Example: In the example of a substituted chemical compound given at G‑VII, Annex, 3.1(iv) above, the invention again resides in the selection of the substituent radical "R" from the total field of possibilities defined in the prior disclosure. In this case, however, not only does the selection embrace a particular area of the possible field, and result in compounds that can be shown to possess advantageous properties (see G‑VII, 10 and H‑V, 2.2) but there are no indications which would lead the person skilled in the art to this particular selection rather than any other in order to achieve the advantageous properties.

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