The phrase "a purpose of which" is correct and usable in written English.
It can be used when referring to a specific purpose related to a previously mentioned subject or object.
Example: "The project has a clear goal, a purpose of which is to improve community engagement."
Alternatives: "a goal of which" or "an aim of which".
These women awaken in Lilith a "true darkness and true womanness," revealing to her a purpose of which she has been unaware.
What counted more was the ebbing of the idea that America was at war for a purpose of which it could feel proud.
The suspect was acting in his or her capacity as a person involved in the management or as an employee (whether for payment or not) of an organization or group, a purpose of which is to provide a physical environment (whether for payment or not) in which to allow another to commit suicide.
In principle, a sensor is a device, purpose of which is to sense (i.e., to detect) some characteristics of its environs.
She said the material was "highly inflammatory when our country is currently engaged in a war against terrorism in Afghanistan, a prime purpose of which is to arrest Osama bin Laden".
For inhabitants of cities to live an enriched life in every means, they require more than just the infrastructure and the trappings of material wealth: They require an attachment to a place, a sense of belonging and a sense of purpose, of which, a sound cultural development can help generate.
This was the second phase of a study, the purpose of which its purpose was to determine the childbirth expectations of a cohort of Western Australian women and ascertain factors that influenced these expectations.
Immunologically, however, there is always a response, the purpose of which is defense.
In a dissenting report, justice Stephen Gageler said detention without charge was punitive, and the paperless arrest laws made the courts "support players in a scheme the purpose of which is to facilitate punitive executive detention".
Although most modern soil classification systems are based on soil properties, the soil map remains a model, the purpose of which is to predict the spatial distributions of those properties.
Israel responded to the rockets by declaring a blockade, the purpose of which was to assure that no rockets, or other material that could be used for making war against Israeli civilians, was permitted into Gaza.
