The invention relates to a method for phenotyping blood andor performing an irregular agglutinin test andor for determination of compatibility of a donor and receiver, using an aqueous solution of ferrofluid, obtained from a mixture of polyoxoanions of Fe and at least one metal M of oxidation state II. In one embodiment, the portable chair has a sling and a chair frame which includes a first pair of bars and a second pair of bars. A technique for capturing the mapping description between data elements of many optionally nested data structures with or without plurality is disclosed.