A phosphate-buffered saline (PBS) which, upon rehydration, yields a 0.85% NaCI solution BD Difco™ 100 g. buffered to pH 7.2. BD Difco™ FA Buffer, Dried is used in preparing, e.g.: - Reactive Control Serum (4+) -Unabsorbed - Minimally Reactive Control Serum (1+)