a photometric analyzer and method are disclosed for analyzing particle containing samples . more particularly , a nephelometric apparatus and method are disclosed for analyzing baceteria samples . in the disclosed embodiment , the bacteria count of a bacteria sample is determined by photometrically comparing the sample to another sample having a known particle or bacteria concentration . thus , in accordance with the invention , samples having a known bacteria count may be quickly and easily obtained from a &# 34 ; go &# 34 ; &# 34 ; no - go &# 34 ; test . the bacteria samples obtained according to the invention may be used as standardized bacteria concentrations for conducting kirby - bauer dilution tests .