The purpose of this paper is to determine the mass attenuation coefficient (μ/ρ), of a sample. In this work used (C16H32O2) fatty acid, exposed to gamma rays (γ), emitted from various sources 57Co, 133Ba, 22Na, 137Cs, 54Mn, and sCo with energies from 0.122 to 1.330 MeV. It exposes the compound to gamma rays and discloses the radiation force that passes through the sample, the rest of the gamma radiation attenuated. A NaI fluorescence detector (Tl) with an accuracy of 8.2% (at 662 kV) was used for the gamma ray detector beam. An advantage of using (μ/ρ) coefficient data can be obtained effective atomic numbers, atomic cross-section and effective electron densities.