Abstract: Negative ion mass spectra were taken of various types of samples--metals, alloys, semiconductors, insulators and solutions. Regularities of line strengthwere summarized on this basis. Such favorable specialities of negative ion massspectra as simplicity, absent of multicharged ions, high resolution and high re-lative ion yield for nonmetal elements have been used with advantage in chemi-sal analysis. Difficulties encountered in the preparation of electrodes for solu-tion samples were overcome by using borax as matrix. Detection limits of fluo-rine, chlorine, bromine and iodine in borax matrix were determined to 2×10~(-5) andcound to be dependent on the chemical form of the species,