PROBLEMS OF CONCENTRATION DETERMINATION OF INORGANIC ACIDS IN A MIXTURE WHILE RESEARCH ON EXAMINING OBJECTS

Abstract

Inorganic acids are offered for forensic examination of materials, substances and products mainly in the form of individual aqueous mixtures, however, some of the objects are mixtures containing strong and weak acids or two strong acids, which complicates the process of determining the concentration of each component. For that reason creation of an accurate, correct, reproducible, rapid and simple methodology for determining mass fraction, in particular of sulfuric and hydrochloric acids, is also an important step in a reliable forensic assessment of study results.
 To establish applicability of the methods of gravimetric analysis and interpretation of its result for forensic examination, research was carried out on a model three component mixture containing 10 % hydrochloric and 40 % sulfuric acid in an aqueous solution. Determination of sulfuric acid was implemented by means of gravimetric analysis: deposition of SO42-ions by Ba2+ ions with further calculation of acid mass fraction which is 39,05 ± 0,99% that is within the limits of an admissible error (Δхmax ≤ 3σ). The hydrochloric acid was determined by the Volhard method, according to the results of which the mass fraction of acid was 9,56 ± 0,45%, which is within permissible error limits (Δхmax ≤ 3σ).
 Taking into account availability of equipment, simplicity, technological effectiveness, the suggested method for analyzing objects offered for research is an effective method for forensic monitoring of inorganic acids content which are the subject to control measures.