THE EFFECT OF THE SAMPLE PREPARATION PROCESS ON THE RESULTS OF DETERMINING THE PHASE AND CHEMICAL COMPOSITION OF MINERAL FERTILIZERS AND FEED PHOSPHATES

The paper considers the features of sample preparation in determining the quality parameters of mineral fertilizers and feed phosphates. When determining the mass fraction of water in monocalcium phosphate during drying of the sample at a temperature of (100-105) °C, in addition to hygroscopic moisture, carbon dioxide is removed, which is formed because of the neutralization reaction of free phosphoric acid with unreacted chalk. This is reflected in the amount of mass loss of the sample, and, accordingly, in the results of measuring the mass fraction of water in monocalcium phosphate. The results of determining the phase composition of monocalcium phosphate samples when grinding to 160 and 40 µm are presented. It was found that when grinding to 40 µm an increase in the content of calcium dihydroorthophosphate monohydrate in the monocalcium phosphate sample occurs. This indicates an active water sorption process from the surrounding air by the monocalcium phosphate sample. The continuation of the neutralization reaction between residual phosphoric acid with chalk during drying of monocalcium phosphate samples at 80 °C during sample preparation to determine the mass fraction of free phosphoric acid is revealed. This leads to a distortion of the results obtained. The results of determining the phase composition of model mixtures of reactive salts are presented. An increase in the degree of conversion reactions between components in model mixtures of salts is shown, which occurs because of grinding the sample during its preparation for determining the phase composition by the XRD method. With this in mind, the influence of sample preparation on the results of determining the phase composition of complex mineral fertilizers should be taken into account. For citation: Maksimova A.A., Romanova S.P., Sokolov V.V., Sokolova A.S., Kochetova I.M. The effect of the sample preparation process on the results of determining the phase and chemical composition of mineral fertilizers and feed phosphates. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2025. V. 68. N 5. P. 20-27. DOI: 10.6060/ivkkt.20256805.4f.