DETERMINATION OF ACCEPTABLE SAMPLE WEIGHT OF MINERAL FERTILIZERS TO KEEP THOSE SAMPLES TO BE REPRESENTATIVE ONES IN TERMS OF PARTICLE SIZE DISTRIBUTION
The article discusses the relationship between the mass of the laboratory sample and the homogeneity of its particle size distribution. The aim of the work is to estimate the limits of the sample mass reduction, at which it remains representative in particle size distribution. A relation was pointed out between the chemical and physical properties and the particle size distribution of fertilizers. The use of this parameter as one of the basic physical properties of industrially produced mineral fertilizers was justified. At the same time, using a smaller sample will reduce the time for analysis in industrial laboratories. An experiment was proposed and implemented to assess the representativeness of sample of fertilizers with different masses. Samples of several brands of industrially produced granulated mineral fertilizers were studied. A sieve analysis of samples was carried out in accordance with accepted standards (for < 1 mm, 1-2 mm, 2-3.15 mm, 3.15-4 mm, 4-5 mm, 5-6.3 mm, > 6.3 mm fractions). A comparison between the obtained results and industry-specific technique for determining the particle size distribution on the woven sieve was given. According to the obtained data, the main statistical characteristics of the analysis were calculated: mathematical expectation (average value), standard deviation and confidence interval. The homogeneity of the average values and variances of the obtained samples for the 50 and 150 g of fertilizers was investigated using Student's and Fisher's tests for a 0.05% level of significance. To confirm the test results, a graphic distribution of sample with different mass and the fraction < 2 mm was built. Conclusion about the allowable mass of a representative sample of granular mineral fertilizers for analyzing the particle size distribution and the associated with physical and chemical properties of fertilizers was made.