| 摘要 |
PROBLEM TO BE SOLVED: To obtain a pretreatment method in which alcohols as a dispersion medium are not used at all, in which an operation is performed quickly so as to be fed back quickly to a production process and whose measuring accuracy is enhanced by highly dispersing individual salt particles. SOLUTION: Silicon dioxide fine particles in a secondary particle size of 100μm or lower or silicon dioxide fine particles in a secondary particle size of 0.01μm or lower are added to a wet salt or a slurrylike salt at 0.75wt.% or higher with reference to the wet salt or the slurrylike salt, they are mixed and dried, and the surface of the wet salt or the slurrylike salt is covered with the silicon dioxide fine particles. The wet salt or the slurrylike salt is sieved by using a plurality of sieves having a prescribed sieve opening, the wet salt or the slurrylike salt which is left on every sieve and the wet salt or the slurrylike salt which is passed through all the sieves are weighed respectively, and the particle size of the wet salt or the slurrylike salt is measured on the basis of a weighed result.
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