through the FDA ISO 9001 use for fertilizer : NAME OF INDEXINDEXRESULTAPPEARANCEWhite CrystalCompliesMain Content≥%9999.2Mg≥%9.59.56S≥%12.512.64PH value4.5-6.55.0Chlorid(Cl)≤ppm150135Iron(Fe) ≤ppm 1513Heavy metal(Pb) ≤ppm86Arsenide(As) ≤ppm21Water insoluble≤ppm105Particle size (mm)0.1-10.1-1ConclusionCompliesUse :--Mainly used in fertilizer, tanning, pringting and dyeing,activator,papermaking, ...