Features: 1.Qualitative analysis filter paper is relative to quantitative analysis of filter paper and layer analysis clearly hope that filter paper, paper loose, liquid has a strong absorption function. 2.The training filter paper generally has more residue ash, only for general qualitative analysis. 3.The quick filter paper only waits 3-5 hours relative to the medium-speed filter paper. 3.The filter paper is divided into diffusion ring, sedimentary ring, oil ring. Diffusion ring: The diffusion ring is on the periphery of the sedimentary ring, which is a trace of the outward diffusion of fine particles suspended in the oil. The thinner the particles, the farther they spread.He says the oil additives are able to disperse pollutants. Sedimentary ring: Colors range from light yellow to brownish-red, indicating the degree of oxidation of oil. Package list: 100pcs filter paper