1, Determination of calcium carbonate content
The original industry standard used acid-base back titration to determine the main content, expressed as calcium carbonate. Actually, the carbonate in the sample is measured and calculated as calcium carbonate, indicating the main content, which does not accurately reflect the content of calcium carbonate in the sample. GB/T 19281-2003 “Ultrafine Calcium Carbonate” stipulates the method of complexometric titration for the determination of calcium carbonate content. In order to truly reflect the actual content of calcium carbonate in the product, this revision adopts GB/T 19281-2003. The method specified in Ultrafine CaCO3 uses the complexometric titration method to determine the content of calcium carbonate and the triethanolamine as a masking agent. When the pH is higher than 12, the calcium carboxylate sodium salt is used as an indicator, and the 0.02mol/L EDTA standard is used. Titrate the solution titration. This method is a classical method for measuring calcium content. By adding triethanolamine to mask the interference of metal ions such as iron and aluminum, and then adjusting the pH value of more than 12 to eliminate Mg interference, the measurement result is accurate and the operation is simple, and it has been proved by practice.
2, the measurement of fineness
The sample was dispersed by a dispersant and measured by a centrifugal sedimentation particle size analyzer or a laser particle size analyzer. At present, the measurement of particle size has a different condition with different instruments, that is, the problem of poor reproducibility. However, for the same instrument, the same dispersant and dispersion time can be used to distinguish the difference in particle size for different samples. It is considered that the heavy calcium carbonate is classified by a cyclone classifier during processing. This test method is applicable to the particle size range of enterprise control products, and at the same time considers the inconsistency of the current enterprise instruments. Therefore, the comparison results of the same product with the two instruments in this standard are as follows:

As can be seen from the table above, there is a significant difference in the methods used to determine the two instruments. Therefore, the two methods cannot be juxtaposed. At present, from the analysis of the samples and data sent, as well as the current occupancy of the instrument, the current standard recommends using a laser particle size analyzer to determine its fineness.
3, the determination of whiteness
The original industry standard stipulates that the whiteness meter is used for the determination. The measured blue lightness is expressed in terms of Wr. The whiteness measured in GB/T 19281-2003 Calcium Carbonate Analysis Method refers to the whiteness measured by the tristimulus value method stipulated in GB/T 5950-1996 "Method for Measuring Whiteness of Building Materials and Non-metallic Mineral Products". To Wj. As the industry is accustomed to using blue light, the original standard uses blue light, this revision uses blue light.
4. Determination of specific surface area
According to the method specified in GB/T 19587-2004, the relative pressure P/P0 of ethanol is adsorbed between (0.05-0.35) using a mixed solution of ethanol and diethylene glycol. After adsorption, the BET equation is applied to obtain the surface area thereof. .
5. Determination of oil absorption value
The original industry standard stipulates that 5 g of the sample is to be taken, and the DOP is added. The DOP is blended with a knife and the amount of DOP used is weighed to calculate the oil absorption value. The current method commonly used by manufacturing companies is to express the oil absorption value by the volume of DOP consumed per 100 g of sample. The unit of the oil absorption value is mL/100 g.
6. Volatile content at 105°C
The original industry standards and GB/T 19281-2003 "Calcium carbonate analysis method" provides the same analytical method: Weigh 2g samples, placed at (105 ± 5) °C dry to constant weight. This revision refers to the measurement method specified in GB/T 19281-2003.
7. Determination of Insoluble Hydrochloric Acid Content
The original industry standard and GB/T 19281-2003 "CaCO3 Analytical Method" stipulate that the sample is dissolved with hydrochloric acid and the insoluble matter is filtered, washed, dried and weighed. This revision refers to the measurement method specified in GB/T 19281-2003.
8. Determination of dark foreign bodies
Weigh 1g sample, placed on two clean 100mm x 100mm slides, gently rolling to the sample tile, with 10 times the number of magnifiers to take samples deep brown-yellow particles. There shall be no more than 5 dark foreign objects per gram of sample.
9. Determination of lead
The content of lead in the sample was determined by atomic absorption spectrophotometry. The sample was dissolved and acidified, and the lead content was determined by atomic absorption spectrophotometry at a wavelength of 283.3 nm.
10. Determination of hexavalent chromium
Determination of hexavalent chromium content, using spectrophotometry. The solution was made acidic, so that hexavalent chromium ions and diphenylcarbazide formed a rose-red chromium complex, and colorimetric determination was carried out to determine the chromium content.
11. Determination of mercury
Measurements were made using a visible spectrophotometer. That is, after the sample is digested, the mercury ion forms an orange-red complex with dithizone in an acidic solution and is dissolved in chloroform, which is compared with the standard series.
12. Determination of arsenic
The repairs were performed using the arsenic spot method. That is, in the acidic medium, in the presence of potassium iodide and stannous chloride, the high-valent arsenic in the sample solution is reduced to trivalent arsenic, and the new ecological hydrogen generated by trivalent arsenic and zinc particles and acid generates arsine gas, which passes through acetic acid. Lead cotton removes interference from hydrogen sulfide, and then generates a yellow to orange stain with a mercury bromide test strip. This is compared to a standard arsenic spot to make a limited test.
13. Determination of cadmium
The atomic absorption spectrophotometric method is used to determine the content of cadmium in the sample. After the sample is dissolved in nitric acid solution, the atomic absorption spectrophotometer is used to determine the specific absorption wavelength of cadmium by the atomic vapor generated from the standard solution and the test solution. Absorbance, do the work curve, check the quality of the sample solution cadmium from the working curve to determine the content of cadmium in the sample.
14, packaging comparison
The packaging of various companies basically implements the original industry standards. This revision still maintains the original industry packaging method.