Titanium dioxide: chemical name titanium dioxide, which is an acidic amphoteric oxide with excellent thermal stability. It hardly reacts with other elements and compounds at room temperature and has no effect on oxygen, ammonia, nitrogen, hydrogen sulfide, carbon dioxide and sulfur dioxide. Insoluble in water, oleic acid, inorganic acid and alkali, soluble in hydrofluoric acid. Titanium dioxide is not only used as a colorant in rubber industry, but also has the functions of reinforcement, aging resistance and filling. Titanium dioxide itself is non-toxic, and adding titanium dioxide into purple sand mud mainly plays the role of filling and coloring (yellowing). Therefore, titanium dioxide is mainly used in yellow mud such as gold segment and yellow sesame segment, and the clay pot without adding is darker in color.

Manganese oxide: The chemical name is manganese oxide, black amorphous powder, or black diamond crystal. The melting point of manganese oxide is 1650 degrees Celsius. The stability of manganese dioxide in ceramic industry is also quite high. After firing at high temperature, it becomes manganese silicate, and its properties are relatively stable. Insoluble in water, nitric acid, cold sulfuric acid and weak acid and alkali, but soluble in concentrated hydrochloric acid will produce chlorine. In order to make purple clay darker, adding a small amount of manganese dioxide is basically harmless to human body. It is common to add purple mud to make clay pots such as black pier heads. Generally speaking, once the design temperature of fired clay samples is not high, the possibility of using this chemical material is not high.

Iron red powder: This may be a chemical that all friends who play with clay pots are curious about. Chemical name iron oxide, red powder. Iron red powder is a kind of basic ceramic additive, which is widely used in ceramic construction (such as roof tiles), rubber, plastics, coatings (generally used as anti-rust treatment for steel components) and other industries. Iron red powder is composed of pure iron oxide, which is light-resistant, high-temperature-resistant, atmospheric-resistant, dirty-gas-resistant and alkali-resistant, with stable performance and insoluble in water and weak acids and alkalis. Soluble only in silicate at high temperature, and gradually dissolved when heated in concentrated acid. 20 10 April, after Guangdong fake teapot was exposed, Liu Jiaoshou, the State Key Laboratory of Materials Chemical Engineering, told 3 15TS that iron red powder was basically harmless to human body. Generally speaking, after adding iron red powder, it is all red mud, sold as cinnabar, with deep red hair color and deep red color. Generally, iron red powder can only be added if it is ground into extremely fine purple sand soil, and more than 95% of "cinnabar" pots can be added ~

Cobalt oxide: chemical name cobalt monoxide, usually gray powder, sometimes green-brown crystal, melting point 1935 degrees Celsius. Commonly used as colorants for glass, enamel, ceramics, sky blue, cobalt blue, cobalt green and other colors, it is easy to be reduced to metallic cobalt by carbon monoxide. At high temperature, silica, alumina or zinc oxide can easily react to generate multicolor compounds, which are dissolved in water, acid and sodium hydroxide aqueous solution.

Chromium oxide green: also known as chromium trioxide and chromium oxide, it is hexagonal system, green powder, magnetic, strong hiding power, high temperature resistance, sun resistance, insoluble in water and acid, relatively stable in the atmosphere, and has no influence on ordinary concentration of acid, alkali and sulfur dioxide gas. It has excellent pigment quality and fastness, and its Mohs hardness is 8.5-9, which is close to corundum and second only to diamond. Chromium oxide green is stable when exposed to heat, with a melting point of 2266 degrees Celsius and a boiling point of 4000 degrees Celsius. Slightly soluble in concentrated sodium hydroxide solution, hot sodium bromate solution, hot concentrated perchloric acid solution or boiling mixed acid of sulfur and phosphorus, it is a high-quality refractory. Widely used in metallurgy, pigments, grinding and polishing, refractories and newly developed melt-blown coatings. The addition of chromium oxide green in purple sand soil mainly plays a coloring role, and its hue is green in the middle, which is different from the blue in the middle of cobalt oxide. This coloring is generally harmless to the human body. It is rarely used mainly because the raw materials are expensive and the unique color of the teapot is lost, not because it is toxic and harmful. However, some mud refiners who don't know chemical knowledge may be in danger of adding too much when refining mud.

Barium carbonate: At present, almost all teapots on the market have added barium carbonate. I believe that pot friends who have been playing pot for some years have their own understanding channels for barium carbonate. Let me say it briefly. Barium carbonate is a common inorganic salt. Industrial products are white powder, which is toxic in itself. Metal barium is generally non-toxic, while soluble barium salt is highly toxic to human body, with a toxic dose of 0.2-0.5g and a lethal dose of 0.8-30g. Barium carbonate is almost insoluble in water and alcohol, and its solubility in water is only 0.002g g. Adding proper amount of barium carbonate to purple mud is mainly to improve stability, flux, neutralize acid and alkali, and generate barium sulfate after firing. Barium sulfate is insoluble in neither water nor gastric acid, so it cannot be absorbed by human body, so it will not cause harm to human body. The function of barium carbonate is to inhibit the appearance of flower mud in the fired finished product.