Why doesn't sulfuric acid corrode glass?

For some people, there is often such a question: sulfuric acid is very acidic and is one of the three strongest acids in the world. Why can't sulfuric acid corrode glass? In fact, this is mainly due to the problem of glass composition. We know that the main component of glass is silicon dioxide, and silicon can only react with one kind of acid, that is, hydrofluoric acid. Therefore, sulfuric acid does not have the effect of corroding glass.

Why does sulfuric acid not corrode glass? The main component of glass is quartz, namely silicon dioxide (SiO2), which is very hard. In addition, it has the property of transparency. It is widely used as glass windows, optical instrument glass, and various chemical and daily containers. In various chemical experiments, people always hope to directly see the chemical reactions inside the container. Only glass can do this because it is transparent and can resist corrosion from various chemicals. Most metals will undergo chemical reactions when they come into contact with acids. Even gold, the relatively stable "king of metals", is tamed and dissolved when it comes into contact with "aqua regia" which is a mixture of nitric acid and hydrochloric acid. Only glass is not afraid of corrosion by hydrochloric acid, sulfuric acid, nitric acid and even aqua regia. Only caustic soda can slightly corrode the surface layer of glass. Therefore, glass became the darling of chemists, and even became the nickname of chemists as "glass test tube experts".

Although glass is fragile, it is very hard and can withstand much greater pressure than pig iron. Someone has done an experiment like this: adding heavy objects to blocks of cast iron and glass of the same size. When the weight reached one hundred kilograms, the pig iron was crushed, but the glass remained intact. The glass blocks only broke when the pressure reached over 180 kilograms. Faced with such a hard temper, if we use knives, scissors, awls and saws made of ordinary steel and cannot scratch it at all, only knives made of high-grade alloy steel and diamond grinding wheels can scratch it.

Physical properties of sulfuric acid

Pure sulfuric acid is generally a colorless oily liquid with a density of 1.84 g/cm3 and a boiling point of 337°C. It is miscible with water in any proportion and releases a large amount of heat, causing the water to boil. When heated to 290°C, sulfur trioxide begins to be released, eventually becoming a 98.54% aqueous solution, boiling at 317°C to form an azeotropic mixture. The boiling point and viscosity of sulfuric acid are relatively high because of the strong hydrogen bonds within its molecules. Due to its high dielectric constant, sulfuric acid is a good solvent for electrolytes, but a less ideal solvent for non-electrolytes. The melting point of sulfuric acid is 10.371°C. Adding water or sulfur trioxide will lower the freezing point.

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