Introduction:
Refractories are materials that are resistant to high temperatures and are used in various applications such as lining furnaces, kilns, and reactors. The chemical composition of refractories determines their properties and behavior at elevated temperatures. One important component of refractories is silicon, and its content can have an impact on the characteristics of the refractory material.

Explanation:

1. Acidic Refractories:
- Acidic refractories are composed of acidic materials such as silica (SiO2) and alumina (Al2O3).
- These refractories are highly resistant to acidic environments and are commonly used in industries where acidic conditions are prevalent.
- The high content of silicon in refractories does not make them acidic, as the presence of other acidic materials such as silica is necessary for a refractory to be classified as acidic.

2. Basic Refractories:
- Basic refractories are composed of basic materials such as magnesia (MgO), dolomite (MgO-CaO), and chrome-magnesia (Cr2O3-MgO).
- These refractories are highly resistant to basic environments and are commonly used in industries where basic conditions are prevalent.
- The high content of silicon in refractories does not make them basic, as the presence of basic materials such as magnesia is necessary for a refractory to be classified as basic.

3. Neutral Refractories:
- Neutral refractories have a balanced composition and are resistant to both acidic and basic environments.
- The high content of silicon in refractories indicates a balanced composition and makes them neutral.
- Silicon is known for its high melting point and resistance to thermal shock, which makes it an ideal component for neutral refractories.
- Neutral refractories are commonly used in industries where both acidic and basic conditions may be encountered.

4. Brittle Refractories:
- The brittleness of refractories refers to their tendency to break or crack under stress.
- The high content of silicon in refractories does not necessarily make them brittle.
- The brittleness of refractories depends on various factors such as their composition, microstructure, and processing conditions.
- While high silicon content can contribute to the brittleness of some refractories, it is not the sole determining factor.

Conclusion:
In conclusion, if a refractory contains a high content of silicon, it indicates a neutral refractory. The high silicon content in refractories contributes to their balanced composition and resistance to both acidic and basic environments. However, it is important to note that the brittleness of refractories is not solely determined by their silicon content and depends on various other factors.