Question

What is tincal? Give its chemical formula.

Answer 1

Hint: Borax is naturally found as a mineral which is known as tincal. It is also known as sodium tetraborate decahydrate and it is a colorless crystalline substance used in laundry and cleaning products.

Complete answer:
Minerals are naturally occurring solid compounds which have a definite chemical composition and crystalline structure. They are formed naturally on Earth. Similarly, tincal is a naturally occurring mineral form of an inorganic compound that is called Borax.
Borax is a crystalline colorless substance soluble in water and it is commonly found as tincal which has the chemical formula - $\text{N}{{\text{a}}_{\text{2}}}{{\text{B}}_{\text{4}}}{{\text{O}}_{\text{7}}}\text{.10}{{\text{H}}_{\text{2}}}\text{O}$. However, borax can be found with different water of crystallization, the most common form of borax is sodium tetraborate decahydrate compound. The structure of this compound consists of a tetranuclear unit as shown below and thus the actual formula of borax is written as - \[\text{N}{{\text{a}}_{2}}\left[ {{\text{B}}_{4}}{{\text{O}}_{5}}{{\left( \text{OH} \right)}_{4}} \right].8{{\text{H}}_{\text{2}}}\text{O}\]

Tincal is obtained from dried up lakes and it contains 50%-55% borax. The pure borax is obtained from naturally occurring tincal by the recrystallization process. In this process, the first tincal is boiled in water to get a concentrated solution from which then pure borax crystals can be filtered and dried out.

Note:
Borax can also be obtained from other compounds such as boracite and colemanite. There are many uses of borax:
(1) – It is used as a water and fabric softener.
(2) – It is used as a flux in welding and soldering.
(3) – It is also used in disinfectants.
(4) – Also used as an additive in fertilizers.