Question

Thomas slag is:
A.$\text{C}{{\text{a}}_{\text{3}}}{{\left( \text{P}{{\text{O}}_{\text{4}}} \right)}_{\text{2}}}$
B. $\text{CaSi}{{\text{O}}_{3}}$
C.Mixture of A and B
D.$\text{FeSi}{{\text{O}}_{3}}$

Answer 1

Hint:Slag can be defined as the glass-like by-product that is left after the metal is separated from its raw ore and Thomas slag is defined as the finely powdered basic slag obtained in the Thomas-Gilchrist process and it consists of phosphates that is used as fertilizers.

Complete answer:
The Thomas-Gilchrist method is used for the preparation of “tetracalcium phosphate” which can be chemically written as $\text{C}{{\text{a}}_{\text{4}}}{{\left( \text{P}{{\text{O}}_{\text{4}}} \right)}_{\text{2}}}\text{O}$ or $\text{4CaO}\text{. }{{\text{P}}_{\text{2}}}{{\text{O}}_{\text{5}}}$. It is the most basic of all the calcium phosphates and has a Ca/P ratio of 2:1, making it the most phosphorous poor fertilizer. It is found in the mineral “hilgenstock site” which is formed in the industrial phosphate rich slag (Thomas Slag). This slag is used as a fertilizer due to its high solubility in water in comparison to the other apatite minerals.

Hence, the correct answer is option A.
Note:
Thomas slag or the tetracalcium phosphate cannot be prepared in aqueous solutions, any precipitate having the correct Ca/P ratio contains hydroxide anions in apatite phases. Unwanted tetracalcium phosphate can be formed when metal alloy implants are plasma sprayed with hydroxyapatite. Tetracalcium phosphate is stable in water at room temperature upto four weeks but at higher temperature it hydrolysed to form hydroxyapatite and calcium hydroxide. tetracalcium phosphate is used as a component in the formation of hydroxyapatite calcium phosphate cements that have been used to repair bone defects. As tetracalcium phosphate is metastable, the molten reaction mixture has to be quenched rapidly to present the formation of unwanted compounds.