What is the substance known as 'blanc fixe' used in paints?

The tendency of forming chloride hydrates of alkaline earth metals is in the order of

Amongst the following hydroxides,the one which has the highest value of $K_{sp}$ at ordinary temperature is

Fill in the blanks:
$(1)$ Calcium and beryllium have flame colors of ...... and ....... respectively.
$(2)$ Quantitative analysis of calcium is carried out by ........
$(3)$ Beryllium powder on combustion burns brightly in air and gives ...... and .......
$(4)$ Beryllium hydroxide on dissolving in alkali gives .......

Property of the alkaline earth metals that increases with their atomic number is

Lime reacts exothermally with water to give '$A$' which has low solubility in water. Aqueous solution of '$A$' is often used for the test of $CO_{2}$,a test in which insoluble $B$ is formed. If $B$ is further reacted with $CO_{2}$ then a soluble compound is formed. '$A$' is