Which of the following is the costliest material of construction used in pressure vessel construction?

Tubes of multiple effect evaporator used for concentration of sugar cane juice are made of ________?

In an incompressible fluid, the density is________?

Propellers are________?

Helmholtz free energy A. is defined as________?

Sodium ________ has inverted solubility curve i.e. its solubility increases with the lowering of temperature?