Solubility and Henry's law in code

You will write functions for solubility and for Henry's law. One reads a solubility from a table of measured values. One finds the crystals when a saturated solution cools. One finds how much gas dissolves. The last finds a Henry's law constant from a measurement.

The idea. Between two measured temperatures, the solubility is found by a straight line. Crystals are the fall in solubility, scaled to the mass of water. For a gas, $x = p / K_H$.

Your tasks.

1. Complete solubility_at(temp) with np.interp.
2. Complete crystals(water_g, hot, cold) for a solution that is saturated at hot and cooled to cold.
3. Complete dissolved_mmol(pressure_bar, k_h_kbar) for the millimoles of gas in 1 kg of water.
4. Complete henry_constant(pressure_bar, mmol), which returns the constant in kbar.