If we study the dependence of the boiling point of the composition of the solution, the chart structure-boiling point when p=const.

That of two fluids, which has a large vapor pressure, boils at a lower temperature. Get the chart, which is a mirror image of the previous in the pressure-composition.

p t=const t p=const

tIn

liquid vapor

W+p W+p

t_And

vapor liquid

AND IN AND IN

a b

Rice. 10.4. Chart: and) the composition-vapor pressure and b) the composition-temperature boiling of binary mixtures

Consider in more detail the graph structure-boiling point (rice. 10.5).

A mixture of two liquids boils at a certain temperature range, as boil as its composition is changing.

t p=const

couples F

W+p C

liquid •M

A m B

composition

Rice. 10.5. Chart composition is the boiling point of a dual liquid system without extremum

The chart (rice. 10.5) bottom line (curve of the liquid) depicts the initial boiling point of solutions of different compositions, and the top line (curve pair) – temperature end of the boil. Point and - boiling points of pure components A and b.

Isothermal corresponding points on these curves C and , F and show the composition of liquid and vapor phases, in equilibrium with each other.

Evaporation of the solution M m composition begins at a temperature of (point C in figure. 10.5). As the evaporation of conjugated compositions of the solution and the vapour are changed along the curves of liquid and vapor; at the same time decreases the amount of fluid, and the amount of vapor increases (shoulders of the levers, the liquid phases, shown in solid lines, and steam phases – dotted). At a temperature of evaporation and ends at a higher temperature, there is only vapor.