For sulfurization process , controlling the vapor pressure of S is important.How does it vary with temperature and amount of S, how to calculate the vapor pressure of S using ideal gas law..
Jeeva,
The Antoine equation works well under certain circumstances. For sulfur:
log(P) = 6.69535-2285.37/(t+155)
pressure in torr, temperature in Celsius, common logarithm.
From Lange's Handbook of Chemistry, 11th ed.
@ Brian. Thanks but how will you correlate the amount of S with Vapor pressure? means where to include the grams of S??
Jeeva,
Pressure and temperature are intensive variables...they do not depend on the amount of material. If you want to estimate the amount of sulfur in a given volume, then you need to know the volume. Then, knowing the temperature and the vapor pressure from the Antoine equation, you can estimate the amount of sulfur using the ideal gas law, assuming that it is applicable at the temperature and pressure you're using.
Dear Jeeva,
Have you ever left a bottle of water out in the hot sun for a few hours and heard a slight "hissing" noise when you opened it? This is caused by a principle called vapor pressure. In chemistry, vapor pressure is the pressure that is exerted on the walls of a sealed container when a substance in it evaporates (converts to a gas).To find the vapor pressure at a given temperature, use the Clausius-Clapeyron equation:
ln(P1/P2) = (ΔHvap/R)((1/T2) - (1/T1)).
Write the Clausius-Clapeyron equation. The formula used for calculating vapor pressure given a change in the vapor pressure over time is known as the Clausius-Clapeyron equation (named for physicists Rudolf Clausius and Benoît Paul Émile Clapeyron.)[2] This is the generally the formula you'll need to solve the most common sorts of vapor pressure problems you'll find in physics and chemistry classes. The formula looks like this:
ln(P1/P2) = (ΔHvap/R)((1/T2) - (1/T1)). In this formula, the variables refer to:
• ΔHvap: The enthalpy of vaporization of the liquid. This can usually be found in a table at the back of chemistry textbooks.
• R: The real gas content, or 8.314 J/(K × Mol).
• T1: The temperature at which the vapor pressure is known (or the starting temperature.)
• T2: The temperature at which the vapor pressure is to be found (or the final temperature.)
• P1 and P2: The vapor pressures at the temperatures T1 and T2, respectively.
In Case of Sulphur, log(P) = 6.69535-2285.37/(t+155)
Regards,
Prem Baboo
http://www.wikihow.com/Calculate-Vapor-Pressure
Jeeva, sulfur is very non ideal and has many molecular forms. With yellow powder sulfur, you probably have S2 that follows an equation like others have mentioned. When the powder is melted the liquid starts to turn red, which is S6 beginning to be produced and lower the vapor pressure. There might be an equilibrium composition at moderate temperature lasting long enough for your process to run, but at higher temperature the molecules continue to get bigger by polymerization and can become like plastic.
For these reasons some processes run at lower temperatures and with CS2 or other solvent which introduce stability, but also potential hazards of toxic and flammable properties.
For your answer, ideal law does not describe Sulfur, Non ideal laws do but using coefficients that change with composition, time, and temperature.
Sulphur is non-polar in nature so its vapour pressure curve can be calculated accurately using Peng Robinson cubic equation of state or other equations of state which just require its critical properties like critical temperature, critical pressure and accentric factor. However it changes form as you heat it up which cannot be accounted in equation of states. You can use my VLE software, EQ-COMP, showcased at www.eq-comp.com customised for sulphur with suitable critical properties to find vapour pressure curve for sulphur using Peng Robinson cubic equation of state.
www.eq-comp.com
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