# Calculating the density of liquids LPG liquefied Petroleum gas, by OpenLab CDS Software

Hello, All Agilent Community,

Calculating the density of liquids LPG liquefied Petroleum gas by OpenLab CDS Software ,

When injecting a sample of LPG and when calculating the density of liquefied Petroleum gas,

i found that the result is different from the history of previous samples, and after research and experiments,

I found in the external calculation program that the calculations  SpGrWt equation multiplied by the mole. SpGrWtFract.= Specific_Gravity_H2O*moleFractionNormalized_Dry

Therefore, it gives wrong results.

The equation of SpGrWt was modified and multiplied by the Liquid Volume. This equation before editing.,

SpGrWtFract.= Specific_Gravity_H2O*LiqVolPercent/100

, and we found that the results became correct.

Best Regard's

• I have calculated LPG densities according to ASTM and GPA methods, and find these to be essential to attain agreement between producers and consumers.

Besides Simdist, this is one of the other petrochemical applications where user programming of the HP5880 in HP BASIC was a dream come true, so much easier than manual calculation after collecting the calibrated GC data.

I was also the first independent operator on the Gulf Coast to utilize digital densitometry for cargo work with the original Mettler-Paar DMA10, back when very few of the production plants had yet moved in that direction.  Still have that museum piece in my collection.

Gravity is so important with such large shiploads where the calculated tonnage is based only on volume, and no actual weighing can occur until after the vessel has discharged.   Then each railcar or trailer gets a scale ticket after loading at the terminal.  If the lab gravity is not ideal, the total weights are not going to compare very well.

Since the fourth decimal place in Density can be so critical for things like this, it should be realized the difference between Density (a physical property) and Specific Gravity (a unitless number) is even more significant.

The next step is to run the same samples using a carefully calibrated modern digital densitometer having a proper LPG adapter.  Mettler and Anton Paar have been separated for decades now but each can get something like this for you.

Not everyone may be very satisfied when comparing the real thing to calculated gravity values.  You may not like what you see.

Don't forget to allow for different jurisdictions where the density of air and its resultant buoyancy is not handled identically.

Buoyancy is essential for ships and blimps, the bigger they are the more it means.

• Dear Mike,

I thank you very much for this valuable information, and I wish you continued success. I also know the importance of density measurements for producers and consumers, so we do the measurement based on the ASTM, GPA, and also using the calibrated modern digital densitometer having a proper LPG adapter. Mettler Toledo apparatus. I appreciate your interest and thank you very much,

with my wishes for permanent success.

Best Regards,