Measure Density with a Pycnometer
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- เผยแพร่เมื่อ 15 ก.ย. 2024
- This video shows how to use a pycnometer for density measurement of liquids:
- How to measure (filling the pycnometer with the sample, bringing it to the set temperature in a water bath, weighing and calculating the density from the weighing results).
- How to clean the pycnometer to be ready for the next measurement.
- How to determine the exact volume of a pycnometer by weighing air and water.
Learn more about the 3 methods for density measurement: hydrometers, pycnometers and digital hydrometers
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Learn more about digital density measurement with expert tips, download our free guide here:
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Checkout our digital density meters here:
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00:03 Measure the density of a sample with a pycnometer
01:35 How to clean a pycnometer
02:38 Determine the exact volume of a pycnometer
04:32 Digital density meters
May I know the model of the water bath used in the demo?Also, when the capillary is visually seen not to be full, the instruction says that need to fill usimg capillary but in the video, the capillary is further inserted,can explain that part?
Great thanks now I understand the concept!
You are welcome!
In the formulas, "Dair" is the density of air, while "Mair" is the mass of the pycnometer filled with air (not the mass of the air in the pycnometer; perhaps a better subscript could be used?).
Correct, the Dair is the density of air. The "Mair" is the mass of the pycnometer filled with air (empty).
Practically in the
experiment of calculating the density of the soil, why is the picnometer placed in the heating basin and left for 10 minutes at a temperature of 30c??
The density of a sample is temperature dependent. Pycnometers are calibrated for a certain temperature, e.g. 30 °C, so measurements are only valid at that temperature. Sample must be equilibrated to the calibration temperature. Find more information under www.mt.com/gb/en/home/library/guides/lab-analytical-instruments/density-measurement-guide-3-ways.html
sorry for asking, is it okay to handle the pycno only by bare hand? even not using glove or covering-tissue instead?
thanks for helping me, cheers.
Generally, we always recommend to wear gloves, goggles and lab coats. In this video no gloves are used as this is a video for presentation only.
Can you please tell that why you use the same unit ''cm3'' for density and volume?
The unit we use for density is g/cm^3, the one for volume is cm^3. At 1:26, the g is missing. Thank You for pointing this out.
Also instead of leaving my sample in water bath, can I leave my sample inside oven and adjust the temperature accordingly? Will that work? Say, by adjusting the temp to 40 Degrees etc. Will that work?
In all standards/literature, temperature control is carried out in a water bath. It can be assumed that the heat exchange takes place faster in a water bath than in the air.
We would recommend adhering to the specifications in the standards/literature.
If an oven is used, it must be possible to control the temperature very precisely and we would suggest making comparative measurements.
Why do we subbract Dair from Dwater? Is it because Mwater - Mair is a little less than the mass of water as we subtracted the mass of air too? So we must adjust our density to include air too
Electrodes should always be stored in aqueous and ion-rich solutions. This ensures that the pH-sensitive gel layer which forms on the pH glass membrane remains hydrated and ion rich. This is necessary for the pH membrane to react in a reliable way with respect to the pH value of a sample. Short term storage: In between measurements or when the electrode is not being used for brief periods of time, it is best to keep the electrode in a holder containing its inner electrolyte solution (e.g. 3 mol/L KCl), or in a pH 4 or pH 7 buffer. Ensure that the level of solution in the beaker is below that of the filling solution in the electrode. For long term storage: Keep the electrode wetting cap filled with the inner electrolyte solution, pH buffer 4 or 0.1 mol/L HCl. Make sure that the filling port for reference and combination electrodes is closed to avoid loss of the electrolyte solution through evaporation, which can cause the formation of crystals within the electrode and junction. Never store the electrode dry or in distilled water as this will affect the pH-sensitive glass membrane and thus shorten the lifetime of the electrode.
Hi, if i need to check the density of Liquid chocolate at 40 Degrees, do i need to adjust the volume accordingly as well, all to be checked in 40 Degrees?
Yes, in case the sample needs to be measured at 40 °C, the pycnometer has to be calibrated for that temperature. Pycnometers are calibrated for a certain temperature, so measurements are only valid at that temperature!
With METTLER TOLEDO’s digital density meters, the sample can be measured at ambient temperature. If a result is needed at a certain temperature, the digital density meter can apply a correction factor to the measured result to compensate the result to a defined temperature. The digital benchtop instruments in addition feature built-in temperature control. The integrated Peltier temperature control quickly heats up or cools down the measurement cell, allowing you to perform your analyses directly at the desired temperature.
For more information please visit: www.mt.com/global/en/home/products/Laboratory_Analytics_Browse/density-meter.html
I need a video on how to do analysis palm stearin oil density
METTLER TOLEDO does not have a video on how to measure the density of palm stearin oil with a pycnometer. In general, palm stearin oil can be handled like any other edible oil and fat.
The most common standards for edible oils and fats, e.g. AOAC 921.08, define refractive index measurements at a certain temperature (at 20 °C/40 °C). METTLER TOLEDO's digital benchtop instruments have an integrated temperature control that allows you to achieve more accurate results. The integrated Peltier temperature control quickly heats up or cools down the measuring cell so that you can perform your analyses at the desired temperature.
For more information please visit: www.mt.com/global/en/home/library/applications/lab-analytical-instruments/refractive-index-of-oils-and-fats-aoac-92108.html
Why dry the device with air and not in the microwave??
The flask volume might slightly change by excessive heating. It is therefore recommended to dry the exterior of the pycnometer using a paper towel or cloth and to let it then dry at air. Find more information under www.mt.com/gb/en/home/library/guides/lab-analytical-instruments/density-measurement-guide-3-ways.html
Hi, what agent do you use to clean the pycnometer? Thanks!
In this video Acetone was used.
But before the beginning of rinsing, remove all sample from the pycnometer. For each kind of sample, 2 appropriate rinsing solvents have to be defined.
Purpose of the 1st rinse: Must be able to completely and quickly dissolve all the sample, so that no contamination is left in the cell. This solvent is often not very volatil
Purpose of the 2nd rinse: Must completely dissolve the 1st solvent above, and it must evaporate quickly without
leaving any residue to enable quick drying afterwards. Please make sure that this solvent is free of water, otherwise it does not evaporate quickly enough. The use of acetone is preferred. If acetone is not allowed, use ethanol
(must be puriss >99.9%, NOT 96% and NOT denatured)
This is basically the same steps used to clean the measuring cell of our density meters. If you want to learn more about density measurement, check out this free guide: www.mt.com/global/en/home/library/tips-and-tricks/lab-analytical-instruments/density-measurement-guide.html
How did you obtain the density of air?
The density of air depends on factors such as air temperature, humidity and air pressure. At sea level, the density of dry air at 20 °C and 1013.25 hPa is approximately 0.001205 g/cm3.
The value of 0.001152 g/cm3 shown in this video corresponds to the test conditions when carrying out this experiment.
Super
Thanks