Measuring Density with Pycnometers, Hydrometers, and Graduated Cylinders

I am a retired analytical chemist. One mistake I noted was the lack of gloves when handling analytical glassware. Finger prints have mass and will change resuls in the second to the third decimal place depending on cleanliness of hands. Also, non-conducting liquids will suffer from static charges so an anti-static device is recommended. Otherwise your chemistry is excellent as ever Dr. Nurdrage!

As a non-chemist, I sometimes find these videos more interesting than your others. It feels like I'm legit learning something rather than watching a magic trick.

When you started mentioning the "U-Tube density meter" I started thinking that youtube had some means of measuring the density of human minds.

The flask grinding part was something I had heard about but I hadn't seen anyone actually do it - super useful

Non physical things such as minds, which can be exceptionally dense. Solid gold.

The mass of YouTube and the density are off the charts

I am not any sort of chemist but I still find this kind of stuff super interesting. It's about human ingenuity and how people figured out interesting ways to solve problems and that is always interesting at least to me. I will probably never need to know how to do any of this but I like knowing it anyway.

I’m definitely a fan of flashy synthetic chemistry stuff, but I really appreciate the analytical deep dives. I always learn something new and analytical chemistry is in the “how the sausage gets made” territory of chemistry. Dreadfully unsexy but damned useful. Thank you for years of contributions to the science!

As one who also enjoys maker channels, I couldn’t help but think when seeing the gas pycnometer and U tube device, “those are things that a lot of folks could make themselves if push came to shove.”

That's basically what is the topic of a practical exam I need to take in a few weeks to become a chemical lab assistant. Love my job but the pycnometer makes me wanna end myself sometimes.

This is one of my favorite videos that you ever made and i have been watching since the beginning

Summary Basic Density Measurement * (1:20) Graduated cylinders are a simple but not very accurate way to measure liquid density. * Weigh the empty cylinder, add liquid, weigh again, and divide the mass difference by the volume reading. * Errors can arise from temperature differences and meniscus readings. Specialized Tools and Techniques * (2:47) Hydrometers are inexpensive floaters that directly indicate density on a calibrated scale. * Easy to use, just float in the liquid and read the scale. * Great for quick checks, like monitoring home brewing or electrolyte concentration. * Limited measurement range (often 1-1.2 g/mL), not suitable for all liquids. * (5:04) Pycnometers are precise volumetric flasks with a capillary hole in the stopper to ensure a reproducible volume. * Calibrate by weighing empty, then filled with a liquid of known density (usually water). * Fill with the unknown liquid, weigh, and calculate density using the calibrated volume. * Much more accurate than graduated cylinders and hydrometers. * Affordable for amateurs, with professional models offering even greater precision. * (9:14) Grinding Pycnometer Stoppers * Cheap pycnometers may have wobbly stoppers that can be improved by grinding. * Use valve grinding compound and a hand drill (with caution!) for a tighter fit. * Not strictly necessary for amateur use, but improves accuracy for perfectionists. Measuring Solid Density * (14:34) Archimedes' Principle: A submerged object experiences an upward force equal to the weight of the displaced liquid. * Weigh the solid, then submerge it in a liquid of known density (water is common). * Measure the weight difference to calculate the volume of liquid displaced, which equals the solid's volume. * Divide the solid's mass by its volume to determine density. * (17:17) Powder Density with a Pycnometer: * Calibrate the pycnometer as usual. * Choose a solvent that the powder doesn't dissolve (or has very low solubility) in. * Create a saturated solution of the powder in the solvent. * Fill the pycnometer with the powder, then add the saturated solvent to fill the gaps. * Carefully remove air bubbles. * Measure the mass of the powder + solvent, subtract the known mass of the powder, and use the solvent's density to calculate its volume. * Subtract the solvent volume from the pycnometer's total volume to find the powder's volume. * Divide the powder's mass by its volume to get its density. Professional Density Measurement * (12:37) U-tube density meters are digital instruments that use vibration to precisely measure liquid density. * Fast and accurate, but expensive. * Now available for amateur use, but with limited density range (mostly for brewing). * (21:39) Gas pycnometers use gas displacement to measure the volume of powders, even porous ones. * Accurate and versatile, but expensive. General Tips * Use a companion weight (11:49) to simplify mass measurements with a pycnometer. * When measuring powder density, choose a solvent with low solubility in the powder. * Saturate the chosen solvent with the powder to minimize errors due to dissolution. The video emphasizes that while density measurement might not be the most glamorous aspect of chemistry, it's a fundamental and valuable technique for characterizing substances and monitoring reactions. i used gemini 1.5 pro to summarize the transcript

The shade in the phrase “humans are very dense” is pitch black lmao 😂

There is no good reason for me to watch this but I did. I feel smarter, though not in a way that is useful for my practical day to day life experience. I do not feel that my time has been wasted.

I also used to get irritated when employers would ask me to evaluate tedious things. Once I was asked to evaluate several thermal interface materials for their performance, and vocally griped about it to my boss. I later realized how utterly fascinating all of this was. It's just how it goes in science sometimes. Thanks for the great content!

An entire series on metrology in chemistry would be nice. Especially the "this is good enough for home amateurs" observations. I personally tend to stress WAAAY too much over precision in calculations, despite not having the means to measure at the numbers of digits I'm fussing over.

Nurd Rage keep up these videos, one of the most credible sources of chemical techniques on YouTube and an added bonus you are a fellow Canadian!

genuinely excited to learn dude this is a topic i havent ever given much thought to thank you for the lesson :D

Its kinda crazy how much ive learned watching your channel for the past 14 years since i was a freshman in highschool, i wound up just doing HVAC lol. I still have a nice collection of mixed gold ive been piling up to turn into pure gold, im just waiting until i decide to invest in the proper equipment and build a ventilation hood.

1:14 you got me good with that one. Congrats !