Hi everyone,
I need to calculate the Hausner Ratio of my samples. My limitation is such that I don't have much powder for each sample (approx 5cm3), I have been able to get a Tapped Density Tester with a cylinder of 5 ml but how can I measure the bulk density of the samples with such a small quantity?
Would it work if I use a graduated cylinder and weigh the powder?
Any suggestions will be greatly appraised.
With thanks,
Nadiir
You can use small Pycnometer to measure the bulk density of you powder.
The formula d = M/V works only when you do not have porosity in your sample. If you have powdered ceramic sample, you must compress it till you get zero porosity which is not easily possible. Even if you do hot pressing to make pellet, porosity will not be zero. The exact density can, therefore, not be calculated by this simple formula in case of powders. Error will depend on porosity content.
Pycnometry is a good technique. Alternatively, liquids having different density can help to measure the density (flotation)
with great quantity, you can obtain bulk density more representative than that with small amount.
Definitely, no. It is better use a pycnometer.
Using d= m/V, you will have high porosity in the volume determination and the density would be measured in a wrong way.
I would also recommend for the powders a pycnometer either automatic or glass.
You can use small Pycnometer with alcohol known its denisity to measure the bulk density of you powder first determine the mass of pycnometer M1 then mass of pycnoeter and an sample M2 the mass of the sample M3= M2-M2 then added the alcohol in the pynometer to the remark and determine the mass M4 the mass of alcohol M5= M5-M2 determine of volume of alcohol V1= M5/density of alcohol then volume of the sample powder = volue of pychnometer - voluem of alcohol =V2 and then the density of the sample = V2/M3
Dear Prof. Shalabi,
Thank you for your response and detailed calculation. I'll look into it as suggested.
Many Thanks.
Dear everyone,
After having consulted your suggestions, I could find the reasoning behind using a pycnometer.
I have found this link useful on determining the different densities using the Gas Displacement Pycnometry System by Micromeritics Instruments. I'd thought to share it here.
http://micromeritics2.reachlocal.com/?scid=1229585&kw=7895020&pub_cr_id=6234969370
Thank you all.
Kind Regards,
I also vote for the method suggested by Mr.Shalabi, but in my opinion instead of using fixed volume picnometer you can use any known volume vessel to perform the measurement. Fastest homemade would be to use syringe although some additional measurements would be required to check the accuracy. Optical reading can be enhanced significantly when using pocket camera to zoom in and quantitize the reading. Syringe can be filled with needle through the in/outlet with alcohol without moving the piston.
Alcohol is good choice to almost all materials if they are wetted properly and do not react. Alcohols can be then evaporated easily.
Have not done this, but sounds reasonable.
Dear Gergo,
Thank you for sharing your idea here. It sounds easy, indeed. In my case, my sample is insoluble in alcohol and doesn't reach neither.
A specific gravity bottle (a liquid pycnomneter as opposed to gas pycnometer) - used to be caled an Archimedes bottle in my day - is ideal for small quantities of material and would measure the real density of the material. Plenty of links on Google. It's an inexpensive route for what you want to acheive.
I don't think that a pycnometer will be of any use to you, since you require the bulk density, not the particle density. In fact you need the free settled and tapped bulk densities.
The Hausner ratio is not a precise number. It is only an indicator for such properties as the flowability. It will vary depending on the method of measurement. Don't get too tied up with the accuracy.
You will simply have to use a small vessel such as the measuring cylinder that you propose to measure the free settle bulk density. There is little else that you can do.
Thank you both for sharing your opinions over here.
Indeed, I am looking for the freely settled/bulk density of the powder to evaluate the flowability using the Hausner ratio. I'll give the simple approach a try and see what it gives before investigating the other proposed methods.
Best Regards.
To determine Hausner ratio you need to measure BULK density (from the volume of particles PLUS voids) in two conditions as Peter identified. The first, the unsettled/loose volume (density) can be done in the small measuring cylinder... indeed no worse than the second condition... the settled/tapped volume(density) in the same small cylinder.
The greater uncertainty is always in the starting (untapped) volume since that volume will change relatively rapidly even with just a few taps. You can tap for hundreds/thousands /tens of thousands and the end point won't change. The starting volume is always user dependent and often poorly repeatable because of different "fluffed" starting state, roughness of handling the cylinder when filling and mounting on device.
It is for this reason many workers use a Scott volumeter to obtain the lowest practically achievable loose density. Easy enough to find details on the web, but with such small amount of material you would need to use a custom-fabricated receiving cup.
You might also like to determine not just a single Hausner ratio from just two numbers (start and finish), but to measure tapped volume as a function of number of taps (use a geometric progression e.g. 1,2,5,10,20,50 etc) then apply the Kawakita equation. Let me know if you have trouble tracking it down.
Many thanks for your detailed answer, Dr. Martin. I've noted down the Kawakita equation as well.
Kind Regards.
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