How to Weigh a Powder on a Precision
Mass Balance
Introduction:
In physics, chemistry, and engineering, using the mass of an object in calculations is essential
when predicting outcomes of various events. Classically, obtaining the mass of an object was
performed on a balance, where the mass of that object was compared to a different object of
known mass. Today, humans have the ability to obtain a mass on an electronic precision mass
balance, which gives results of extreme accuracy and precision. In today’s world, it is very
important to obtain accurate masses with significant figures - digits of known accuracy – on the
milligram scale as a bare minimum. In one application, measuring the mass of powders can be
extremely messy since they are made of extremely fine particles (approximately one micron in
diameter). If dumped, powders can be hard to clean up due to their ability to deposit everywhere,
and powders can be extremely dangerous if inhaled. In order to safely and effectively obtain the
mass of a powder using a precision mass balance, one can follow the procedures below.
Required Items:
Safety Equipment:
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1 Lab Coat
1 Pair of Latex Gloves
1 Pair of Safety Glasses
1 Nose/Mouth Air Filter
Independent on Number of Samples:
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
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1 Precision Mass Balance
1 Permanent-ink Writing Utensil
1 Laboratory Notebook
Appropriate Solid Waste Disposal Container(s)
1 Spatula
Scotch Tape
1 Paper Towel
Kin Wipes
Dependent on Number of Samples:


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Sample(s) to be Weighed
1 Storage Container per Sample to be Weighed
2 Sheets of Weigh Paper per Sample to be Weighed
1 Label per Sample to be Weighed
IMPORTANT KEY TERMS:
Nose/Mouth Air Filter: This
mask should cover the mouth
and nose and contain a filter.
An example can be found in
Figure 3.
Appropriate Solid Waste
Disposal Container(s): These
are laboratory procedure
specific, and they should be
provided by the laboratory
manager.
Kin Wipes: These are tiny
paper towels that contain little
impurities (like paper towels
do) in order to accomplish
required cleanliness.
Figure 1:
Displays a
way to set
up an
organized
laboratory
Preparation:
1. Gather all of the required items and conveniently place them
according to Figure 1.
2. Lay down a paper towel on top of the work bench where active
samples will be placed. The paper towel should contrast the powder,
and it will be used to detect any spillage of the powder.
3. Using a pen, clearly label (on the paper towel) where each sample will
be placed.
If the composition of the samples vary, use that to classify each
powder; if a specific mass of each sample is to be weighed, use
that to classify each powder, and if the same powder is to be used
with random masses, label the samples “Sample 1…Sample 2…
…Sample N” and coordinate with the laboratory notebook.
4. If powder samples must be placed in narrow-necked
containers, make weigh paper funnels by using the
procedure below:
a. Grab a piece of weigh paper by two corners along the
same edge of the paper as in Figure 2a.
b. Fold one of the corners over (without creasing) to the
center of the weigh paper as in Figure 2b.
c. Fold the second corner over the previous fold as in
Figure 2c. Adjust this placement so the smaller
opening is a diameter such that it will fit inside the
neck of the container.
d. Tape the funnel to the container so the powder can
be poured in the wide end and enter the jar through
the narrow end.
e. Repeat steps (a)-(e) for each funnel.
5. Put on all safety equipment as shown in Figure 3.
WARNING: Throughout the entire
Preparation process, be sure all
samples are SEALED. Convection
currents in the room cause
powders to be volatile, which can
be hazardous to health if inhaled
or contact the skin. Consult the
Material and Safety Data Sheets
(MSDS) of all powders use and
be aware of the hazards.
2a.
2b.
2c.
Figure 2: Provides a step-by-step
visual on how to make a weigh
paper funnel
Figure 3:
Appropriate
safety
equipment wear
when working
with powders.
Obtaining a Mass – Repeat for Each Sample
1. Crease a piece of weigh paper and place it on the silver scale of
the mass balance as in Figure 4.
2. Close the doors on the mass balance to eliminate room convection
currents, and press the button reading “Tare” or “Zero” in order to
calibrate the mass balance. The calibrating process may take
several seconds to complete.
3. Open the doors of the mass balance and unseal the powder
sample.
4. Using one hand for the spatula and the other hand for holding the
vail containing the sample, place each hand through a window on
the mass balance as in Figure 5. This will reduce sample spillage
and increase convenience.
Figure 4: How to
crease the weigh
paper and put it
on the mass
balance.
NOTE: After calibrating the scale, the
reading may begin to fluctuate.
This occurs from static due to
charge buildup. Use a charge gun
to neutralize the charge, or use
aluminum foil on the silver scale
instead of weigh paper.
Figure 5: How
5. Use the spatula to scoop powder from its holding container to the
to effectively
weigh paper. Do NOT dump the powder directly onto the weigh
use the
paper; it is harder to take powder off of the scale than to put it on.
spatula to
6. If too much powder is placed on the scale, follow the procedure
measure a
below:
sample
a. Use the spatula to create a pile of powder on the
crease as in Figure 6a.
b. Use the spatula again to pick up powder and
Figure 6: How
place it in the container as in Figure 6b.
to scoop a
7. In order to obtain a desired mass with high precision,
sample off of
follow the procedure below:
the weigh
a. Obtain a mass slightly below that of the desired
plate
weight.
b. From the container, place a small amount of powder on
the spatula.
6a.
6b.
c. In order to remove all of the powder from the spatula onto
the scale, bump the spatula against the side of the mass
WARNING: When bumping the
balance.
spatula against the side of the mass
d. If too much powder is accidentally placed on the scale,
balance, make sure the powder falls
on the weigh paper. If any powder
refer back to Step 6.
gets on the silver tray itself, the mass
e. Remove hands and close both doors to obtain a final
will be inaccurate. The mass balance
weight.
will then need to be cleaned, and it
8. After the desired mass is obtained, record the mass in the
will be necessary to start from Step 1.
laboratory notebook, pick up the weigh paper according to Figure
7, and dump it into the funnel attached to the storage container.
Be sure to perform this step over the paper towel, and label the
Figure 7: How
vial with the sample name.
to pick up
9. Remove the funnel and
weigh paper
10. Wipe off the spatula with a kin wipe and repeat from Step 1 for
containing a
powder
each additional sample.
Clean-Up
1. Clean all powder spillage off of the mass balance using kin
wipes.
2. Clean the spatula with distilled water, ethanol, and then
distilled water again. Dry the spatula with kin wipes, and if
necessary, place the spatula in a drying oven.
3. Identify all materials containing powder and place them in the
correct disposal container(s).
4. Remove all protective equipment.
5. Replace all leftover materials to their original places.
6. Wash hands thoroughly.
WARNING: Throughout the entire
Clean-Up process, be sure all samples
are SEALED. Do NOT remove any
safety equipment until all of the
powder has been cleaned up and
disposed of correctly. Remember,
powders are volatile and can be
harmful if inhaled or contact the skin.
Consult MSDS for questions about
chemical hazards.
Written by: Blake Burger