WEIGHING IN THE LABORATORY

Introduction
2.0 Objectives
3.0 Main Content
3.1 Types of Weighing Balances
3.2 Weighing
3.3 Weighing on an Analytical Balance
3.3.1 Planning
3.3.2 Checking the Balance
3.3.3 Balance Environment
3.3.4 Calibration
3.3.5 Balance Uncertainties
3.3.6 Rules for Weighing
3.3.7 Weighing by Difference to Overcome the Problem
of Balance Calibration Errors
3.4 Sample Weighing Experiment
3.4.1 Using the Top-Loading Balance
3.4.2 Using the Analytical Balance
3.4.3 Weighing by Difference using the Tare Function of
the Analytical Balance
3.5 Report Sheet
4.0 Summary
5.0 Conclusion
6.0 Tutor-Marked Assignment
7.0 References/Further Reading
1.0 INTRODUCTION
Weighing scale is very fascinating and interesting. These did not come
to existence overnight, they evolved from a barter system where units
were absent compared to the modern day standards. When the standard
units were accepted by businesses and governments across different
regions, an industrial revolution was set to begin and everyone benefited
from that. Today the old age classical weighing scales have become
obsolete but they served the humanity for a long time. In the modern
times, one can see the weighing scales ruling the industrial and domestic
space.

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2.0 OBJECTIVES
At the end of this unit, you should be able to:
• identify different equipment used in laboratory weighing
• differentiate between a to top-loading balance and an analytical
balance
• carry out simple weighing experiments in the laboratory.
3.0 MAIN CONTENT
3.1 Types of Weighing Balances
Here is a list of different products that you should know about.
Fig. 1.1: Iron Scale
1. The conventional wooden or iron scale was the oldest weighing
machine invented by man. It consisted of two containers attached
to each other through a pulley system. These weighing scales
were meant for domestic purposes and they often reported wrong
measurements. It was more of a weighing balance than a
weighing scale.
2. The next stage was the spring balance. A spring connected to a
fixed and rigid system that was used to weigh mass of objects by
hanging them with the spring. The spring will develop tension in
it and it will reflect a standard value on the rigid body attached to
it. The value will reflect the weight of the object in standard unit
of mass. Precision and accuracy were still missing in this case.
Fig.1.2: Spring Balance
3. The modern digital weighing scales are the third kind of
weighing machines invented so far. These are the products that
are electronically operated and display results very precisely.
They have many types, styles and weigh ranges. Broadly, they
can be categorised into two categories namely; Industrial Scales
and Domestic Scales.

Fig. 1.3: Digital Weighing Scales
4. Hydraulic Scales are used mainly in the laboratories and
industrial units. It made use of liquid displacement technique to
weigh the mass of heavy objects. The object placed on the top of
weighing panel displaces the liquid and the volume change
indicates the weight of the object.
Today, the weighing scales have changed a lot over a course of time.
Most of the modern invented equipments are precise, accurate and
minimize the errors while weighing. These weighing machines
constitute of electronic circuits, digital chips, electronic sensors and
motion sensors. They are portable, lightweight and easy to operate and
even an unskilled person can operate these devices.
3.2 Weighing
When mass amounts are specified in chemical procedures the following
terms are commonly used:
a. "Weigh out about 2g of ...... ". This statement means that you are
required to weigh an amount of approximately two grams. The
accuracy to which this mass amount needs to be known is not
high and the top-loading balance will suffice.
b. "Accurately weigh out about 0.2g of ....". This statement means
that you should, with the aid of the analytical balance, weigh out
an amount that is close to 0.2 g, but you must know the exact
amount to an accuracy of ± 0.1 mg. Note that this does not mean
that you must weigh out exactly 0.2000 g. An amount between
0.1900 g and 0.2100 g is perfectly acceptable. However, you
must know the exact amount to the nearest tenth of a milligram.
When weighing out triplicate samples, it is not necessary that all
three weights be exactly the same, indeed, it is poor procedure to
attempt to do so.

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In this unit, you will be asked to make a variety of weighing. It is
important for you to realise with what sort of accuracy these weighing
should be made. Depending on the desired accuracy you should use the
proper balance to make your weighing. There are two types of balances
available to you in this course:
A. The Top-Loading Balance
The top-loading balance digitally displays a mass reading, in grams, to 2
decimal places. The uncertainty in a single reading on the top -loading
balance is 0.05g.
B. The Analytical Balance
The analytical balance is more accurate than the top-loading balance. Its
digital display gives mass, in grams, to 4 places after the decimal. The
uncertainty in a single reading on the analytical balance is ~ 0.0002 g.
You will use this balance if the experiment calls for accurate
measurement of mass. Never use the analytical balance if the toploading
balance will do. The analytical balances are usually located in
the “Balance room” of a laboratory.
3.3 Weighing on an Analytical Balance
Weighing is a frequent step in analytical procedures, and the balance is
an essential piece of laboratory equipment in most analyses. In spite of
this, weighing is a common source of error that can be difficult to detect
in the final analytical results. The procedure described here applies
directly to electronic balances; therefore, certain portions of the
procedure are not applicable to other types of balance. The weighing
procedure can be separated into three basic steps: planning, checking the
balance, and weighing the material.
3.3.1 Planning
The initial step is the proper to assembling of the equipment, such as
containers for weighing, receiving vessels, forceps, pipettes, spatulas of
proper size, and so forth. Use containers of size such that the loading
capacity of the balance is not exceeded. Make sure that the containers
selected to receive the weighed material are clean and dry. Assemble the
necessary chemicals if solutions or reagents are required. Preparation of
the material to be weighed is often necessary. The material may require
grinding or drying. Some materials may have been heated or stored in a
refrigerator. Materials must be brought to the temperature of the balance
before they are weighed. To avoid condensation of moisture,

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refrigerated materials must be allowed to come to room temperature
before the container is opened.
3.3.2 Checking the Balance
In the next step it is important to remember that, unless the balance is
checked before each weighing operation is performed, errors can easily
occur, resulting in faulty analytical data. The balance user should check
the balance environment, calibration, and balance uncertainties. Do
not assume that the balance has been left in the proper operating
condition by the previous user.
3.3.3 Balance Environment
The balance is placed in a suitable location with sufficiently low levels
of vibration and air current. It must have a constant electrical supply.
The balance and the surrounding work area have to be kept neat and
tidy. It is good practice to use a camel's hair brush or its equivalent to
dust the balance pan before any weighing so as to remove any materials
that may have been left by the previous operator.
NOTE: Individuals must clean up debris, dispose of any spilled
materials or paper, and remove the vessels and apparatus used in making
the measurements.
When a balance is moved, it must be allowed to adjust to the
temperature of its new environment and be recalibrated.
3.3.4 Calibration
If necessary, turn on the power, and allow the balance to equilibrate for
at least 1 hour before proceeding with the calibration. (Microbalances
may require up to 24 hours to reach equilibrium). If the balance power
has gone off and then has come back on, as in a power outage, certain
types of balance may display a message indicating that the balance must
be calibrated before a weighing is made. If the operator touches the
balance bar, the message may be cleared and the balance may display
zeros; however, the balance will not give the correct weighing until it
has been calibrated. Electronic analytical balances have an internal
calibration system based on an applied load. The calibration applies for
the current ambient temperature.
3.3.5 Balance Uncertainties
Drift Reduction: Drift is one of the most common errors, and it is also
one of the easiest to reduce or eliminate. Balance drift can be present
CHM 192 MODULE 4
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without the operators being aware of the problem. Check the sample, the
balance, and the laboratory environment for the following causes of
errors, and eliminate them when:
• a balance door is open
• temperatures of the balance and the material to be weighed are
not the same
• the sample is losing or gaining weight
• the balance has been recently moved but has not been allowed to
equilibrate to its surroundings or has not been recalibrated
• air currents are present in the laboratory
• temperatures in the laboratory vary
• the balance is not properly leveled
• laboratory operations are causing vibration
• hysteresis of the mechanical parts occurs during weighing.
3.3.6 Rules for Weighing
• Do not handle objects to be weighed with bare hands. Use tongs
or paper towels if no appropriate tongs are available.
• Never weigh chemicals directly on the balance pan; use a glass
container or weighing paper or filter paper.
• If you spill a chemical on the top -loading balance, clean it
immediately. Never spill chemicals inside the analytical balance
enclosure. Keep the weighing chamber and weighing pan clean.
• Before using the balance, be sure that the pan is clean. If it is
dirty report it to your instructor, then brush it off with the brush
provided.
• Do not overload the balance. The maximum capacity of the top -
loading balance is 620g. The maximum capacity for the
analytical balance is 110g.
• Do not weigh hot or cold objects on the balance. Hot objects will
give erroneously low readings due to buoyancy of hot air, while
cold objects will give high readings.
• Check to be sure that the balance is leveled. It is level if the
bubble in the Level Indicator is in the centre while the balance is
“OFF”. Your instructor may need to adjust the leveling Feet.
3.3.7 Weighing by Difference to Overcome the Problem of
Balance Calibration Errors
How accurate are your balance readings? There is no way for you to
know. In order to overcome the problem of inaccurate readings due to
lack of calibration or miscalibration, chemists designed a method called
weighing by difference. It does not matter how far off each reading of
your balance is if you weigh your sample by difference.

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For example: Weighing a solid sample by difference from a beaker: To
find the mass of the sample in the beaker, first the empty beaker is
placed on the balance and the mass is read. Then the solid is added to
the beaker and the mass of beaker with solid is read. The mass of the
solid sample is the difference between the two readings.
Notice that the weighing pan of the analytical balance is enclosed in
glass. This glass case is designed to protect the balance from
temperature fluctuations and air currents that cause the balance to drift -
that is, the digital display continues to change in one direction (up or
down). To make sure that the temperature of the air in the balance does
not change, keep your hands (which are warmer than the air in the
balance) out of the enclosure as much as possible, and keep the balance
doors closed.
Using Balance 1, a calibrated balance, the following masses are
recorded:
Mass of Empty Beaker: 24.7423 g
Mass of Beaker + Solid: 26.7587 g
Mass of sample: 26.7587g – 24.7423 g = 2.0164 g
Using Balance 2, an uncalibrated balance (all readings are low by
0.5000 g) the following masses are recorded:
Mass of Empty Beaker: 24.2423 g
Mass of Beaker + Solid: 26.2587 g
Mass of sample: 26.2587g – 24.2423 g = 2.0164 g
Does it matter which balance, 1 or 2, you choose to use?
_______________________________________________________
Explain:
__________________________________________________________
Throughout the weighing process you should protect the object you are
weighing from coming in contact with your hands by handling it with a
paper towel.

 DYNAMICS  in izotope 

Dynamics processing isn’t just about making things ‘louder’. In the context of mixing, dynamics processing can be used to control the dynamic range of an audio signal in order to achieve a variety of musical effects. You can think of dynamics processing as having two major ‘families’: Downward Compression/Limiting and Expansion/Gating. Using both of these two major types of processing to adjust dynamic range is often essential to creating the illusion of a perfect performance—or at least the polished sound of one! WHAT ARE DYNAMICS FOR? Using these processors is a way to control, reduce or expand the dynamic range or overall volume level of a track. In the case of compression and limiting, the goal is usually to “even out” the dynamic range of a track by attenuating loud transient peaks, such as a singer that suddenly belts out a high note in the middle of a gentle ballad, which can be a little jarring to the ear. In the case of expansion and gating, the goal is to lessen or remove unwanted signal on a track. Removing the sound of high hat bleed in a snare drum recording would be one example. Reducing the volume of unwanted breaths in a vocal recording would be another. iZotope’s Nectar 2 Production Suite includes a Breath Control module, which automatically detects and attenuates breaths in a vocal recording mo 19 PRINCIPLES OF DYNAMICS The ability of a good mixing engineer to use dynamics processing effectively is truly a life-long learning process. So let’s start with the four basic parameters common to almost all dynamics tools, namely, threshold, ratio, attack and release. Threshold The threshold is the level at which dynamics processing begins. For compressors and limiters, any signal rising above the threshold would be affected (see Fig. 1) For expanders and gates, any signal falling below the threshold would be affected (see Fig. 2). Figure 2 Figure 1 20 Ratio The ratio determines the amount of dynamics processing that happens to the signal. For example, a 4:1 ratio (see Fig. 3) on a downward compressor means that for every 4dB the signal in question rises above the threshold only 1dB will be heard above the threshold, a reduction of 3dB. A limiter is a compressor with a ratio of 10:1 or greater—often as high as 20:1 or 30:1—and generally a fast attack time (see below). In the case of a gate, the threshold is ∞:1, meaning that any signal below the threshold will be muted. Attack The Attack parameter defines how fast the dynamics processor works once the signal has passed the threshold, usually measured in milliseconds. Release The Release parameter determines how fast or slow the dynamics processor stops processing or “lets go” once the signal has passed the threshold, also measured in milliseconds. Compression essentially causes distortion in a signal, in that it changes the original sound of the signal through its processing. The compressor typically achieves this by emphasizing certain harmonics based on how the compressor is hitting the incoming signal. It’s our job to make that distortion feel transparent Figure 3 21 and to use our dynamics to create the best-sounding performance we can. One way to avoid adding more distortion is to be careful with our attack and release times—too fast an attack time can “choke” the performance and too fast a release time can cause the instrument to “pump”. Try setting these parameters and listen for yourself to hear the effect so you never do this again! In the picture below, the release time is too slow, and the compressor is squashing the signal before it has time to recover. See, that was easy! Now that we know our parameters, how do we use them effectively? We don’t necessarily want our track to be constantly compressed or squashed, so we should set our compressor to achieve the desired effect. But how do we know what the desired effect is? There is no hard and fast rule since much is determined by instrument type, style of music, performance, etc. We’ll go into more detail in Chapter 10: Mixing An Action Verb. For now, lets g 22 THE ART OF DYNAMICS PROCESSING • Use lower ratios (2:1–5:1) for “leveling out” performances, particularly ones that have a few notes that “jump out” in a particular performance. Sometimes, using two more gentle compressors in series (one compressor followed by another compressor) is a more transparent way of leveling out an audio track. Rather than one harsh pass of compression that could sound squashed, you achieve the same result with more finesse. In the picture below, we are compressing the same note as the previous picture, but both Compressors are engaged in series. 23 • Try using faster releases when compressing drums and other percussion instruments. This helps tame the transients (the initial burst of sound) but maintain the decay of the original sound. • On that note, be careful to not crush the transients of a particularly percussive or choppy transient audio signal with an attack time that’s too quick. • When compressing acoustic guitars, try slower attacks for a picked or plucked acoustic, and faster attacks for a strummed acoustic. Picked or plucked acoustics tend to have more individual transients that are louder than the sustain of the note. A faster attack will help to even out the attack and sustain. Strummed acoustics are generally more even dynamically, so a slower attack will help it “shine” a little more. • Distorted guitars already have some natural compression from overdriving the amplifier. For best results, use little to no compression unless there are spots in the performance that are popping out of context. • Try this on a lead vocal: first, set a limiter with a high ratio to grab the extremely hard notes and then follow it with a compressor using a gentler ratio (say 3:1) to do the overall processing. This will allow the compressor to not work as hard on those peaks, and the vocal will sound less ‘pumping’ and more natural.

Getting Started
Using Mastering Presets in Ozone 5
Ozone’s presets are designed to give you a quick
Every mix is different so no preset can perfectly master your project. However we have attempted to provide a wide range of presets that will help you find a good starting point for mastering your own material. By starting with a preset and using the Amount controls in Ozone’s interface, you’ll be able to tweak these presets to make them more closely fit the session you’re working on.
We recommend you download the Ozone Mastering Guide to learn the basic principles of mastering with Ozone. Presets can take you a long way, but learning how each of Ozone’s mastering modules works is key to getting the best results. You won’t regret it–your masters will sound better than ever before!
Setting Your Input Level
Setting the input level in Ozone can make a huge difference in how the dynamics modules in Ozone behave. Setting your input level is important when selecting presets as the presets will sound drastically different if your input level is too loud or quiet.
As a starting point try setting Ozone’s input level so that the input meter is peaking in the yellow area of the meter. It is OK if the input meter occasionally goes into the red when Ozone’s Loudness Maximizer is enabled, it will keep the audio from clipping.
Choosing a Starting Point
Start by listening through several of Ozone’s presets. You can start with a Genre-Based Mastering Preset or simply use the General Purpose Mastering presets. Because every mix is different, we’ve aimed to give you a lot of starting points so that you can choose the best one for your project. When you’ve found one that sounds like it has what your mix needs, you can start tweaking that preset to your liking.
Module Amount Controls
By starting with a preset you can subtly adjust the Amount Controls to help you get your mix closer to the way you want it to sound.
The Amount sliders are located at the bottom of Ozone’s interface. You can adjust them to control how much each of Ozone’s mastering modules affects your mix as well as how the module behaves. For example, turning down the Equalizer Amount slider can flatten out the EQ curve making the EQ’s effect less dramatic. Increasing the Maximizer Amount control will boost the overall level of your mix. There is also a Global Amount slider below the input and output level controls that allows you to quickly adjust how much Ozone’s modules process your mix overall.
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New Features in Ozone 5

If you're moving up from Ozone 4 to Ozone 5, we thank you for your continued support! Here are some changes and new features that you'll find in Ozone 5!
New Intelligent Workflow
Updated Interface
Ozone has been redesigned with a larger interface to make even more controls accessible on the front of the plug-in. Multibands are now color-coded with interface highlight colors that reflect the band you are currently viewing and/or adjusting a control for. The dynamics module now features a Show All Bands mode from which you can view and adjust all relevant settings for every dynamics stage of every band in one simple window. These updates allow for a more seamless workflow when performing multiband processing and streamline tasks that can be arduous in other plug-ins.
Module Presets
Ozone 5 has been updated with the added functionality to load and save presets for individual modules. You may apply settings to one module then mix and match presets from different modules to better address the needs of your mix.
New Intelligent Module Amount Controls
Ozone 5 now allows you to dynamically alter the settings of a module with configurable amount controls. This allows you to intelligently tweak the global settings of each individual module at any time from Ozone's main interface.
Meter Bridge and Meter Taps
Ozone 5 Advanced's powerful new Meter Bridge provides a full suite of audio analysis tools, perfect for visualizing changes made during the mastering process, troubleshooting problematic mixes, and comparing your mixes to reference tracks. Included Meter Tap plug-ins allow you to route audio streams from anywhere in your mix and compare them with the output of Ozone.
Component Plug-ins
Ozone 5 Advanced includes individual component plug-ins of each module in Ozone. Now you can selectively load individual modules into your session, each with their own dedicated module preset system.
New Processing Innovations
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IRC™ Loudness Maximizer/ Intelligent III Mode
Ozone 5 includes a new processing mode in the Loudness Maximizer called "Intelligent III". This mode is optimized to preserve transients, so they sound sharper and clearer in the output signal, even when aggressive limiting is taking place. The new Intelligent III Loudness Maximizer mode listens to incoming audio to determine how much limiting can take place before any detectable distortion occurs. Try this on your mixes and hear the difference.
Harmonic Exciter/ Triode Modes
We have updated the Harmonic Exciter to include new "Triode" modes. The Triode modes are modeled after tube circuits add the warm sound of a vintage preamplifier on up to four frequency bands, producing subtle dynamic and distortion effects.
Upward Dynamics processing and Soft Knee Compression
We have updated the Dynamics module to allow for ratios less than 1:1 at the gate, compressor, and limiter stage. This allows you to perform upward compression and upward expansion on your mix, giving you enhanced control of dynamic range. Additionally, we've added Soft Knee Compression to Ozone and Variable Knee Compression to Ozone 5 Advanced. Both allow you to perform more subtle and transparent compression on your mix.
Enhanced Hybrid Reverb module
New reverb processor utilizes both convolution technology to provide accurate early reflections of real acoustic spaces as well as algorithmic technology to give you greater control of your reverb’s late tails. Together the two technologies give you enhanced control to fine tune the reverb to your mix. Add subtle “room tone” without an obvious reverb effect or thicken a mix with longer reverb decay tim

What is Ozone?
A Complete Mastering System


Ozone is all you need to completely master your audio. Ozone 5 combines eight essential mastering processors into one complete system, letting you give your mixes a finished, full and professional sound.
Ozone’s critically acclaimed IRC™ (Intelligent Release Control) Loudness Maximizer gives you commercial volume and fullness without distorting or coloring your mix. Two independent eight-band Paragraphic EQs combine linear phase precision with the warmth and character of analog equalizers and even let you intelligently match your mix to reference tracks. Innovative multiband Dynamics, Harmonic Exciter and Stereo Imaging tools add depth and polish to your projects and because these modules are integrated in a single powerful interface, Ozone maintains the highest quality processing throughout the entire signal chain while also making the mastering process more efficient and intuitive than ever before.
What’s New?
Ozone 5 adds many quality and workflow improvements to every Ozone module, including new DSP algorithms and a wealth of visual tools to help you track and monitor changes made throughout the mastering process. Ozone Advanced includes additional processing tools in each module, a configurable Meter Bridge that can display relevant meter information in a separate, full screen window, and individual plug-ins for each of Ozone’s modules.
When you see a in the following documentation, this denotes a feature that is exclusive to Ozone 5 Advanced.
Key Features in Ozone
• Complete mastering system available in a single plug-in
• Includes eight essential mastering tools: Maximizer, two Paragraphic EQs, Dynamics, Stereo Imaging, Harmonic Exciter, Dithering, and Reverb
• Analog-modeled processing combined with linear phase precision
• Elegant, highly efficient user interface
• Extensive metering and visual analysis tools help you get better results
• Comprehensive preset system with over 100 professionally designed presets
• Module presets for mixing and matching settings between modules
• Integrated undo history with comparison tools
• User-definable signal routing
• Extensive automation support
• CPU-efficient and optimized for today’s low-latency DAW environments
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• Supports sampling rates up to 192kHz
Highest Audio Quality
Ozone uses highly optimized audio signal processing to achieve the highest resolution and sound quality possible. All of the mastering modules in Ozone are specifically designed to work together. By carefully matching crossovers and other internal processing, Ozone eliminates phase and artifact problems encountered when chaining together separate plug-ins. In addition, the sound quality and characteristics of each of the mastering modules is tuned to complement the others, providing consistent and high quality results.
Ozone uses analog modeling to give each of the mastering modules a smooth natural sound. For example, the equalizer recreates the soft limiting exhibited by a vintage valve equalizer, while the harmonic exciter mimics the musically pleasing harmonic saturation of a vacuum tube component.
Whenever there was a choice of CPU vs. sound quality, we chose sound quality. There are easier (less CPU intensive) ways of doing some of the processing that Ozone does, but the sound quality can suffer. Since Ozone is meant to be used for mastering, you would typically only have one instance of Ozone running on the main bus of a session, or in a 2 track editor, which should allow you to utilize Ozone even on lower powered CPUs.
Powerful Audio and Visual Feedback
We wanted to provide visual feedback wherever possible. Your ears and your eyes can be a powerful combination when you're mastering, and each processing module is complemented with useful spectrums, phase meters, and level histograms. Each module also has switchable views that highlight different aspects of how your mix is affected throughout mastering.
We also wanted to make it easy to get audio feedback by providing extensive solo/bypass controls and histories with functions for A/B comparisons. The Alt-click function on the EQ is an example of this as well. Wherever possible, we wanted to give you new ways to really hear what you are doing.
Intuitive Design and Easy to Use
We tried to make Ozone as easy and intuitive as possible from including a complete set of mastering modules in a single plug-in system, to context sensitive help, to the little things like mouse wheel support. There is a lot of power in Ozone, but we think that in no time at all you'll be making the most of it and getting great results with ease. Whether you’re a seasoned professional or you’re simply ready to take your productions to the next level, Ozone is the complete solution you need. Your mix isn’t finished until you put it through Ozone.
This help file is a quick reference for basic Ozone functions and controls. We have written a separate Ozone Mastering Guide that provides tips and techniques for mastering with Ozone.