Primer on Density and Volume

Density and Volume are two critical concepts for anyone working the lab.  Usually this is taken for granted when you move on to more complex experiments.  For those who have some doubts about these two aspects this primer document explains the basic methods used to determine density and volume of various objects and then provides instructions for experiments that can be used to experimentally understand these concepts.  The essential procedure for determining density is simple. Calculate the mass of the object (usually using an analytical balance) and then divide it by its volume.  This will give you density.  There are of course various use cases where the mass and volume are not directly measurable and you will need to use indirect means.  The document touches on these aspects as well.

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Using an Analytical Balance in the Measure of Molar Mass of Condensed Vapor

Determining the molar mass of condensable vapor may seem impossible if you don’t know how. This document explains the procedure in simple terms.  The process involves adding excess of the liquid that corresponds to the vapor to a weighed bulb.  This is then heated.  Once heated all the liquid in the bulb gets volatilized and the excess vapor is expelled.  Next the bulb is cooled and the weight of the bulb with the condensed vapor is measured. The condensed vapor’s mass is equal to the the vapor’s mass found in the flask at elevated temperature and the existing pressure.  This can then be used to calculate the moles present and the liquid’s molar mass from the “ideal gas law”.  Equipment used includes: ring stand, hot plate, analytical balance, beaker, flask, tap water, aluminum foil and 5 ml of an organic fluid that is volatile.

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Brief Instructions on Using An Analytical Balance Correctly

Here is another short but precise set of instructions for using the analytical balance.  The key points to note are: the location where you set up the analytical balance should be free of ambient air currents and it should be free of vibrations as both these factors will have a negative impact on the readings.  Not mentioned is the possibility of using a vibration dampening table – typically a counter top made of some heavy material like marble and rubber studs on the legs to absorb the vibration.  This would be useful in places where it is not possible to avoid vibrations entirely.  The other instructions are also relevant: be careful not to disturb the balance after taring (or zeroing) the balance, use weighing dishes, tongs, or gloves as needed, cool hot objects, weigh hygroscopic materials rapidly due to their tendency to absorb water, and always use the same procedure … Read the rest

Using the Analytical Balance in the Chemistry Lab

Balances are crucial to nearly everything done in the chemistry lab.  Thus it becomes all the more important that you know how to work with them.  This primer on using different types of balances is a good place to start. Targeted at beginners in analytical chemistry it explains the use of the analytical balance, the proper method of weighing on an analytical balance, and the precautions to take when using the unit.  Accompanied by detailed pictures on handling various lab equipment, it gives a visual cue to the detailed explanations on how to use the balances safely and properly for accurate results.

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Using An Analytical Balance for Beginners

Here is an introductory lesson that you can use in the lab to learn how to weigh samples with an analytical balance. There are two exercises described in the document.  The first one analyzes the percentage of water in a hydrate while the second one does a statistical analysis to determine the mass of a penny.  Both exercises are good for practice that will expose the user to a wide range of functions in the analytical balance.  The document describes both the objective of the experiment as well as the procedure to be followed.  The complete experiment is spread over a three week period.

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Fortification of Wheat Flour with Iron

One of the most common micro-nutrient deficiencies affecting both the developed and developing world is anemia.  While it’s presence is markedly lower in the developed world, it is nevertheless a major cause for concern in the developing world.  One approach to combating anemia is to fortify wheat flour with iron as explained in this document.  While iron fortification won’t be the cure all for anemia it is nevertheless a major stepping stone.  The document is second part in a three part publication that: looks at the need for iron fortification and gives an over view of the entire program (part 1), provides operational and technical guidelines including the use of scientific digital scales for accurate measurement (part 2), describes analytical methods to monitor the fortification in wheat flour (part 3).

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Analytical Balance Used in Testing for Gold in Rat Blood (Clinical Study)

This could be treated as one of those ‘I kid you not’ posts. Here is a study analyzing Gold in Rat’s blood.  While on the surface it might look some weird science fiction movie, there is some seriously hard science underlying this experiment.  Gold nanoparticles are finding uses in the treatment of cancer.  This method is part of the an overall clinical study with this end objective.  The rat’s blood comes in to the picture as this is the early phase of testing on ‘small animals’.  At a later date the test will move on to human subjects.  The analytical balance is used to precisely weigh samples prior to testing.

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What to Look For in Heavy-Lifting Crane Scales

Kern HTS Crane Scale

Kern HTS Crane Scale

Crane scales are the heavy lifters across a broad spectrum of industries. Digital crane scales manufactured by Kern and available from Tovatech pack useful features in a compact package for precision weighing in manufacturing, shipping, scientific, educational, commercial and warehousing operations.

For example, the Kern HTS series of industrial crane scales is available in seven models from 150 to 10,000 kg capacities and readouts from 50 to 5000 g.  All models feature wireless infrared remote control operation with all functions housed in a battery-powered numeric keypad having a range of approximately 15 meters (50 feet).

Useful Features in a Digital Crane Scale

The HTS weighing mechanism is powered by a battery pack providing up to 150 hours of operation.  A charge condition indicator will signal when it is due for recharging.   Weights are indicated as kilograms or pounds on an easy-to-read LED display showing gross, tare and net weight.  To … Read the rest

A GLP Compliant Precision Scale is Mandatory for Recipe Weighing

A sous chef exercising a bit of creativity when following a recipe for a dessert might discover a significant improvement in the final product.  Or maybe not.  Such creativity is to be fully avoided when compounding drugs or other products where strict control of ingredients is mandatory.  A precision balance employed for the purpose of recipe weighing and record keeping is the tool of choice in applications where regulatory compliance and lab efficiency are goals.

Recipe weighing using  precision scales such as the Kern PCB available from Tovatech also supports research in labs where technicians create and vary formulations while seeking to develop new or improved products.… Read the rest

A Primer on Precision Scale Calibration and Test Weights

Precision digital scales and analytical balances must be recalibrated for accuracy to be in compliance with international standards and to maintain good laboratory practices.  Analytical balances such as the Kern ABJ series can be recalibrated using internal motor-driven weights.  The internal calibration sequence is initiated manually.  Semi-micro analytical balances such as the Kern ABT series automatically recalibrate using internal weights under four scenarios:  1) Four hours after the previous calibration; 2) When there is a fluctuation in temperature of 0.5oC (0.9oF); 3) When the balance is switched from standby to weighing mode and condition (1) or (2) has been met or 4) If the balance was disconnected from its power source.

Other scales require external recalibration, which is performed by using test weights under procedures that should be spelled out in your company’s Quality Management manual.… Read the rest