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Laboratory Orientation and Testing of Body Fluids and Tissues for Forensic Analysts


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The term "weight" is commonly used synonymously for mass. Mass is the amount of matter in an object, and the International System of Units (SI) unit for mass is the kilogram (kg).02

A discussion and demonstration of the use of all types of balances in the laboratory, such as top-loaders and analytical balances, should be provided. If necessary, a review of basic math and standard measurements can be presented. Traceable standards, such as weight sets, are easily obtained for this purpose, or a laboratory may employ an outside entity to conduct the calibration. It should be noted that the outside entity must use traceable standards to conduct the calibration. A balance should be calibrated whenever it is moved.

Image of top-loading balance
National Institute of Justice (NIJ) (see reuse policy).

Top-loading Balances

Top-loading balances are generally portable and ideal for easy weighing tasks. They have a larger weighing pan and may offer ranges such as 210g x 0.01g and 8100g x 1g, and are thus applicable for weighing chemicals to make stock reagents, etc. It is imperative that anyone using a balance know how to properly use features such as the external calibration and taring functions.

Analytical Balances

Analytical balances offer higher resolution and measuring quality, in ranges typically to 2.1g x 0.001mg and 510g x 0.1mg. Such tools are necessary in the preparation of some reagents in the forensic biology laboratory.


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