Anachem

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a measurement science consisting of a set of powerful ideas and methods that are useful in all fields of science, engineering, and medicine.

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Analytical Chemistry

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establishes the chemical identity of the species in the sample.

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Qualitative Analysis

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determines the relative amounts of these species, or analytes, in numerical terms

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Quantitative Analysis

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are the components of a sample that are determined.

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Analytes

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determine the mass of the analyte or some compound chemically related to it.

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gravimetric methods

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measure the volume of a solution containing sufficient reagent to react completely with the analyte.

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volumetric method

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measure electrical properties such as potential, current, resistance, and quantity of electrical charge.

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electroanalytical method

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we explore the interaction between electromagnetic radiation and analyte atoms or molecules or the emission of radi- ation by analytes.

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spectroscopic method

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if its constituent parts can be distinguished visually or with the aid of a micro- scope.

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heterogeneous

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is the process of determin- ing how much of a given sample is the material by its indicated name.

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Assay

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is the process of collecting a small mass of a material whose composition accurately represents the bulk of the material being sampled.

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Sampling

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are portions of a material of approximately the same size that are carried through an analytical procedure at the same time and in the same way.

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Replicate samples or replicates

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is a species that causes an error in an analysis by enhancing or attenuating (making smaller) the quantity being measured.

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interference or interferent

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is the collection of all of the components in the sample containing an analyte.

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matrix or sample matrix

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is the process of deter- mining the proportionality between analyte concentration and a measured quantity.

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Calibration

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The process of continuous measurement and control is often referred to as

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feedback system

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is the most common type of analytical balance, and it has a maximum load of 160 to 200 g and a precision of 0.1 mg.

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Macrobalance

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has a maximum load of 10 to 30 g and a precision of 0.01 mg.

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semimicroanalytical balance

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has a maxi- mum load of 1 to 3 g and a precision of 0.001 mg, or 1 μg.

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microanalytical balance

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The single-pan balance is currently being replaced by the

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electronic analytical balance

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means to cause an object to float in air.

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levitate

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is a device in which a small electric signal causes a mechani- cal system to return to a null position.

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servo system

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In each, the pan is tethered to a system of constraints known collectively as a

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cell

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The cell incorporates several ________ that permit limited movement of the pan and pre- vent torsional forces (resulting from off-center loading) from disturbing the align- ment of the balance mechanism.

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flexures

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______ is the mass of an empty sample container.

______ is the process of setting a balance to read zero in the presence of the tare.

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Tare, Taring

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Electronic balances generally feature an automatic _______ that causes the display to read zero with a container (such as a boat or weighing bottle) on the pan.

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taring control

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the cycle of measurement, comparison, and control is called

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feedback loop

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______ in a mechanical balance are prism-shaped agate or sap- phire devices that form low-friction bearings with two planar surfaces contained in _______ also of agate or sapphire.

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two knife adges, stirrups

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Single-pan balances are also equipped with a

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beam arrest and pan arrest

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is mounted near the end of the beam opposite the pan.

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air dumper

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_______ is specially treated through a process called _______

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Glassine paper, Calendering

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process begins with breaking down paper pulp fibers by beating. The beaten pulp is then squeezed into molds and dried into sheets. These sheets are then rolled through an al- ternating series of hot steel and fiber rollers called

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supercalender

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which is a small transparent screen mounted on the beam, is scribed with a scale that reads 0 to 100 mg.

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reticle

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is the weighing error that develops when the object being weighed has a significantly dif- ferent density than the masses.

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buoyancy error

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for determining masses that do not require great accuracy.

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auxiliary laboratory balances

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is a process in which a solid is cycled through heating, cooling, and weigh- ing steps until its mass becomes con- stant to within 0.2 to 0.3 mg.

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Drying or ignition

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are convenient for drying and storing solids.

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weighing bottles

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This process involved heating each cru- cible and sample cautiously over an open flame until the sample stopped smoking.

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Dry ashing

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is a principal advantage of using plastic weighing bottles rather than glass, but plastic abrades easily and is not as easily cleaned as glass.

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Ruggedness

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is a device for drying substances or objects

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dessicator

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serve only as containers

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simple crucible

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serve not only as containers but also as filters.

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filtering crucibles

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crucibles are manufactured in fine, me- dium, and coarse porosities (marked f, m, and c).

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sintered glass (fritted glass)

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has a perforated bottom that supports a fibrous mat.

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Gooch crucible

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an important filtering medium.

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Paper

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can be used to dry a precipitate that has been collected on ashless paper and to char the p

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ordinary heat lamp

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convenient sources of intense heat.

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Burners

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is capable of maintaining con- trolled temperatures of 1100°C or higher.

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muffle furnace

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The amount of arsenic in each sample was determined by measuring the intensity of the red color formed in the cu- vettes with an instrument called a

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spectrophotometer

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is the process of pouring a liquid gently so as to not disturb a solid in the bottom of the container.

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Decantation

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The last traces of precipitate that cling to the inside of the beaker are dislodged with a

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rubber policeman

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is a process in which a solid moves up the side of a wetted con- tainer or filter paper.

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Creeping

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used when a filtering crucible can be used instead of paper. The trap isolates the filter flask from the source of vacuum.

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vacuum filtration train

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The_____ is one cubic decimeter. The ____ is 10*-3L

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liter, milliliter

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permit the transfer of accurately known volumes from one container to another.

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pipets

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delivers a single, fixed volume between 0.5 and 200 mL.

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volumetric or transfer

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are calibrated in convenient units to permit delivery of any volume up to a maximum capacity ranging from 0.1 to 25 mL.

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measuring pipets

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measuring pipets, make it possible to deliver any volume up to the maxi- mum capacity of the device.

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Burets

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are manufactured with capacities ranging from 5 mL to 5 L and are usually calibrated to contain (TC) a specified volume when filled to a line etched on the neck.

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volumetric flasks

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a spectrophotometer provides a num- ber called

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absorbance

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is the curved surface of a liquid at its interface with the atmosphere.

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meniscus

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is the apparent displacement of a liquid level or of a pointer as an observer changes position. Parallax occurs when an object is viewed from a position that is not at a right angle to the object.

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Parallax

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is a measured fraction of the volume of a liquid sample.

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aliquot

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is needed to record measurements and observations concern- ing an analysis.

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laboratory notebook

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The qualities required of a _____, in addition to extraordinary purity,

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primary standard

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This agency also prepares and sells _______, which are complex substances that have been exhaustively analyzed

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reference standards

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is the sudden, often violent boiling that tends to spatter solution out of its container.

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Bumping

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is the oxidation of the organic constituents of a sample with oxidizing reagents such as nitric acid, sulfuric acid, hydrogen peroxide, aque- ous bromine, or a combination of these reagents.

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wet ashing

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has a maximum capacity that ranges from 1 g to several kilograms and a precision at maximum capacity of at least 1 part in 105.

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Analytical Balance