CHEMISTRY GLOSSARY

Knudsen number    →   Knudsenova značajka

Knudsen number (Kn) is a dimensionless quantity used in fluid mechanics, defined by

where λ is mean free path and l is length.

Euler number    →   Eulerova značajka

Euler number (Eu) is a dimensionless quantity used in fluid mechanics, defined by

where p is pressure, ρ is density, and v is velocity.

Lewis number    →   Lewisova značajka

Lewis number (Le) is a dimensionless quantity used in fluid mechanics, defined by

where a is thermal diffusivity and D is diffusion coefficient.

Mach number    →   Machova značajka

Mach number (Ma) is a dimensionless quantity used in fluid mechanics, defined by

where v is velocity and c is the speed of sound.

Froude number    →   Froudova značajka

Froude number (Fr) is a dimensionless quantity used in fluid mechanics, defined by

where v is velocity, l is length, and g is acceleration due to gravity.

Knudsen burette    →   Knudsenova bireta

Knudsen's automatic bulb-burette, developed by the Danish physicist Martin Knudsen (1871-1949), is designed in a way that even routine field analysis in a boat laboratory would provide highly accurate measurements. The burette is filled with a mixture of silver nitrate from reservoir R, located above the burette, by opening the A valve. When the solution crosses the three-way C valve the A valve is closed preventing further solution flow in to the burette. Any extra solution is caught in the W bowl. Turn the C valve, which marks the zero on the scale, in order to allow atmospheric air to enter the burette. Since most open-ocean samples lie in a relatively small chlorinity range, the burette is designed so that much of its capacity is in the bulb (B). This allows the titration to be quick (by quickly releasing contents from the B area) and reduces the error that occurs from the slow drainage along the inner wall of the burette.

Each millimeter is divided in to twenty parts (double millimeter division of the Knudsen burette) which allows for highly accurate measurements (the scale is read up to a precision of 0.005 mL). From 0 to 16 the burette isn't divided, that usually starts from 16 and goes until 20.5 or 21.5. A single double millimeter on a Knudsen burette scale corresponds to one permille of chloride in the seawater sample. This burette can be used for titration of water from all of the oceans and seas, with the exemptions being areas with very low salinity (e.g. the Baltic Sea) and river estuaries which require the use of normal burettes.

Knudsen’s pipette    →   Knudsenova pipeta

Kudsen's automatic pipette, developed by the Danish physicist Martin Knudsen (1871-1949), allows quick and accurate transfer of a constant volume of liquid (sea water), usually around 15 mL. On the top of pipette is a double sided C vent that can establish flow between the body of the pipette and one of the branches (A or B), or isolate the body of the pipette from both of the branches. Sucking through the B branch the pipette is filled with liquid, it is closed with a twist of the C valve and the liquid is released by rotating the valve towards the A branch (so atmospheric air can enter the pipette). Emptying the pipette takes around 30 seconds. Before it's first use, the pipette must be calibrated with distilled water.

Strouhal number    →   Strouhalova značajka

Strouhal number (Sr) is a dimensionless quantity used in fluid mechanics, defined by

where l is length, f is frequency, and v is velocity.

Nusselt number    →   Nusseltova značajka

Nusselt number (Nu) is a dimensionless quantity used in fluid mechan-ics, defined by

where h is coefficient of heat transfer, l is length, and k is thermal conductivity.

Peclet number    →   Pecletova značajka

Péclet number (Pe) is a dimensionless quantity used in fluid mechanics, defined by

where v is velocity, l is length, and a is thermal diffussivity.