Single spring balances

So far we have only mentioned spring balances, with a single pan. Chemical balances, with two pans, also have a place in our analysis. The difference is that in Equations 5 and 6 the entries in the matrix W can now take three values +1 if the object is placed in the left pan, -1 if it is in the right pan, and 0 if it is omitted from that measurement. 

Input is balanced by output in a steady-state system. The concentration of an element in seawater remains constant if it is added to the sea at the same rate that it is removed from the ocean water by sedimentation. Input into the oceans consists primarily of (1) dissolved and particulate matter carried by streams, (2) volcanic hot spring and basalt material introduced directly, and (3) atmospheric inputs. Often the latter two processes can be neglected in the mass balance. Output is primarily by sedimentation occasionally, emission into the atmosphere may have to be considered. Note that the system considered is a single box model of the sea, that is, an ocean of constant volume, constant temperature and pressure, and uniform composition. 

The simplest balance mechanism, readily adaptable to decomposition studies, is that based on measurement of the extension of a quartz spiral spring. Quartz crystal microbalances can be used for very sensitive measurements [84] (e.g. on single crystals) but the temperature range is limited. 

Sash balance- A device, usually operated by a spring and designed to hold a single hung window vent up and in place... 

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