NANSEN BOTTLES
type: Concept
in scheme: instruments
definition: Nansen bottles are 'water sampling bottles" used by oceanographers to obtain subsurface samples of seawater to determine the properties of sea-water. These bottles are generally metal or plastic tubes with either plug valves at each end. The bottle is lowered by wire with its valves open at both ends to the desired depth. It is then closed in situ by allowing a weight (called a messenger) to slide down the wire and strike the reversing mechanism. This causes the bottle to turn upside down, closing the valves and reversing the reversing thermometers, which are mounted on the bottle in a special thermometer case. If, as is usually the case, a series of bottles are lowered, then the reversal of each bottle releases another messenger to actuate the bottle beneath it. Generally a number of bottles (12 to 24) are attached at predetermined intervals in series along the wire (a 'bottle cast') and closed in succession. When the bottles have been brought back to the deck the water samples are drawn through a tap, following a routine designed to obtain a pure sample. In some designs, the bottle when tripped is released at its upper end and rotates through 180 degrees about a hinge at its lower end where it is clamped to the wire. This is for the purpose of operating the 'reversing thermometers' and leads to the bottles being referred to as 'reversing bottles'. In other designs, the bottle remains stationary while a frame carrying the reversing thermometers rotates. A capacity of 1.25 liters is common for these bottles but for special purposes, such as carbon-14 analysis, larger bottles are used - up to several hundred liters capacity. Another arrangement of water bottles is in the form of a so- called 'rosette sampler'. In this, 12 to 20 water bottles are mounted in a single frame which is attached to the end of the oceanographic wire. This has an electrical conductor incorporated; the bottles can be closed when desired on electrical command from the deck. This rosette arrange…

Bottles/Flasks/Jars
type: Concept