OSIL Seawater Technical Notes | Environmental Instruments and Systems

Composition and most important chemical species of some dissolved elements in sea water.

Salinity is measured using the latest model of Guildline Autosal or Portasal salinometer. The manufacturer's quoted accuracy for the Guildline Autosal Model 8400B is 0.002 in salinity, although experience has shown that analysts can consistently obtain agreement of better than 0.001 in salinity. The salinometers, which are kept in optimum temperature controlled conditions, are standardised using IAPSO Standard Seawater at 35 salinity. The primary...

Standard seawater (SSW) has been employed by oceanographers as a reference material in the determination of salinity for over a century. In all that time, this is the first study to determine the uncertainty of the SSW manufacturing process. SSW is calibrated in reference to carefully prepared solutions of potassium chloride (KCl). All uncertainties in the preparation and measurement of KCl solutions and of new SSW are calculated. The expanded un...

IAPSO Standard Seawater is the only internationally recognised calibration standard for the measurement of Practical Salinity as approved by all the major oceanographic bodies (ICES, IOC Unesco, SCOR,etc) and is endorsed by the International Association for Physical Sciences of the Ocean (IAPSO).

Linearity Pack

Salinometer calibration for measurement of oceanic samples is traditionally carried out using IAPSO Standard Seawater (salinity = 35). For measurement of samples of higher and lower salinity, OSIL produce standards at salinities of 10, 30 and 38. Salinometer linearity checks provide a useful diagnostic tool in assessing the function of a salinometer and are routinely carried out at the OSIL Service Centre.

The procedure followed by OSIL when preparing and calibrating IAPSO Standard Seawater.

Stability of IAPSO Standard Seawater

A check of the calibration of 10 batches of International Association for the Physical Sciences of the Ocean standard seawater (P120-P129) against the defined KCl standard (practical salinity scale 1978) showed differences of less than 0.001 in salinity (equivalent to circa 0.00003 in K15) during storage periods of up to 96 weeks. An experimental batch stored in borosilicate bottles showed no significant difference from the seawater stored in gla...

Fundamental determinations of the physical properties of seawater have previously been made for Atlantic surface waters, referred to as ‘‘Standard Seawater’’. In this paper a Reference Composition consisting of the major components of Atlantic surface seawater is determined using these earlier analytical measurements. The stoichiometry of sea salt introduced here is thus based on the most accurate prior determination of the composition, adjusted ...

Using IAPSO Standard Seawater

OSIL's recommendations when using IAPSO Standard seawater particularly relating to storage, shelf-life and linearity.