Normal Standard Seawater (S = 35), accurately calibrated in conductivity ratio (K15) and in salinity.  This is the main single-point standard for salinity measurements.

The standards, which have a precisely known electrical conductivity ratio, are used for the calibration of salinity measurement devices.  For over 100 years, the comparability of salinity data worldwide has depended on the widespread use of this standard for calibrating laboratory and in-situ instruments.  

IAPSO Standard Seawater is available in high quality, crimp sealed glass bottles, each containing ca.200ml of natural seawater.  Each bottle's label carries information on its conductivity ratio (K15) and salinity according to the Practical Salinity Scale 1978 (PSS78).

The bottle is made from pharmaceutical-grade glass, which minimises any interactions with the seawater and thereby increases the shelf-life of the product.

The bottle’s narrow-neck is sealed with a halobutyl, polymer-coated bung, providing a totally impervious barrier to evaporation.  A secure, tamper-evident seal is made with a colour-coded alloy crimp-cap.