The U.S. government is closed. This site will not be updated; however, NOAA websites and social media channels necessary to protect lives and property will be maintained.

To learn more, visit commerce.gov.

For the latest forecasts and critical weather information, visit weather.gov.

CCl4 Scale

Updated: January, 2008
Seven standards now comprise the GML CCl4 scale. Four standards prepared in 1996 were
removed from the scale due to inconsistent performance.
The 2008 scale is 0.4% lower than the 1996 scale based on ECD results.
Standard Prepared Assigned Difference
(ppt) (ppt) (ppt)
SX-3519 49.8 49.02 -0.76
SX-3518 25.4 26.18 0.78
SX-3522 41.5 41.21 -0.29
SX-3506 94.3 94.91 0.64
SX-3505 47.3 46.97 -0.30
ALM-33800 127.71 127.93 0.22
ALM-65990 153.09 152.80 -0.29
std dev 0.57
ccl4 scale tree