1.1.3 Substandard Batches

Secondary lab-standard (substandard) seawater batches were used from the beginning of the HOT program in order to monitor drift of the Autosal within and between measurement sessions. Substandard batches were first used sometime around HOT-23 (February 1991). The seawater used for these batches was collected from 1000 m at Station ALOHA, stored in a glass carboy topped with mineral oil to prevent evaporation, and covered with a black plastic bag to prevent biological growth in the seawater. Appendix G is a record of Sean Kennan's calculations on how much mineral oil is needed for the glass carboy. A maintenance record on July 16, 1991 (Valenciano and Rii 2003, Autosal History Maintenance Database Report, Appendix H) suggests that air pumps on the Autosal 8400A malfunctioned possibly due to mercuric chloride, which had been put into the substandard batch along with mineral oil to inhibit biological growth. Use of mercuric chloride ceased starting batch #4 (December 1991). Details on substandard seawater batch use are discussed in Section 3.2.


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