Abstract: A collapsible cup has a base and a series of cylindrical body segments that together form a rigid cup body. The base includes a cylindrical base segment extending upwardly from the base and having an external thread. The series of cylindrical body segments are of graduated diameters which telescopically engage each other and the cylindrical base segment, and include an externally threaded upper portion, and an internal thread that extends the across all of an internal surface of each of the cylindrical body segments, such that each of the cylindrical body segments is threadedly engaged with and supported by either the external thread of the cylindrical base segment, or the externally threaded upper portion of one of the cylindrical body segments.

Abstract: A pH sensor based upon spectrophotometric techniques has been developed for in situ analysis of an aqueous medium, e.g., surface seawater. This sensor utilizes a spectrophotometric pH indicator (Thymol Blue), which has been calibrated for use in seawater as a function of temperature and salinity. Shipboard spectrophotometric pH analyses routinely demonstrate a precision on the order of .+-.0.0004 pH units. In situ analysis of seawater pH has demonstrated a precision on the order of .+-.0.001 and an accuracy, using shipboard measurements as a standard, on the order of .+-.0.01. The sensor is a self-contained system that pumps seawater, meters in indicator, and spectrophotometrically determines indicator absorbance cells, each with three wavelength channels, to obtain the spectrophotometric absorbance. The sensor system, rated for depths up to 500 m, provides pH, conductivity, and temperature and can be operated via computer or in a standalone mode with internal data storage.