water, contrary to loss on drying, which detects any volatile substances. Techniques used for natural gas Natural gas poses a unique problem in terms of moisture content analysis because it can contain very high levels of solid and liquid contaminants, as well as corrosives in varying concentrations. Measurements of moisture in natural gas are typically performed with one of the following techniques: color indicator tubes chilled mirrors chilled mirror combined with spectroscopy electrolytic piezoelectric sorption, also known as quartz crystal microbalance aluminum oxide and silicon oxide spectroscopy. Other moisture measurement techniques exist but are not used in natural gas applications for various reasons. For example, the gravimetric hygrometer and the “two-pressure” system used by the National Bureau of Standards are precise, but are not suitable for use in industrial applications. Color indicator tubes The color indicator tube (also referred to as the Draeger Tube or Stain Tube) is a device that natural gas pipelines use for a quick and rough measurement of moisture. Each tube contains chemicals that react to a specific compound to form a stain or color when passed through the gas. The tubes are used once and then discarded. A manufacturer calibrates the tubes, but since the measurement is directly related to exposure time, the flow rate, and the extractive technique, it is susceptible to error. In practice, the error can reach up to 25 percent. The color indicator tubes are well suited for infrequent, rough estimations of moisture in natural gas. Chilled mirrors This type of device is considered the most popular when it comes to measuring the dew point of water in gaseous media. In this type of device, when gas flows across a reflective cooling surface, the eponymous chilled mirror. When the surface is cold enough, the available moisture will start to condense onto it in tiny droplets. The exact temperature at which this condensation first occurs is registered, and the mirror is slowly heated until the condensed water begins to evaporate. This temperature is also registered and the average of the condensation and evaporation temperatures is reported as the dew point. All chilled-mirror devices, both manual and automatic, are based on this same basic method. It is necessary to measure temperatures of both the condensation and evaporation, because the dew point is the equilibrium temperature at which water both condense and evaporate at the same rate. When cooling the mirror, the temperature keeps