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Abstract

A method and apparatus for determining the moisture in materials is provided. The apparatus allows the accurate determination of moisture in a sample as small as 1 mg with a sensitivity of less than 1 microgram of moisture. The apparatus includes a vacuum chamber which can be cooled to below -150.degree. C. or heated to about 100.degree. C. The vacuum chamber is connected in series with a moisture trap which can be cooled to below -150.degree. C. The moisture trap is connected in series with a combination of mechanical and diffusion vacuum pumps capable of reducing the pressure in the apparatus to below 1.times.10.sup.-5 Torr. A sample is placed in the vacuum chamber, cooled to below -150.degree. C., the apparatus is evacuated to a pressure of below 1.times.10.sup.-5 Torr by the vacuum pumps. Thereafter, the moisture trap is cooled to below -150.degree. C. while the sample is heated to about 100.degree. C. to transfer moisture from the sample to the trap. When the transfer of moisture from the sample to the moisture trap is completed, as indicated by a stabilization of pressure with the apparatus, the moisture trap is isolated, heated and the change in pressure directly indicates the amount of moisture removed from the sample. Alternatively, the apparatus can include flow rate determining means oriented between the vacuum chamber and the moisture trap to determine the flow rate of moisture from the sample to the moisture trap for a given sample temperature.

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