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"PRECURSER UNIT
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106 A • ANALYTICAL CHEMISTRY, VOL. 43, NO. 6, MAY 1971
Precise moisture calibration standards from high-pressure gas cylinders have been developed. Key to the new sys tem is a device called a Precursor which operates in conjunction with spe cially prepared cylinder gas mixtures. A calibration standard with a mix range from 5 to 6000 ppm of water with an accuracy of ± 5 % of moisture can be delivered. Cylinder gases (any one or a combination of inert gases) used to prepare the mixtures contain less than 1 ppm of water (—105°F dew point). The Precursor fits in-line between the gas cylinder and use point. Outlet flow rate can range from 0.2 to 1 standard fts per hr. The system should be useful in laboratories for standardizing moisture detection equipment. The Precursor alone costs more than $250. Air Products and Chemicals, Inc. 215395-4911 505
NBS New Standards Twelve new standards have recently been made available by the National Bureau of Standards. They are: SRM 485, austenite in ferrite ; SRM 493, iron carbide in ferrite; SRM 720, synthetic sapphire; SRM 723, tris(hydroxymethyl) aminomethane (2 - amino -2 - hydroxymethyl-l,3-propanediol) ; SRM 917, D-glucose; SRM's 1206-2, 1207-1, 1207-2, 1208-1, and 1208-2, high-tem perature alloys; and two microanalysis standards: SRM 2141, urea; and SRM 2142, o-bromobenzoic acid. For a complete list of Standard Ref erence Materials, NBS Special Publica tion 260 is for sale by the Supt. of Documents, U. S. Government Printing Office, Washington, D. C. 20402, for 75
