MCI Automatic Trace Metal Analyzer. Reliable, Fast and Easy.
Utilizes ASV method to simultaneously measure concentrations of 5 different trace heavy metals. Ultra-high sensitivity and automatic sample feed/discharge measuring cell assures fast, precise results. Reproducibility is 3-to-20%. Range: 0.1 PPB— 50PPM.
AS-01 Trace Metal Analyzer
MITSUBISHI CHEMICAL INDUSTRIES LIMITED Instruments Dept.. Mitsubishi Bldg., 5-2, Marunouchi 2-ohome, Chiyoda-ku, Tokyo, 100 Japan Telex: J 2 4 9 0 1 Cable Address: KASEICO TOKYO CIRCLE 140 ON READER SERVICE CARD
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RELIANCE GLASS WORKS, INC. 17 Gateway Road, Bensenville, IL 60106
(312) 766-1816
CIRCLE 183 ON READER SERVICE CARD
328 A · ANALYTICAL CHEMISTRY, VOL. 51, NO. 3, MARCH 1979
a counterweight, but the sphere was awkward to handle and too heavy for the microbalance. I then constructed a hollow, evacuated metal cylinder of stainless steel, light enough (17 g) to be weighed on a microbalance. Tracking the density of air with these devices as the temperature, barometric pressure, and humidity changed indicated that they give a density of air in agreement to better than 1 ppt with that calculated by Equation 3, not surprising inasmuch as they are calibrated using a density calculated by Equation 3. One part per thousand in the density of air is almost good enough to make to the correction for buoyancy to the 1 ppm level, but in 1975 a paper (78) published by P. E. Pontius of NBS stated that the formula for calculating the density of air is incorrect. Equation 3 is based on the ideal gas laws, and the Pontius claim posed a completely new problem. The problem stated more simply is: Does moist air conform to the gas laws? As a check on this, I constructed a hollow, evacuated cylinder of stainless steel with flat ends (Figure 1). The end pieces are sealed into thin-walled tubing of stainless steel by electron beam welding, and the cylinder is finished in a specially designed cylindrical lapping block of adjustable diameter. The volume of this "absolute density cylinder" was determined by precise measurement of the length and diameter with an optical comparator and gauge blocks. T h e mass (in vacuum) was determined by still another invention, a "vacuum weighing bottle" (Figure 2). The weighing bottle is closed by a cap which bears an O-ring and carries a stainless steel valve, the sealing element of which is again an O-ring. T h e empty weighing bottle is first evacuated and weighed, then opened and the cylinder (or counterweight, or weights) inserted; the bottle is then again evacuated and weighed. The buoyancy of air on the weighing bottle is the same in both operations so that the increase in weight is the mass ("true mass" or "weight in vacuum") (Note 4). Two counterpoises, equal in weight in air to the cylinder, are shown in Figure 1. These are useful in the refined measurements leading to a check on the validity of Equation 3 and useful when the cylinder is used in routine work. The hollow counterpoise has the same surface area as the hollow cylinder and is used in studies of surface effects. Work with these devices was first reported in the MS thesis of J. S. Gibson (Note 5), and work shortly to be reported will show that the density of air obtained by calculation from the temperature, barometric pressure, and relative humidity is reliable to 3-4
