RelativeResourceManager(6) - percent to ppm multiply by...

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6 of 17 3) Na 2 SO 4 formula wt. = 2(23) + 1(32) + 4(16) = 142 g/mole, charges involved = 2 equivalent wt. = 142 = 71 g/eq. 2 4) Al 2 (SO 4 ) 3 18H 2 O; formula wt. = 2(27) + 3(32) + 30(16) +36(1) = 666 g/mole, charges involved = 6 equivalent wt. = 666 = 111 g/eq. 6 (b) Examples of determination of milliequivalent weight. Using the examples from above, one milliequivalent of: 1) Na is 0.023g. or 23 mg/meq. 2) Ca is 0.020g. or 20 mg/meq. 3) Na 2 SO 4 is 0.071g. or 71.0, mg/meq. 4) Al 2 (SO 4 ) 3 • 18H 2 O is 0.111g. or 111 mg/meq. In each case, 6.02 x 10 23 ÷ 10 3 , or 6.02 x 10 20 positive or negative charges are supplied. C. Proportionalities Proportionalities are used throughout this course to describe concentrations of chemicals in soil or in solutions. Proportionalities do not have units, so when performing calculations with proportionalities the units do not change. Two common proportionalities are percent (%) and parts per million (ppm). Percent can be defined as parts per 100 parts. The ratio of ppm to percent is 1,000,000/100 or 10,000; therefore, to convert
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Unformatted text preview: percent to ppm, multiply by 10,000. We will commonly be dealing with ppm in our class in terms of milligrams per kilogram (mg/kg). When dealing with dilute solutions that have specific gravities close to that of water (1.0 g/ml), we can appropriately substitute 1 in for "kilogram" in the denominator since 1 kg of water = 1 l at 25°C. Another proportionality commonly used in this course is pounds per acre (lb/acre). Because an acre-furrow-slice (an acre 6 inches deep) is assumed to weigh 2,000,000 lbs., lbs/acre is the same as parts per 2 million. Therefore, to convert percent or ppm to lbs/acre, multiply by 20,000 or 2, respectively. Some comparative definitions: if 1% is then 1 ppm is (a) 1 lb. out of 100 lbs. 1 lb. out of 1,000,000 lbs. (b) 1 g. out of 100 g. 1 g. out of 1000 kilograms or 1,000,000 g. (c) 1 mg out of 0.1 g. 1 mg out of 1.0 kilogram (d) 1 mg in 0.1 ml 1 mg in a liter...
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