Atmosphere volumetric analysis

At 14.7 psia and 32°F, 1 mol of any gas occupies 359 ft3. The volume per pound of any gas at these conditions can be found by dividing 359 by the molecular weight of the gas and correcting for the gas temperature by multiplying the volume by the ratio of the absolute flue-gas temperature and the atmospheric temperature. To change the weight analysis (step 3) of the products of combustion to volumetric analysis, set up the calculation thus ... 

The sensitivitiea of classic analytical methods, particularly gravimetric and volumetric analysis are insufficient in the analytical chemistry of the atmosphere. Furthermore, in most cases, it is impossible to accumulate sufficiently large amounts of the sample, which would make it possible to use... 

The analysis of dry atmospheric air varies with location, altitude, time of year, and other factors. Table 4.4 gives the molecular weights of the constituents and the volumetric and gravimetric analyses. 

ORSAT ANALYZER - A furnace atmosphere analysis device in which gases are absorbed selectively (volumetric basis) by passing them through a series of pre-selected solvents. 

It may be tempting to increase the loop volume to increase the amount of sample for trace analysis. Before this is done, the system should be examined. If g-in.-diameter columns are used, a reasonable flowrate is 30 mL/min at atmospheric pressure. But if the pressure at the head of the column is at 3 atm (300 kPa) (which is not unreasonable), the volumetric flow at the head and through the sample loop is only 10 mL/min, or 6 s/mL. If the loop volume is increased to 5 mL, it will take 30 s to sweep the sample onto the column. Thus no peak can be any narrower than 30 s. A large-volume loop can completely destroy the separating efficiency of the chromatographic process. Again, as with any analytical problem, a common sense, logical examination of the whole picture will pinpoint problem areas. 

Note 17—Should the blank reading exceed 0.020, the precision obtainable will be impaired. If so, make an analysis of the reagents alone to determine whether the atmosphere or reagents are at fault. Place 30 mL of the HjOj (1.5 %) in the 50-mL volumetric flask, dilute to the mark with HCl (1+215), and proceed as described in 14.6. If this reagent blank reading exceeds 0.010, results should not be considered reliable. 

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