Alkalinity, measurement

When silica levels increase, hydroxide alkalinity measurements become increasingly important to ensure maximum silica solubilization and the reduction of risk of silica deposition. This is especially so for coil boilers because, more than any other boiler type, the use of hydroxide is critical in keeping the waterside surface of the coiled tube clean and deposit free. 

Logarithmic scale for expressing acidity or alkalinity of water (7.0 to 0 indicates increasing acidity 7.0 to 14 indicates increasing alkalinity). Measured by means of a glass electrode/reference electrode pair immersed in the water sample under test. The potential difference depends upon the pH which is then displayed on a pH meter (high input impedance, millivoltmeter). 

Alkalinity measurement is also required for the determination of active matter by difference and equivalent weight calculations. It can be determined as two of the following compounds sodium bicarbonate, sodium carbonate, or sodium hydroxide. The sample is titrated to a phenolphthalein endpoint to determine the sodium hydroxide/sodium carbonate content. An added measure of acid converts any bicarbonate to carbon dioxide, which is subsequently removed from the solution. Back-titration of the excess acid gives a measure of the amount of bicarbonate and/or carbonate present. 

A more rigorous method for interpreting an alkalinity measurement is to use a reaction model to reproduce the titration. The technique is to calculate the effects of adding acid to the original solution, assuming various carbonate contents. When we produce a model that reaches the endpoint pH after adding the acid, we have found the correct carbonate concentration. 

With these experimental surface reaction parameters and the speciation program MICROQL the species distribution in the river using metal and particle concentrations, pH and alkalinity measured in the river at the concerned sampling data was calculated. Various assumptions for the complexation in solution may be used, which affect ai and thus Kd-... 

Millero, F.J., A.G. Dickson, G. Eischeid, C. Goyet, P. Guenther, K.M. Johnson, K. Lee, D. Purkerson, D.L. Sabine, R.G. Schottle, D.R.W. Wallace, R.J. Wilke, and C.D. Winn. 1998. Total alkalinity measurements in the Indian Ocean during the WOCE hydro-graphic program C02 Cruises 1994-1996. Marine Chemistry 63(1-2) 9-20. 

Plastic 100 ml measuring cylinder (for alkalinity measurements, methods A and B)... 

Bicarbonate alkalinity. When P = 0, there is no OH- or C032- in the solution. The total alkalinity measured is all due to I IC()3. Thus, bicarbonate alkalinity = T. 

To further complicate matters in interpreting and using alkalinity measurements, apparent constants can only be used with data in which pH was measured and alkalinity calculated in exactly the same manner as that done for the samples. A classic example of the difficulties that can arise when these factors are not carefully dealt with is the GEOSECS carbonate data set (see Bradshaw et al., 1981, for discussion). Fortunately, for many open ocean water column studies of... 

Alkalinity has to be measured in the field because C02 is often pressurized in groundwater (due to addition of C02 from soil and other underground sources). Upon exposure to the atmosphere some C02 may leave the water, causing part of the HCO3 to break down. For these reasons it is highly recommended that alkalinity be determined in the field. Field-measured alkalinity values are needed for water-rock saturation calculations. Various setups are available for alkalinity measurements in the field by titration of the sample with an acid and pH coloring indicator. 

Neal, C., W. Alan House, and K. Down (1998). Assessment of excess carbon dioxide partial pressures in natural waters based on pH and alkalinity measurements. Science Total Environment. 210-211, 1-6, 173-185. 

An alternative method is to determine changes in total CO2 content of the sea water by monitoring pH, chlorinity, temperature and alkalinity (Park, 1969 Smith and Key, 1975 Smith and Kinsey, 1978) and to derive values for the flux of CO2 through the organic cycle, by subtracting from the total flux that component attributable to the inorganic carbonate flux as determined by alkalinity measurements. These estimates are relatively free from errors caused by diffusion, as CO2 exchange with the atmosphere is much slower than that of O2. However, the absolute precision of the measurement... 

It should be emphasized that the strength of the operational definition of pH is that it provides a coherent scale for the determination of acidity or alkalinity. Measured pH values cannot be expected to yield a detailed picture of solution composition that is entirely consistent with solution theory, however. This uncertainty stems from our fundamental inability to measure single-ion activities. That is, the operational definition of pH does not yield the exact pH as defined by the equation... 

Suppose now that we have a carbonate alkalinity measurement - either of an unpolluted fresh water, or a measurement corrected for the presence of other anions. This quantity (defined by Equation (3.57)) is obviously somehow related to the quantity we need, which is mcos,total (Equation (3.51)), but there are two problems ... 

We can also determine the contributing anions from pH and alkalinity measurements. Given that [OH-] = Kw[H+], the hydroxide alkalinity can be calculated from... 

The acidity of halogenated solvents can be determined by titration with 0.01N sodium hydroxide in the presence of a 0.1 % solution of bromophenyl blue indicator. Similar to the determination of alkalinity, acidity is determined in water extract. The determination can also be done directly in solvent but the solution of sodium hydroxide should be prepared in methanol. A third option is to determine acidity by a pH-metric titration of a water extract. Prior to determination, the pH of solvent is measured. If the pH is above 7, then an alkalinity measurement is done by the above method. If the pH is below 7, acidity is determined by this method. The method is used to establish purchasing and manufacturing specifications and control the quality of solvents. 

Alkalinity [HC03] + 2[C03-2] +[OH-]-[H+] Alkalinity measures the ability of a water to neutralize acid. 

Carbon dioxide Titrimetry, by calculation (from pH and alkalinity measurements)... 

Figure 4. Total alkalinity measured once at each of the five sampling sites in 2015 (single measurements).

DETERMINATION OF CARBONATE, BICARBONATE, AND FREE CARBON DIOXIDE FROM AND ALKALINITY MEASUREMENTS... 

Table VI. Factors for total alkalinity measurement. Factor / in the equation ...

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