Calcium gravimetric analysis

We can solve the city s problem by doing some careful gravimetric analysis, because calcium salts and carbonate compounds undergo double-displacement reactions to 3deld insoluble calcium carbonate as a precipitate. 

A At Harvard 1 took a course on quantitative analysis for which we had to do the gravimetric analysis of calcium in limestone. But the instructor told us that we were wasting our time any sensible person would use atomic spectroscopy. I asked what it was and he told me to read a small book written by Gerhard Herzberg, who would later win a Nobel Prize for spectroscopy. 1 did, and that summer at home I made my own carbon arc for taking atomic spectra of various compounds. 

Microwave laboratory ovens are currently quite popular. Where applicable, these greatly shorten drying cycles. For example, slurry samples that require 12 to 16 hours for drying in a conventional oven are reported to be dried within 5 to 6 minutes in a microwave oven. The time needed to dry silver chloride, calcium oxalate, and barium sulfate precipitates for gravimetric analysis is also shortened significantly. ... 

Although preliminary separations may be required, in other instances the precipitation step in gravimetric analysis is sufficiently selective that other separations are not required. The pH is important because it often influences both the solubility of the analytical precipitate and the possibility of interferences from other substances. For example, calcium oxalate is insoluble in basic medium, but at low pH the oxalate ion combines with the hydrogen ions to form a weak acid. 8-Hydroxy-quinoline (oxine) can be used to precipitate a large number of elements, but by controlling pH, we can precipitate elements selectively. Aluminum ion can be precipitated at pH 4, but the concentration of the anion form of oxine is too low at this pH to precipitate magnesium ion. 

Quantitation provides the highest accuracy level achievable by CaCOs methods. The digestion of calcium carbonate can be determined in four different ways (1) digestion with acid (2) thermal gravimetric analysis (TGA at 105°C, 450°C, 550°C, and 1000°C... 

In gravimetric analysis, the solution-preparation step has its own special significance. The analyte must be separated from interfering species, or the interferents must be masked. For example, if iron(III) is to be estimated as its hydrated oxide in the presence of chromium(III), then the mixture is initially treated with perchloric acid so as to oxidize chromium(III) to chromate (chromium(VI), Cr04 ), followed by addition of ammonia to precipitate the hydrated iron oxide. Sometimes it is necessary to remove interferents, for example, when calcium is to be estimated as calcium sulfate in the presence of barium. The barium is removed as its chromate and the calcium is precipitated quantitatively as its sulfate. 

TG has been applied extensively to the study of analytical precipitates for gravimetric analysis [9]. One example is calcium oxalate, as illustrated in Figure 2. Information such as extent of hydration, appropriate drying conditions, stability ranges for intermediate products, and reaction mechanisms can all be deduced from appropriate TG curves. Figure 2 also includes the first derivative of the TG curve, termed the DTG cmve, which is capable of revealing fine details more clearly. 

An interesting kinetic study deals with the solution-mediated phase transformation of COT and COD into the thermodynamically stable COM [50]. The experimental conditions were adjusted so that either COT or mixtures of COD and COM crystallized initially as confirmed by X-ray diffraction powder patterns. The systems were then aged in contact with the mother liquid, and the transformation of COT or COD into COM was followed by monitoring the total crystal volume as a function of time (by Coulter counter) and determining (by thermo-gravimetric analysis) the relative proportion of the crystal hydrates at fixed time intervals. In addition, supersaturation profiles (i.e., activity products) were determined by solution calcium analysis. In all cases the transformation was completed within approximately 80-100 h. 

In Part Four, Chapter 11 offers the effectiveness of calcium carbonate nanoparticles on the improvements of compressive strength and durabUity of high-volume fly ash concrete. These resulting properties are further correlated with relevant microstructure and crystalline phases by means of X-ray diffraction, mercury intrusion porosimetry, differential thermal analysis, and thermal gravimetric analysis. Chapter 12 reviews current research and relevant techniques for the manufacture and application of amorphous carbon and its nanocomposites. Various applications for the textile, plastic, and healthcare industries, as well as in the fields of gas and water filtering, electrical apphcations, and food packaging, are also discussed based on the superior and unique propoties of... 

Analytical methods employed in soil chemistry include the standard quantitative methods for the analysis of gases, solutions, and solids, including colorimetric, titrimetric, gravimetric, and instrumental methods. The flame emission spectrophotometric method is widely employed for potassium, sodium, calcium, and magnesium barium, copper and other elements are determined in cation exchange studies. Occasionally arc and spark spectrographic methods are employed. 

A standard wet chemical analysis (ASTM D-811) is available for determination of aluminum, barium, calcium, magnesium, potassium, silicon, sodium, tin, and zinc. The procedure involves a series of chemical separations with specific elemental analysis performed by using appropriate gravimetric or volumetric analyses. 

Classical noninstrumental methods are used in routine analysis due to their easily accessible laboratory equipment required for implementation. In addition, they are often the official methods proposed by the corresponding government commissions. Acid-base titrations are used for ingredients that present acid-base properties (e.g., potassium and/or sodium hydroxides), iodometric titrations for the determination of oxidizing agents (e.g., hydrogen peroxide in hair-care products) even gravimetric determinations are carried out (e.g., oxalic acid and/or its alkaline salts by precipitation with calcium or zinc by 8-hydroxyquinoline). 

Precipitation. Sulfate can be precipitated by either the barium or calcium ion, and both are used commercially. Turning first to barium, we note that the solubility of BaS04 is so low that its precipitation is the standard gravimetric technique for analysis for the sulfate ion. In a brine loop, the precipitation step could be located anywhere, but it is most convenient to combine it with the precipitation of metals in the brine treatment tanks (Section 7.S.2.2) and not to add another step to the process. 

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