Reasons for Performing Non – AqueousAcid – BaseTitration .................................................... 2
Interaction of H 2 O with the Titrant ...................... 2
Poor Solubility of Weak Acids (W A ) or Weak Bases (W B ) in H 2 O ........................................................... 3
The main objective of this experiment is to determine the amount of nicotine in commercial brand bidis and cigarettes by means of a non- aqueousacid-basetitration. This study focus on harmful level of nicotine present in bidis and cigarettes by comparative study of titration analysis with marketed tobacco powder.Nicotine is weak base so treatment with alkali strengthens it for acid-base reaction. Due to alkaloid in nature, nicotine was extracted out by highly organic solvent like toluene or diethyl ether etc. The liberated nicotine was titrated with perchloric acid using crystal violet indicator. Result shows that Marketed Tobacco powder and local bidis had more concentration of nicotine as compare to branded cigarettes.
Crystal violet is the frequently used indicator in non-aqueousacid-basetitration. However in the present titration, the end point was difficult to detect using crystal violet. The solution of LAN in dioxane was found to give pH of about 6. Among the indicators studied, crystal violet, bromophenol blue, bromocresol purple, neutral red, chlorophenol red and methyl red, only methyl red was found to give sharp end point because the pH range for color change of methyl red falls in the range of 4.2-6.3 (red-yellow). Although the approximate pH range for color change of chlorophenol red is 4.8-6.4 (yellow to orange), the detection of end point was difficult. Methyl red was found to dissolve easily in methanol, hence methyl red solution in methanol was used in the proposed titrimetric method.
dicators are presented in Table 2. It was observed that the natural indicator (waakye leaves extracts) when added to the acid produced a sharp yellow color as indi- cated in Table 1 and in Figure 1. For the strong acid the pH range was between 1.0 (acidic) to 12.0 (alkaline) after titration, whereas for the weak acid the pH was observed to be around 4.0 to 12.0 with exception in the case of a weak acid versus weak base as indicated in Table 1. The possible factors that might have contributed to the pattern of the pH variation as well as titre value could be tem- perature, ionic strength, colloidal particles and organic solvents . Another reason could be the chemical com- position of the natural indicators. Flavonoids and tannins have the capacity to produce sharp color changes at cer- tain pH ranges as compared to non-flavonoid and tannins derivatives because of the functional groups (e.g. OH) in flavonoids and tannins.
Potentiometric titration behaviour of a Tunisian glauconite complex natural clay mineral was investigated and interpreted according to surface complexation theory. Gran plots were used to determine the equivalence points of potentiometric titrations in solution and also the necessary parameters for the analysis of titration data. Proton surface charge can be calculated by subtracting supernatant titration curves from those of glauconite suspension. The surface complexation model (SCM) that fits satisfactorily our experimental data, is the double layer model (DLM) which was successfully capable to simulate the experimentally observed acid-basetitration properties of glauconite suspension. The optimisation procedure, using FITEQL program, was performed in two steps: first, the Fe and Si speciation was optimised with alkalimetric titration of supernatant solution, then; the optimised parameters were used in the alkalimetric titration of the glauconite suspension. Surface ionisation constants were then determined by FITEQL, the pKas values found are (pKa 1 =3.41,
Data providing proton adsorption on homoionic forms of sepiolite and paly- gorskite at I = 0.1 and I = 0.002 (titration points) are shown in Figure 2. How- ever, it should be noted that these potentiometric titration curves take account of dissolution processes involving structural Mg 2+ ions. Acid amount associated
Exactly 6 grams of dried petals of flowers (A. auriculiformis A. Cunn., C. juncea L. and S. javanica Miq.) mixed with 200 mL of deionized water were heated at 100 º C for one hour. The aqueous extracts were filtered by a filter paper, Whatman 1, and evaporated through a vacuum rotary evaporator at 60 º C. The extract indicators for study were prepared using 5 % (w/w) of dried extracts in water.
7.11 Potassium Hydroxide Solution, Standard Alco- holic (0.1 M)—Add 6 g of reagent grade potassium hydroxide (KOH) (Warning—Toxic and corrosive), to approximately 1 L of anhydrous isopropyl alcohol. Boil gently for 10 min to effect solution. Allow the solution to stand for 2 days and then filter the supernatant liquid through a fine sintered-glass funnel. Store the solution in a chemically resistant bottle. Dispense in a manner such that the solution is protected from atmospheric carbon dioxide (CO 2 ) by means of a guard tube containing soda lime or soda non-fibrous silicate absorbent (Ascarite, Carbosorb, or Indicarb), and such that it does not come into contact with cork, rubber, or saponifiable stopcock grease. Standardize frequently enough to detect normality changes of 0.0005 by potentiometric titration of weighed quantities of potassium acid phthalate dissolved in CO 2 -free water.
Hypokalemia is another characteristic complication of alkalemic disorders, more prominently those of meta- bolic origin. Shift into the cells at least partly account for the decline in extracellular potassium. The remainder of potassium deficit is attributable to renal and extrarenal losses [17, 67]. Hypokalemia can result in weakness, dysrhythmias, polyuria, and increased ammonia production. Other electrolyte abnormalities occurring during alkalemia can also result in severe complications commensurate to the severity of the particular electro- lyte derangement: hypocalcemia and hypomagnesemia can lead to tetany, seizures, and altered mental status. As mentioned previously in this chapter, alkalemia stimu- lates the generation of lactic acid and ketoacids through the induction of anaerobic glycolysis. Additionally, acute alkalemia shifts the oxygen–hemoglobin dissociation curve to the left, resulting in increased oxygen affinity of hemoglobin and consequent relative tissue hypoxia. This effect is eventually ameliorated in persistent alkalemic states by the induction of 2,3-diphosphoglyceric acid pro- duction in red cells.
Department of Biological Sciences, College of Science, University of Santo Tomas, Manila, Philippines
The organic compounds belonging to different functional groups have different properties affecting their chemical behavior. The experiment results are the following: cyclohexane and amyl acetate immiscible with HCl and NaOH; ethanol and ethylamine miscible with both reagents; phenol immiscible with HCl but miscible with NaOH, also does not form effervescence with NaHCO 3 ; and benzoic acid insoluble in HCl but soluble in NaOH, also form effervescence with NaHCO 3 .
Extract the original ether layer with about 1 mL of saturated aqueous sodium chloride solution and discard the aqueous layer (Organic Liquid Waste container in the hood). This removes most of the water dissolved in the ether. With a clean dry pipet, carefully transfer the ether solution to a clean dry vial, leaving behind any water clinging to the side of the tube. Use a few drops of fresh ether to do a transfer rinse. Drying is completed by adding anhydrous calcium chloride pellets in small numbers, with swirling, until the pellets no longer clump together. This vial should be capped and set aside.
The kinetics of oxidation of Schiff’s bases by TCICA in 100./. methanol has been investigated.The fractional order dependence of rate on [substrate] was confirmed by MIchaelis-Menton plot.The order with respect to acid is also found to be fractional. The activation parameters for variously substituted Schiff’s bases have been calculated by carrying out the reaction at various temperatures. A suitable mechanism has been proposed.
Acidity measurements of organic com- pounds, like those investigated here, are significant in studies that involve the formation and investi- gation of biological activities. An understanding of the acidity or basicity of organic compounds is fundamental to molecular design. The reaction me- chanisms are also very important for understanding the chemical and biological processes that may take place at the azometine site . It is well- known that acid-base properties affect the toxicity and pharmaceutical characteristics of organic acids and bases ; the biological activity of hydra- zones depends on the ionic forms in which they exist in solution .
completely. Weak acids reach equilibrium, where the fraction that has dissociated becomes a constant at a given temperature. For this reason, titrations are only used to find the equilibrium constants of weak acids. The numerical value of the equilibrium constant is unique to the acid and can be used to identify an unknown acid. Before the titration is begun, the initial pH of the solution is controlled by the auto-dissociation of the acid. At this point, the concentration of H 3 O + and A – are very small compared to the concentration of HA. When the basic
Viewed in this way, an acid is a proton source, a base is a proton sink. The tendency for a proton to move from source to sink depends on how far the proton can fall in energy, and this in turn depends on the energy difference between the source and the sink. This is entirely analogous to measuring the tendency of water to flow down from a high elevation to a lower one; this tendency (which is related to the amount of energy that can be extracted in the form of electrical work if the water flows through a power station at the bottom of the dam) will be directly proportional to the difference in elevation (difference in potential energy) between the source (top of the dam) and the sink (bottom of the dam).
The acidity of a chemical substance in water is dependent on which entity - water or the conjugate base of the acid - has a greater hold on the proton that’s responsible for the solution pH! It’s very a much a tug-of-war over one proton between two possible conjugate bases (remember water is the conjugate base of H 3 O + (aq)) as is outlined in the following simple illustrations: