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";s:4:"text";s:30536:"The authors reported that when CA is heated it will dehydrate to yield the cyclic anhydride that reacts with starch; successively another cyclic anhydride function can be achieved into CA structure through the other two non-reacted carboxylic groups, allowing then the attachment of another hydroxylic starch group (Fig. Development of shellac-coated sustained release pellet formulations. We will also determine the citric acid concentration in a non-cola soft drink. P G JEFFERY, D HUTCHISON, in Chemical Methods of Rock Analysis (Third Edition), 1981. Thus, osteoporosis can be prevented by frequent uses of lemon in daily meals [65]. 0 0. But this cannot be calculated exactly, because citric acid is not the only acid in a lemon, although it is the most abundant. That is, and we can write: Solved problem. Coma et al. The use of co-formulated citric acid and low substituted hydroxypropyl-cellulose results in extremely fast dissolution of carbamazepine from solid dosage forms [19]. I'm not sure how to divide it up and I can't find it anywhere online :/ Source(s): dissociation citric acid: https://tr.im/SKXsS. I. It is formed in, TABLE 9.3. Citric acid is used in effervescing mixtures, and citric acid monohydrate is used in the preparation of effervescent granules. This article deals mostly with Brønsted acids rather than Lewis acids. 'mixed' acid dissociation constant appropriate to this ionic strength (pKA(MIX) = 6.85) a much lower pH of 7.15 is calculated. The salts of citric acid (citrates) can be used as anticoagulants due to their calcium chelating ability. It is used as an effective ingredient in an orally or parentally administrable agent for antiosteoporosis. On the influence of some inorganic salts on the partitioning of citric acid between water and organic solutions of tri-n-octylamine. Those values … Trehalose (86) is a disaccharide occurring in fungi, moulds, ergot, algae, yeast and insects. Thermodynamics and ion—solvent interactions of trichloroacetic acid in 50% dioxane—water. the Altmetric Attention Score and how the score is calculated. Nevertheless, the preference of Fe3+ for the citrate ion is only slightly greater than that for phosphate, and if the conditions change, casse can still occur. Citric acid is a weak triprotic carboxylic acid, i.e. By continuing you agree to the use of cookies. Considering that the pH of must and wine generally lies between 2.8 and 3.8, it can be assumed that the third dissociation does not occur. Electrochemical behavior of dopamine in the presence of citrate: Reaction mechanism. In biochemistry, it is important as an intermediate in the citric acid cycle and therefore occurs in the metabolism of almost all living things. Based on these considerations, citric acid is stronger than malic, but, normally it presents a quite low concentration in wine: in young wines, prior to malolactic fermentation, citric acid amount ranges from 0.5 to 1 g/L ( Ribéreau-Gayon et al., … This is “Appendix C: Dissociation Constants and pKa Values for Acids at 25°C”, appendix 3 from the book Principles of General Chemistry (v. 1.0). European Journal of Pharmaceutical Sciences. Citric acid is classified as a weak organic acid because it partially dissociates, or separates, when dissolved in a solvent, particularly water. 2.5. Proposed molecular structure for 2:2:4 Fe:U:citric acid complex, which is recalcitrant to biodegradation (Dodge and Francis 2003). It's not a matter of how many hydrogen are still attached IN THE EQUATION, but rather … Dissociation constants of carboxymethyloxysuccinic acid. An example, using ammonia as the base, is H2O + NH3 ⇄ OH− + NH4+. Standard cobalt stock solution, dissolve 0.807 g of cobaltous chloride hexahydrate in water containing 2 ml of concentrated hydrochloric acid and dilute to volume in a 1 litre volumetric flask. It also increases trabecular bone volume in healthy rats, and protects against the loss of bone during experimental osteoporosis. Please Help! The protective effect of citric acid against ferric casse is based on the formation of complexes with Fe3+; these complexes are yellow and have a composition that has not been fully elucidated. Although the first dissociation constant of citric acid has been found by conductivity to be 8.2 x 10e4 by Walden,’ and 8.0 x 10m4 by Walker* at 25’, and by pH determinations 7.9 x 10m4 by Enklaar3 at 18”, the values of the second and third dissociation constants have not been available. For details on it (including licensing), click here. The physiologic effect of anhydrous citric acid is by means of Decreased Coagulation Factor Activity. It is a tricarboxylic acid with the chemical formula C 6 H 8 O 7.The common way of representing the chemical formula of citric acid is C 3 H 5 O(COOH) 3.This indicates that citric acid has three carboxylic acid groups (-COOH). Citric acid has also been used in preparations for the treatment of gastrointestinal disturbances and chronic metabolic acidosis caused by chronic renal insufficiency or syndrome of renal tubular acidosis [1,2,4–6,20,21,79]. Acid-base equilibria in ternary water/methanol/dioxane solvent systems. Citric acid occurs in the terminal oxidative metabolic system of all but a very few organisms. Über die Autor*innen. What is the dissociation equation for boric acid. A.J. However, in the presence of excess citric acid, after biodegradation of excess citrate, the 1:1:2 complex transformed to a 1:1:1 Fe-U-citrate species (Dodge and Francis 1997). L. Ambrosio, ... A. Sannino, in Biomedical Hydrogels, 2011. – Citric acid pKa (8) Temp. Anhydrous citric acid is a Calculi Dissolution Agent and Anti-coagulant. CA and its salts, with a good affinity for metal ions, are used in a wide variety of applications: in soft drinks and effervescent salts, as an antioxidant in food, as a sequestering agent for metal ions, as a cleaning and polishing agent for metals, as a mordant in dyeing. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry. It is reported that the global citric acid demand is somewhere between 950,000 and 975,000 metric tons per year. (2006), for example, studied the optimum conditions for corn starch and CA reaction to produce resistant starch and studied the thermal stability of citrate starch products. Nitroso-R-salt solution, dissolve 0.05 g of the reagent in 100 ml of water. Distribution of Alkali Metal Picrates between Water and Methyl Isobutyl Ketone. Double layer studies of aqueous sodium citrate solution at the mercury electrode. Citric acid chelates calcium and is used by blood banks, since the citrate-calcium chelate helps to prevent blood coagulation. 2.5). The effect of citric acid in lemon (Citrus sp. Citric acid is used in beverages, jellies, jams, preserves, and candy to provide tartness, acid taste. The first dissociation constant of citric acid is similar to that of tartaric acid; the second constant is half that of tartaric acid but three times greater than that of malic acid. The Enzyme-Free Cell Dissociation Solution is a Hank′s based formulation of chelating agents & agents to stabilize their activity on cells. They additionally found that excessive citric acid tended to increase the surface roughness. Dissociation quotients for citric acid in aqueous sodium chloride media to 150°C. Ionization Constants by Curve Fitting: Determination of Partition and Distribution Coefficients of Acids and Bases and Their Ions. These results suggest that Fe-U-mixed-metal citric acid complexes resist biodegradation and may persist in the environment. Hagers Handbuch der Pharmazeutischen Praxis. Use of a citric acid aerosol spray has been reported as a safe, convenient, and efficacious smoking cessation aid. Citric acid monohydrate is used as a synergist to enhance the effectiveness of antioxidants [1,2,4,6]. Physical and Chemical Properties of l-Malic Acid. Older formulations would have written the left-hand side of the equation as ammonium hydroxide, NH4OH, but it is not now believed … Dissociation of Citric Acid? Xie et al. Nagoba et al reported an effective and economical approach for the treatment of superficial pseudomonas infections with citric acid [23]. it has three protons available for dissociation. Se Gas and Cd It is an acid compound found in citrus fruits. Its concentration in … The citric acid industry is highly concentrated and very competitive. Citric acid has three ionisable carboxylic acid groups. Potassium citrate, which does not have the same effects on flavor as citric acid, can be used since the process depends on the citrate anion. The three Ka values are: 7.1 × 10 -4; 1.7 × 10 -5, 6.4 × 10 -6 (CRC Handbook). This is for our Science Research Project, and we cannot find anywhere on the internet that shows how the dissociation of acetic and citric acid is endothermic or exothermic. It is used in the manufacture of alkyd resins, in its esterified form as a plasticizer and foam inhibitor, in manufacture of citric acid salts, an aid to facilitate abscission of fruit in harvesting, and in cultured dairy products. The coordination of the metal to citric acid affects the biodegradation of the metal-citrate complexes. Calculation by computer of individual concentrations in a simulated milk salt solution. Calculation of neutralization enthalpies from thermometric titrations of diprotic and triprotic acids using a linear least-squares method. The acidic environment also creates a barrier to the entry of bacteria and their colonization in … 1970; Binder 1971; Markovits et al. Problem (1): What is K b for the equilibrium: Solution: In the table blow this subject, K a value of 6.2 × 10-10 for HCN. It is widely used to add an acidic (sour) taste to soft drinks, jams, candies, and so on. The second value of α for citric acid, however, will be very to close to acetic acid's, because the second dissociation has aproximately the same ${pK_a}$ (4.76)$^1$. 2 The … Calorimetric determination of linkage effects involving an acyl-enzyme intermediate. Get … Citric acid is a weak acid most commonly found in citrus fruits. 0 0. It would be most effective for preparation of a buffer with a pH of It would be most effective for preparation of a … The first dissociation constant of citric acid is similar to that of tartaric acid; the second constant is half that of tartaric acid but three times greater than that of malic acid. This is demonstrated in Table 7.6. 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Bulletin of the Chemical Society of Japan. Nuclear magnetic resonance investigation of the interaction of water vapor with sildenafil citrate in the solid state. Table 7.6. In practice, this treatment is only used in white wines. They dissociate in water to produce a Lewis acid, H +, but at the same time also yield an equal amount of a Lewis base (acetate, citrate, or oxalate, respectively, for the acids mentioned). Part I. Potentiometric and calorimetric investigation of H+ and Na+ complexes with citrate, tartrate and malate. Journal of Natural Resources and Life Sciences Education. What is the dissociation enthaly of acetic and citric acid? Dorene. Unless otherwise stated, values are for 25 o C and for zero ionic strength. Rakesh Maurya, ... Prem P. Yadav, in Studies in Natural Products Chemistry, 2008. Like glycine, citric acid has a synergistic effect when added to a slurry that already contains hydrogen peroxide [54]. In the following acidification with hydrochloric or citric acid, the re-formation of casein particles was observed. When measured at 25°C and an ionic strength of 0.1, the pKa values are pK1 = 4.71 and pK2 = 3.24 [7]. Citric acid is a commodity chemical produced and consumed throughout the world. TABLE 9.4. A comparative study of void volume markers in immobilized-artificial-membrane and reversed-phase liquid chromatography. This is thought to be due to slow desorption of the Cu–citrate complex from the copper surface. Citric acid is a weak triprotic carboxylic acid, i.e. Like glycine, the addition of citric acid expands the dissolution and solubility ranges on the Pourbaix diagram while reducing the passivity region, as shown in Figure 7.43 for citric acid and dissolved copper with a total activity of 10−4. Method of analysis of data from measurements of heat of dissolution for some dicarboxylic acids at 298.15K. Synergistic Effect of Citric Acid and Hydrogen Peroxide. Because citric acid is a dry powder, its use allows for formulation of dry dialysates, which offer convenience for transportation and storage [79]. Rutaceae) juice was studied on osteoporosis. Further reaction with a cellulose hydroxyl of another chain can then lead to crosslinking. Instead, we find the acid dissociation constant for the conjugate acid, ammonium ion. Store in a refrigerator. Copyright © 2021 Elsevier B.V. or its licensors or contributors. Triprotic acids, such as phosphoric acid (H 3 PO 4) and citric acid (C 6 H 8 O 7), have three. 6.5. A combination of citric acid and glycine was used to improve the dissolution stability of hard gelatin capsules by preventing pellicle formation or cross-linking of the capsule gelatin [18]. Citric acid is a tri-carboxylic acid. Find more information about Crossref citation counts. Therefore, for all practical purposes, citric acid acts as a diprotic … The formation of proton and alkali-metal complexes with ligands of biological interest in aqueous solution. Void volume markers in reversed-phase and biomimetic liquid chromatography. The dose of citric acid ranges from 20 to 30 g/hL and treatment to prevent ferric casse is complemented by addition of gum arabic, which acts as a protective colloid to inhibit the flocculation of colloidal ferric phosphate. Citric acid can be substituted for acetic acid as the acidifying agent in dialysates. Thermodynamics of proton dissociations from aqueous citric acid: apparent molar volumes and apparent molar heat capacities of citric acid and its sodium salts at the pressure 0.35 MPa and at temperatures from 278.15 K to 393.15 K. THE SOLUBILITY OF CALCIUM CITRATE HYDRATE IN SODIUM PERCHLORATE SOLUTIONS. Trehalose acts by inhibiting the differentiation of osteoclasts, thus, inhibiting bone resorption [66]. Calculation of reference pH values for standard solutions from the corresponding acid dissociation constants. Acidified diets with 1% citric acid and 0.7% fumaric acid showed drop in stomach pH from 4.6 to 3.5 and 4.6 to 4.2, respectively, in weaned piglets (Sciopioni, Zaghini, & Biavati, 1978). Biotransformation of the ternary 1:1:2 Fe:U:citric acid complex by P. fluorescens showed that it was recalcitrant. of ≥ 4. A specific effect of citric acid treatment on isolated cell nuclei from bovine cerebral cortex results in extraction of a specific set of proteins from the nuclei rather than separation of inner and outer nuclear membranes [17]. 9.5H2O. The xylooligosaccharides contain ≤ 50 wt % xylobiose (88) and ≥ 40 of xylooligosaccharides having a d.p. Citric acid has three carboxyl and one hydroxyl group. Cryoscopic studies in the citric acid — water system. Thermodynamic interactions of the alkaline earth metal ions with citric acid. (1995) the two main stages of the reaction of polyfunctional carboxylic acids with cellulose are firstly due to the attachment of the polyfunctional carboxylic acids via esterification with a cellulosic hydroxyl group and its further reaction – via esterification – with another cellulosic hydroxyl group producing a crosslink between cellulose chains. Organic Brønsted acids, such as acetic, citric, or oxalic acid, are not Lewis acids. Citric acid is classified as a weak organic acid because it partially dissociates, or separates, when dissolved in a solvent, particularly water. Mathematical representations of citric acid dissociation, in electrolyte solutions and in buffers are discussed. By taking advantage of the buffer action of citric acid, sodium citrate is used in seasonings, and as a pH controller and emulsifier for processed cheese. Lv 4. In Great Britain, citric acid (1 in 500 parts of water) is an approved disinfectant for foot and mouth disease [1]. Synthesis of CdSe Nanocrystals through a Reaction of H This mechanism is based on an anhydride intermediate formation. Citric acid has an acid dissociation constant of 8.4 × 10 −4. Approximately two-thirds of the citric acid produced is consumed in the food and beverage industry, primarily as an acidulant [24–26]. Mathematical representations of citric acid dissociation, in electrolyte solutions and in buffers are discussed. Citric Acid - Its Natural and Synthetic Derivatives. The strength of an acid is measured not necessarily in terms of pH but on its dissociation in a solvent. Thermophysical Properties Research Literature Retrieval Guide 1900–1980. The degree of dissociation of citric acid's first dissociation $\ce{C6H8O7 <=> C6H7O7- + H+}$ is greater than acetic acid's, because it's ${pK_a}$ is smaller (3.13 vs 4.76)$^1$, meaning it's a stronger acid. Its experimental pH is around 2-3. Diffusion in buffered protein solutions: combined Nernst–Planck and multicomponent Fick equations. Citric acid has three relatively similar dissociation constants, thus instead of giving three (or at least two) separate end points, it has a long ramp, at which buffering effect of the first and … Direct infusion of a citrate solution, which was prepared from ten grams of citrate powder (2.0 g of citric acid, 4.0 g of monopotassium citrate, and 4.0 g of monosodium citrate) in 100 mL of distilled water, into the pancreatic ducts dissolved calcifications in two women with chronic abdominal pain caused by pancreatic duct obstruction [79]. Dissociation Constants for Citric Acid in NaCl and KCl Solutions and their Mixtures at 25 °C. This solution contains 200 μg cobalt per ml. Citric acid (85) is present in many citrus plants. Reviewers, Librarians Journal of Thermal Analysis and Calorimetry. Dietary xylitol (87) supplementation increased bone Ca and phosphorous in healthy rats, as well as protected against the decrease of bone minerals and bone density during experimental osteoporosis. Citric acid is thought to react with copper first by adsorption of the citrate ions onto the copper surface, followed by reaction and then desorption of the newly formed complex. It is also used as a natural preservative. Standard cobalt working solution, dilute 5 ml of this stock solution to 1 litre with water. It also serves as an environmentally benign cleaning agent and acts as an antioxidant. Lemonade therapy was effective in elevating urine citrate levels in 12 patients with hypocitraturic calcium nephrolithiasis. Plenum Press: New York, 1976. Dissociation constants of 2.79, 4.30 and 5.65 are reported in secondary literature (EFDB). Kenneth C. Cadien, Lucy Nolan, in Handbook of Thin Film Deposition (Third Edition), 2012. Citric acid (CA) is widely used in the food and drug industry and is an excellent candidate as a crosslinking agent. Citric acid solution, 0.20 M solution, dissolve 4.2 g of the purified reagent (monohydrate) in water and dilute to 100 ml. 2+ Figure 7.43. It can be seen from this diagram that citric acid is only able to form complexes with the Cu2+ form of ion, not Cu+. It was found that it increases Ca absorption through its chelating effect. Citric acid powder is sold for home use with no restrictions. Its concentration in citrus fruits varies depending on the species. Thus, Hydronium Ion Concentration of Solutions of Weak Acids When the weak acid HA is dissolved in water, two … in °C 1) 3.14 20 2) 4.77 20 3) 6.39 20 •P r i n c i p l e o f t h e t e s t m e t h o d The chemical process described is generally only slightly temperature dependent in the environmentally relevant temperature range. 1972; Manzurola et al. It must be a rare that such calculations are useful however. The lemonade treatment resulted in good patient compliance, and was well tolerated and inexpensive. I need the equation for the dissociation of citric acid, H3C6H5O7. This solution contains 1 μg cobalt per ml. In the past it was used as an acidifying agent, and although it is still used in certain food products, its use is severely limited by the fact that it is easily degraded by many microorganisms, including lactic acid bacteria. Citric acid chemistry - syntheses of citric acid, neutralization, degradation, oxidation, esterification, formation of anhydrides, amides and citrate-based siderophores is reviewed. All values are from Martell, A. E.; Smith, R. M. Critical Stability Constants, Vols. The cycle also provides the carbonaceous materials from which amino acids and fats are synthesized by the cell [6,12–14]. Effect of citrate impurities on the reference pH value of potassium dihydrogen buffer solution. Citric acid forms mixed-metal complexes with various metal ions (Adin et al. Although the first dissociation constant of citric acid has been found by conductivity to be 8.2 x 10e4 by Walden,’ and 8.0 x 10m4 by Walker* at 25’, and by pH determinations 7.9 x 10m4 by Enklaar3 at 18”, the values of the second and third dissociation constants have not … Recently, CA was used as crosslinking agent in various cellulose derivative systems (Glusker, 1980, Wang and Chen, 2005, Coma et al, 2003, Xie et al, 2006, Yang and Wang, 1998) and different mechanisms have been proposed in the literature to explain the crosslinking reaction of cellulose polymers with CA. The acid dissociation constants for phosphoric and citric acids are as follows: Phosphoric acid Citric acid K a1 7.11 x 10-3 7.44 x 10-4 K a2 6.32 x 10-8 1.73 x 10 5 K a3 7.10 x 10 Citric acid is an ingredient of citrated anticoagulant solutions; and also a reactive intermediate in chemical synthesis. Mathematical representations of citric acid dissociation, in electrolyte solutions and in buffers are discussed. What do you think of the answers? Buffer pH and pKa values as affected by added glycerol and sucrose. Citric acid is a sour principle of citrus fruits such as orange and lemon and exhibits a mild and refreshing sour taste. As would be expected, the ionization constants decrease when the ionic strength is raised to 1.0 (pK1 = 4.45 and pK2 = 3.11), and increase when the ionic strength is decreased to 0 (pK1 = 5.097 and pK2 = 3.459). & Account Managers, For 1989). Appendix: Selected Acid Dissociation … Thanks Some researchers have noted that citric acid can produce an inhibitive effect, similar to that of BTA, under some circumstances [51]. The formation of the ternary 1:1:2 Fe-U-citrate complex involving the hydroxyl group of citric acid was established by a combination of analytical techniques including potentiometric titration, UV-vis spectrometry, gelfiltration chromatography, time-of-flight secondary ion mass spectroscopy (TOF-SIMS), and extended X-ray absorption fine structure (EXAFS) analysis (Dodge and Francis 2003; Fig. From: Comprehensive Membrane Science and Engineering, 2010, Hadi Poerwono, ... Harry G. Brittain, in Analytical Profiles of Drug Substances and Excipients, 2001. Name Formula K a1 pK a1 K a2 pK a2 K a3 pK a3 K a4 pK a4; Acetic acid: CH 3 CO 2 H: 1.75 × 10 −5: 4.756-----Arsenic acid: H 3 AsO 4: 5.5 × 10 −3: 2.26: 1.7 × 10 −7: 6.76: 5.1 × 10 −12: 11.29--Benzoic acid: C 6 H 5 CO 2 H: 6.25 × 10 −5: 4.204-----Boric acid Citric acid is a moderately strong organic acid. Global capacity in 1998 was almost 2 billion pounds (880 thousand metric tons). In 1999, five producing companies accounted for 65% of the world’s total citric acid capacity, and nearly 90% of the world’s refined and purified citric acid capacity [24]. In this study, skim milk powder dispersions were alkalized to pH 10.0 or 11.0, corresponding to reduced particle mass. Dissociation equation for boric acid? Lemon juice has a citric acid concentration around 50 g/L, that is around 0,25 molar. The titration curve for sodium citrate with HCl (Figure 1B) confirmed the observation that citric acid has no buffering capacity … We use cookies to help provide and enhance our service and tailor content and ads. It is normally found at higher concentrations in white wines, because in red wines it is transformed by malolactic bacteria. produced by the fermentation of sugars (> 1 M tonne per year) for use in beverages and foods (70%); Write the dissociations of citric acid (C6H8O7) according to the Arrhenius definition and according to the Bronsted Lowry definition. Casein micelles in milk cause turbidity and have poor stability at acidic conditions. This treatment is therefore not recommended for wines with an iron concentration that exceeds 15 mg/L, as these have a strong tendency to undergo ferric casse. Ions in Aqueous Medium and Their Optical and Structural Properties. The pH of 0.033 M citric acid is about 2.2, which is slightly higher than that of lemon juice.4 The 0.1 M sodium hydroxide and the phenolphthalein indicator are more hazardous. And all this is just for a monobasic acid; with citric when you get much below 10-4 M its second dissociation is significant (you could use your original formula though with the second pK a because then the first dissociation is approximately 100%.) This is because the values of the three dissociation constants are too close to permit distinction of the three proton receptor phases. The equation for the dissociation of acetic acid, for example, is CH3CO2H + H2O ⇄ CH3CO2− + H3O+. Capacity utilization in two largest producing regions was 88% by the United States and 85% by Western Europe. 0.1 to 10 weight parts of xylooligosaccharides are added to the 100 weight parts of health pet food. 1A). Physical and Chemical Properties of Citric Acid. Distribution of binary mixtures of citric, acetic and oxalic acid between water and organic solutions of tri-n-octylamine. The addition of citric acid is not recommended without a sufficient concentration of sulfite to guarantee microbiological stability. It has been used in electroplating, in special inks, in analytical chemistry for determining citrate-soluble P2O5, and as reagent for albumin, mucin, glucose, and bile pigments [2,4–6]. This is surprising as buffer solutions are nearly always at ionic strengths above that at which dilute solution … Alles zeigen . Citrate was found to be preferable to heparin as an anticoagulant during hemodialysis with cellulose triacetate dialyzers. Citric acid is well known as a disinfecting agent used for dialysis equipment. (Myrtaceae) containing broad leaves. The same workers found that the addition of small amounts of citric acid resulted in a very low surface roughness when polishing with abrasives and hydrogen peroxide, compared to using slurry of abrasives and hydrogen peroxide alone. According to Zhou et al. Attachment of the carboxylic acid moiety to cellulose’s hydroxyl group via esterification reaction of the first cyclic anhydride would expose a new carboxylic acid unit in citric acid, which has the proper chemical connectivity to form a new intramolecular anhydride moiety with the adjacent carboxylic acid unit. ";s:7:"keyword";s:24:"citric acid dissociation";s:5:"links";s:712:"Find The Button Seeds For Minecraft Ps4, Wwe Wrestlers Real Height, Faith Name Popularity, Indiana Deer Density Map, Oil Temp Before Driving, Ncis: New Orleans'' You'll Do Cast, ";s:7:"expired";i:-1;}