Chloride with visual indication

Chloride is determined by titrating with Hg(N03)2, forming soluble HgCb-The sample is acidified to within the pH range of 2.3-3.8 where diphenylcarbazone, which forms a colored complex with excess Hg +, serves as the visual indicator. Xylene cyanol FF is added as a pH indicator to ensure that the pH is within the desired range. The initial solution is a greenish blue, and the titration is carried out to a purple end point. 

In variants based on the determination of alcoholyzable halogen, chlorine and bromine have been determined69 by solvolysing the sample in a sealed tube with sodium butoxide. The resulting chloride or bromide was determined by argentimetric titration, with visual, or preferably potentiometric, indication of the end-point. 

Gringras and Sjostedt273 reduced sulphonyl chlorides on paper chromatograms with a sodium sulphite reagent, then visualizing the sulphinate reaction product with tetrazot-ized o-dianisidine. Direct titrations of sulphonyl chlorides with sodium sulphide have also been performed, with instrumental or visual end-point indication (the latter depending on the formation of yellow polysulphide from the excess reagent and the sulphur produced)274-276. 

In a round bottom flask 16 ml of IN NaOH was added to 1 g of soybean/DEAD and heated using the thermowatch with heating mantel and flat surface thermocouple to 115°C, utilizing the reflux condenser. The reactions were heated while stirring for 24 h. Enough IN hydrochloric acid was added to the sample to acidify the solution to pH 6. There was also a visual indicator that acidity was reached because the reaction became cloudy and oil was formed noticeably. The sample was then transferred to a separatory funnel and 20 ml of chloroform was added to extract the product from solution. The chloroform layer was collected and washed two additional times with water and once with saturated sodium chloride solution. The chloroform layer was then dried with magnesium sulfate, filtered into a roimd bottom flask and evaporated in a rotatory evaporator. The product was then placed in the vacuum oven overnight at 50°C. 

The titration of ionizable chlorides with mercuric acetate solution in the presence of s-diphenylcarbazone as an indicator is used to determine chloride in trichlorotrifliioroethane. A visual appearance test to detect admixtures in halogenated solvents is based on the observation of suspended particles, sediment, turbidity and free floating water. 

The potentiometric detection of the endpoint of precipitation titrations is very often used because not many visual indicators are available, in particular when mixtures of analytes are titrated. Halides, cyanide, sulfide, chromate, mercaptans, and thiols can be titrated with silver nitrate, using the silver sulfide-based ISE. Also complex mixtures, such as sulfide, thiocyanide, and chloride ions, or chloride, bromide, and iodide ions, can be titrated potentio-metrically with silver(I) ions. When the solubility of a compound formed during titration is too high, nonaqueous or mixed solvents are used, for example,... 

In media selective for enterobacteria a surface-active agent is the main selector, whereas in staphylococcal medium sodium and lithium chlorides are the selectors staphylococci are tolerant of salt concentrations to around 7.5%. Mannitol salt, Baird-Parker (BP) and Vogel-Johnson (VJ) media are three examples of selective staphyloccocal media. Beside salt concentration the other principles are the use of a selective carbon source, mannitol or sodium pyruvate together with a buffer plus acid-base indicator for visualizing metabolic activity and, by inference, growth. BP medium also contains egg yolk the lecithin (phospholipid) in this is hydrolysed by staphylococcal (esterase) activity so that organisms are surrounded by a cleared zone in the otherwise opaque medium. The United States Pharmacopeia (1990) includes a test for staphylococci in pharmaceutical products, whereas the British Pharmacopoeia (1993) does not. 

The acid strengths shown in Table 17.3 were examined by the visual color change method using the Hammett indicators shown in Table 17.1 [43, 48]. The indicator dissolved in solvent was added to the sample in powder form in a nonpolar solvent, sulfuryl chloride [38] or cyclohexane [40]. The strength of colored materials such as S04/Fe203 and Mo03/Zr02 was estimated from their catalytic activities in comparison with those of the catalysts determined by the Hammett-indicator method. 

To titrate alkylchlorosilanes such as trimethylsilicon chloride, dimethylsilicon dichloride, methylsilicon trichloride and silicon tetrachloride, titration in methyl cyanide with 0.05 n phenazone or nitron in methyl cyanide, or with a solution of amidopyrine in benzene by visual and potentiometric methods is suggested173. The indicators used are crystal violet, dimethylaminoazobenzene, bromocresol purple, methyl orange, bromo-phenol blue and gallo sea blue (C.I.-Mordant Blue 14) the addition of benzene, toluene, chlorobenzene or carbon tetrachloride does not effect the results. 

The argentometric determination involving titration against AgN03 is carried out in neutral or slightly alkaline media (pH 6.5-10.5). The end point is indicated visually with formation of the red-brown precipitate of Ag2Cr04 which is more soluble than the precipitate of AgCl, or po-tentiometrically (silver indication electrode, calomel reference electrode). The method is used for the determination of chlorides at concentrations > 4 mg F [13, 14]. 

Halide impurities are probably the most studied of the four general categories of impurities common to ionic liquids and, besides electrochemical analysis, two methods are currently being used to determine the level of residual halide impurities in ionic liquids [12]. The titration of the ionic hquid vnth AgN O3 is still widely used but suffers from a certain solubility of AgQ in the ionic hquid under investigation. This method can be enhanced by the Vollhard method for chlorine determination where the chloride is first precipitated with excess AgNO3 followed by back-titration of the mother liquor with aqueous potassium thiocyanate [13]. This method uses a visual endpoint through the formation of a complex between thiocyanate and an iron (III) nitrate indicator. 

Comparisons to the known structure of indium DTPA and to other divalent metal DTPA bis-amide complexes indicate that the indium cation binds to the three amine nitrogen atoms, the four carboxylate oxygen atoms, and the one carboxairdde oxygen atom of the DTPA monoamide ligand. Addition of an acidic In chloride solution to a ly-ophilized DTPA-octreotide pellet at room temperature readily fomis In DTPA-octreotide, known clinically as OctreoScan. In a rat model of pancreatic carcinoma In DTPA-octreotide showed clear visualization of the tumors and rapid, primarily renal, clearance of the radiophamiaceutical/ Moreover, pretreatment with 1 mg of octreotide prevents uptake of " in DTPA-octreotide in the tumors and adrenal glands, an observation that verifies that this radiolabeled peptide binds to receptor sites. 

INFORMATION. The TLC analysis is carried out using Eastman Kodak silica gel-polyethylene terephthalate plates with a fluorescent indicator. Activate the plates at an oven temperature of 100 °Cfor 30 min and then place them in a desiccator to cool until needed. After spotting, elute the plates using methylene chloride as the solvent. Visualize the spots with a UV lamp. The course of the reaction is followed by removing small samples (2-3 drops) of solution from the hot test tube at set time intervals with a Pasteur pipet and placing them in separate -dram vials. See Technique 6Afor the method of TLC analysis and the determination of Rf values. Approximate Rf values trans = 0.72 cis = 0.64. 

Use thin-layer chromatography to obtain an analysis of the product mixture (see Prior Reading). Use methylene chloride as the elution solvent, silica gel (with a fluorescent indicator) as the stationary phase, and UV light for visualization. Typical Revalues are 0.04 for 4-nitrophenol, 0.15 for phenol, and 0.58 for 2-nitrophenol. 

The mobile phase diisopropyl ether-benzene-tetrahydrofurane-n-hexane (10 7 5 11) was used in one direction and tetrahydrofurane-/i-hexane (2 3) in the other direction on silica gel 60 plates without fluorescence indicator. Visualization was based on enzyme inhibition with cholinesterase, with butyrylthiocholine iodide serving as the substrate. After spraying with cobalt chloride, the enzyme inhibiting substances appeared as blue spots against a white background. The limit of detection was between 15-1(X) pg. (65a). 

AgN03(c9) + HiO(/). 4.113 (a) Check with litmus paper, test reactivity with carbonate, or mix with NaOH(c ) and demonstrate neutralization (use an acid-base indicator), (b) Titrate a known quantity of acid with standard NaOH( ) solution, (c) Visually compare the conductivity of an acid solution with that of a sodium chloride solution of the same molarity. 4.115 (a) The complete reaction is Pb (c9) + 2NO3 (09) -1- Na2S04( )... 

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