Method with concentration

After adding diacetyl dioxime (dimethylglyoxime) solution, nickel ions are extracted from citrate-buffered solution with chloroform, re-extracted with 1 m hydrochloric acid from the organic phase and determined by means of atomic-absorption analysis. 

Dilute 2 ml ammonium hydroxide solution I with water to 100 ml 

Dissolve 15 g diacetyl dioxime (disodium salt) (C/ H6N2Na202 8 H2O) in water and make up to 1000 ml 

Acidify the sample volume with 5 ml hydrochloric acid (1.17 g/ml) if necessary evaporate samples to 200 ml and transfer to a 250 ml separating funnel. 

Neutralize with ammonium hydroxide solution I with respect to phenolphthalein and add 3 drops of ammonium hydroxide solution I in excess. 

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It may also be obtained by evaporating the mixed carbonyl derivatives, obtained by Schiitzenberger s method, with concentrated hydriodic acid, and recrystallising from benzene. 

In natural waters rubidium and caesium ions occur at the most in traces. Either flame photometry (method 3.3.. 1) or A AS (method 3.3.4.2) following concentration by coprecipitation with potassium as tetraphenylborate is recommended for the quantitative determination of rubidium and caesium ions in water or for their semi-quantitative estimation (in the case of caesium, AAS-method 3.3 A A and method with concentration 3.3.4.5). 

It was demonstrated that concentration profiles of different components can be obtained utilizing the partial least squares method. With concentration profiles readily measurable, it is possible to obtain other quantities such as diffusion type, that is, Fickian versus non-Fickian mechanism of diffusion. The application of in situ ATR FT-IR spectroscopic imaging has been employed to investigate polymer interdiffusion of PVP and polyfethylene glycol) (PEG) under high pressure CO2 [74]. The diffusion mechanism of the system was described based on the spectroscopic imaging data, and it was found that CO2 molecules dissolved in the polymeric system greatly enhanced the interdiffusion process. 

Ammonia may be estimated by dissolving the gas in a known volume of standard acid and then back-titrating the excess acid. In a method widely used for the determination of basic nitrogen in organic substances (the Kjeldahl method), the nitrogenous material is converted into ammonium sulphate by heating with concentrated sulphuric acid. The ammonia is then driven off by the action of alkali and absorbed in standard acid. 

Alternatively a mixture of almost any solid chloride and manganese-(IV) oxide will yield chlorine when warmed with concentrated sulphuric acid. These are the most common laboratory methods but there are many others. 

Silver chloride is reduced to the metal by zinc. One of the methods of recovering silver from silver residues depends on this. The residue is first treated with concentrated hydrochloric acid and then sulphuric acid and zinc added ... 

Liquids are occasionally purified by removing impurities as constant-boiling mixtures, or by shaking with concentrated sulphuric acid and subsequently separating the dried liquid from the acid the second method is therefore limited to liquids which are insoluble in, and chemically unaffected by, the strong acid e.g., benzene, anhydrous chloral). 

Method- 3. From platinum metal or platinum residues. Dissolve the platinum metal or platinum residues in aqua regia, evaporate just to dryness several times with concentrated hydrochloric acid, dissolve the final residue in a httle water and precipitate as ammonium chloro-platinate with excess of saturated ammonium chloride solution. Filter and dry the precipitate at 100°. Then proceed according to Method 1. 

Quantitative eomparisons of aromatic reactivities were made by using the competitive method with solutions of nitronium tetrafluoroborate in sulpholan, and a concentration of aromatic compounds 10 times that of the salt. To achieve this condition considerable proportions of the aromatic compoimds were added to the medium, thus depriving the sulpholan of its role as true solvent thus, in the nitration of the alkyl- and halogeno-benzenes, the description of the experimental method shows that about 50-60 cm of mixed aromatic compounds were dissolved in a total of 130 cm of sulpholan. 

The cleanup of this oil is exactly like that which was done in Method 1. The oil is dissolved in about SOOmL of 3N HCl and the solution extracted with TOOmL of DCM. The chemist remembers that in this particular case the MDMA or meth is going to stay in the HCl/water but that unreacted, valuable MD-P2P or P2P is going to be in that DCM so it, of course, is saved. The HCl/MDMA solution is then basified with concentrated NaOH so that at around pH 9 the happy little beads of final, freebase product will appear in the solution. As usual, the oil is extracted with DCM, dried through Na2S04 and the DCM removed by distillation. The final product here is usually a little darker in color than the product achieved in Method 1, but it is still remarkably clean and may be crystallized as is with the crystallization process removing most of the color impurities. Of course the chemist may wish to vacuum distill to afford clear product. The average yield with this method is 60-70%. 

Ethyl Acetate is allowed to mix with concentrated Ammonia solution for several days to make Acetamide. This is a very attractive method because all the reagents involved are easy to acquire and cheap. 

Hydration of alkenes by this method however is limited to monosubstituted alkenes and disubstituted alkenes of the type RCH=CHR Disubstituted alkenes of the type R2C=CH2 along with trisubstituted and tetrasubstituted alkenes do not form alkyl hydrogen sulfates under these conditions but instead react m a more complicated way with concentrated sulfuric acid (to be discussed m Section 6 21)... 

A sample is to be analyzed following the protocol shown in Figure 15.2, using a method with a detection limit of 0.05 ppm. The relationship between the analytical signal and the concentration of the analyte, as determined from a calibration curve is... 

Qualitative Analysis. Several quaUtative analyses can be employed. For example, in the oxamide method (59), oxaUc acid is first heated at approximately 200°C with concentrated aqueous ammonia in a sealed tube. When thiobarbituric acid is added and heated to 140°C, a condensed compound of red color forms. The analysis limit is 1.6 pg. In the diphenylamine blue method (59,60), oxaUc acid is heated with diphenylamine to form a blue color, aniline blue. The analysis limit is 5 pg. 

Critical Micelle Concentration. The rate at which the properties of surfactant solutions vary with concentration changes at the concentration where micelle formation starts. Surface and interfacial tension, equivalent conductance (50), dye solubilization (51), iodine solubilization (52), and refractive index (53) are properties commonly used as the basis for methods of CMC determination. 

Older methods of stripping used with concentrations below 1000 ppm utilize a stream of air flowing countercurrent to the brine stream. The bromine is then recovered from the air with wet scrap iron, ammonia, sodium carbonate, or sulfur dioxide (23—25). 

Experiment diffusion coefficients are scarce and not highly accurate, especially in the liquid phase, leading to prediction methods with marginal accuracy. However, use of the v ues predicted are generally suit le for engineering calculations. At concentrations above about 10 mole percent, predicted values should be used with caution. Diffu-sivities in liquids are lO -lO times lower than those in gases. 

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