Sodium—continued standard solution

Sensitiveness To 10 mL of a 1 200,000 solution in a mixture of equal parts (v/v) of methanol and water add a 1 100 solution of sodium hydroxide until the pH is 10. The solution is pure blue and free from cloudiness. Add 0.2 mL of Magnesium Standard Solution (10 jxg Mg ion). The color of the solution changes to red-violet, and with the continued addition of magnesium ion, it becomes wine red. 

Use a similar concentration of a barbiturate (amobarbital), not contained in the sample and that is completely resolved from secobarbital, as the internal standard. Inject 5 p,l of the sample plus internal standard solution into the gas chromatograph, and then a standard solution of secobarbital containing the internal standard. For dosages containing sodium secobarbital, extract the secobarbital from 10% HC1 with CHC13, evaporate and continue as above with methanol. 

H.OJ and 5 ml of 10% potassium hydroxide (or sodium hydroxide). Boil the solution gently for 1 h to oxidize Cr to C.f + and to get rid of excess peroxide. Add 10 ml of 6 N H,SO to acidify the solution. After standing in the dark for 5 min, add 20 ml of 10% (w/w) potassium iodide. The solution turns to a dark reddish brown owing to the formation of iodine. Titrate the iodine in the solution with 0.1 N standard solution of sodium thiosulphate until the colour of the solution turns to yellow. Add 1-2 ml of starch solution (1% w/w) as an indicator. The colour of the solution turns to dark blue. Continue titration until the colour just disappears. Record the volume of the standard solution of sodium thiosulphate used (V ). The concentration C (g 1 ) of initial chromium sulphate solution can be calculated by the following equation ... 

To the remaining sample and standard solutions add, in order, 15 ml of buffer solution pH 7 5, 2 ml of 10 per cent sodium bisulphite and 3 ml of 0-4N sodium hydroxide. Place the flasks in boiling water for exactly five minutes, add 12 ml of 5N hydrochloric acid, mix and continue heating for a further two minutes. Cool the flasks immediately. Dilute all solutions to volume with water and measure the extinctions of the acid-treated sample and standard solutions at 445 mju in a 1-cm... 

A calibration graph is plotted using aliquots of the boron standard solution (H), containing 0.25 to 3 pg of boron. These aliquots are transferred into platinum dishes containing 3 ml sodium hydroxide-glycerol solution (D). After evaporation to dryness on a boiling water bath, the procedure is continued as described above. A solution without boron addition is used as blank. 

In the indirect method, the ammonium salt (other than the carbonate or bicarbonate) is boiled with a known excess of standard sodium hydroxide solution. The boiling is continued until no more ammonia escapes with the steam. The excess of sodium hydroxide is titrated with standard acid, using methyl red (or methyl orange-indigo carmine) as indicator. 

Procedure. Pipette 25 mL of the standard OAM sodium chloride into a 250 mL conical flask. Add 10 drops of either fluorescein or dichlorofluorescein indicator, and titrate with the silver nitrate solution in a diffuse light, while rotating the flask constantly. As the end point is approached, the silver chloride coagulates appreciably, and the local development of a pink colour upon the addition of a drop of the silver nitrate solution becomes more and more pronounced. Continue the addition of the silver nitrate solution until the precipitate suddenly assumes a pronounced pink or red colour. Repeat the titration with two other 25 mL portions of the chloride solution. Individual titrations should agree within 0.1 mL. 

B) With standard sodium thiosulphate solution. Sodium thiosulphate solution, which has been recently standardised, preferably against pure potassium iodate, is employed. Transfer 25 mL of the iodine solution to a 250 mL conical flask, dilute to 100 mL and add the standard thiosulphate solution from a burette until the solution has a pale yellow colour. Add 2 mL of starch solution, and continue the addition of the thiosulphate solution slowly until the solution is just colourless. 

After the addition of the potassium iodide solution, run in standard 0.1M sodium thiosulphate until the brown colour of the iodine fades, then add 2 mL of starch solution, and continue the addition of the thiosulphate solution until the blue colour commences to fade. Then add about 1 g of potassium thiocyanate or ammonium thiocyanate, preferably as a 10 per cent aqueous solution the blue colour will instantly become more intense. Complete the titration as quickly as possible. The precipitate possesses a pale pink colour, and a distinct permanent end point is readily obtained. 

The concentration of the potassium bromate can be checked by the following method pipette 25 mL of the solution into a 250 mL conical flask, add 2.5 g of potassium iodide and 5 mL of 3M sulphuric acid. Titrate the liberated iodine with standard 0.1M sodium thiosulphate (Section 10.114) until the solution is faintly yellow- Add 5 mL of starch indicator solution and continue the titration until the blue colour disappears. 

Prepare a set of standards by dissolving cysteine in 0.1M sodium phosphate, pH 8.0, at an initial concentration of 2mM (3.5mg/ml) and serially diluting this solution (1 1) with reaction buffer down to at least 0.125 mM. This will produce five solutions of cysteine for generating a standard curve. If a more dilute concentration range is required, continue to serially dilute until a set of standards in the desired range is obtained. 

The palladium catalyst supported on the dendrimer with 24 phosphine end groups (2) was used in a CFMR. In the continuous process a solution of allyl trifluoroacetate and sodium diethyl 2-methylmalonate in THF (including -decane as an internal standard) was pumped through the reactor. Figure 4 shows the conversion as a function of the amount of substrate solution (expressed in reactor volumes) pumped through the reactor. The reaction started immediately after the addition of the catalyst, and the maximum conversion was reached after two reactor volumes had passed, whereupon a drop in conversion was observed. It was inferred from the retention of the dendrimer (99.7% in dichloromethane) that the decrease was not caused by dendrimer depletion, and it was therefore ascribed to the... 

NOTE Solution (either water or sample) must be continuously aspirated into the flame. Therefore, ensure that the sample delivery tube is immersed in solution at all times. Rinse all glassware with distilled or de-ionized water before preparing standards to avoid sodium contamination. Ensure that you have prepared all of your standards before proceeding with the experiment. 

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