PH papers

Nickel sulfamate is more soluble than the sulfate salt, and baths can be operated using higher nickel concentrations and higher currents. Sulfamate baths have been found to have superior microthrowing power, the abiUty to deposit in small cracks or crevices. Using one nickel salt, only a hydrometer and pH paper are needed to control the bath. A small amount of chloride salt was added as a proprietary. Highly purified nickel sulfamate concentrates are commercially available that can be used to make up new plating baths without further purification. 

Checking bath concentration Acid content can be cheeked with the help of a pH paper. If this indicates more than 3.5, add more acid to make it less than this reading. 

The bath water may be checked for any acid traces with the help of a pH paper. This should give a reading above 6, preferably around 7. 

In a 1-1. three-necked round-bottomed flask equipped with an eflicient stirrer, a reflux condenser, and a thermometer (Note 1) are placed 500 ml. of glacial acetic acid (Note 2), 29.0 g. (0.19 mole) of -aminoacetanilide (Note 3), 40 g. (0.26 mole) of sodium perborate tetrahydrate, and 10 g. (0.16 mole) of boric acid. The mixture is heated with stirring to 50-60° and held at this temperature for 6 hours. Initially the solids dissolve but, after heating for approximately 40 minutes, the product begins to separate. At the end of the reaction period, the mixture is cooled to room temperature and the yellow product is collected on a Buchner funnel. It is washed with water until the washings are neutral to pH paper (Note 4) and then dried in an oven at 110°. The yield of 4,4 -bis(acetamido)a2obenzene, m.p. 288-293° (dec.), is 16.5 g. (57.7%). It is used as such for the hydrolysis step (Note 5). 

Bromothymol blue or commercial universal indicator pH paper (graduated in 0.2-pH units) may be used as external indicators. 

A 1.5 to 2 M solution of methylsulfinyl carbanion in dimethyl sulfoxide is prepared under nitrogen as above from sodium hydride and dry dimethyl sulfoxide. An equal volume of dry tetrahydrofuran is added and the solution is cooled in an ice bath during the addition, with stirring, of the ester (0.5 equivalent for each 1 equivalent of carbanion neat if liquid, or dissolved in dry tetrahydrofuran if solid) over a period of several minutes. The ice bath is removed and stirring is continued for 30 minutes. The reaction mixture is then poured into three times its volume of water, acidified with aqueous hydrochloric acid to a pH of 3-4 (pH paper), and thoroughly extracted with chloroform. The combined extracts are washed three times with water, dried over anhydrous sodium sulfate, and evaporated to yield the jS-ketosulfoxide as a white or pale yellow crystalline solid. The crude product is triturated with cold ether or isopropyl ether and filtered to give the product in a good state of purity. 

A less accurate but more colorful way to measure pH uses a universal indicator, which is a mixture of acid-base indicators that shows changes in color at different pH values (Figure 13.5, p. 359). A similar principle is used with pH paper. Strips of this paper are coated with a mixture of pH-sensitive dyes these strips are widely used to test the pH of biological fluids,... 

The recovered resin can be reconverted to the hydroxide form by eluting a column of the material with aqueous 10% sodium hydroxide until it is free of halide ion (silver nitrate-nitric acid test) and then with water until the eluent is no longer alkaline to pH paper. 

Care should be taken to add the sodium bicarbonate in small amounts initially in order to avoid excessive frothing. The mixture was tested with pH paper to establish that neutralization was complete. 

Measurement of pH was performed using a Metrohm model 691 pH meter equipped with a Metrohm combined LL micro pH glass electrode calibrated prior to use with pH = 2 and 9 buffers. The checkers found that adjustment to a lower pH led to product with higher amounts of inorganic impurities. The checkers also found that the use of pH paper results in different pH values as compared to the pH meter. 

Filter the wet resin and rinse with distilled water. Repeat the washing procedure until the washing water is neutral to pH paper. Rinse with three 100-ml portions of methanol. Evaporate off the remaining methanol in a rotary film evaporator under vacuum, rotating slowly at 40°C, until visibly dry. 

Place 200 g of ion exchange resin Dowex 50W-X8, 100-200 mesh, hydrogen form into a 1-L beaker and add 600 ml of 1 M hydrochloric acid solution. Allow to stand for 24 h with occasional swirling. Decant off the liquid and filter off the resin using filter funnel and paper. Place the resin in a beaker and add 600 ml of distilled water. Stand for 24 h with occasional swirling. Decant off the liquid and repeat the washing procedure until the wash water is neutral to pH paper. 

Figure 17-3 shows the range of pH and hydronium ion concentrations. The measurement of pH is a routine operation in most laboratories. Litmus paper, which turns red when dipped in acidic solution and blue when dipped in basic solution, gives a quick, qualitative indication of acidity. As Figure 17-4 shows, approximate measures of pH can be done using pH paper. Universal pH paper displays a range of colors in response to different pH values and is accurate to about 0.5 pH unit. For quantitative pH determinations, scientists use pH meters. 

To prepare the mild-alkali-extract, dry watermelon cell walls were suspended in a solution of 0.1 N NaOH, and allowed to react with stirring at room temperature for 15 minutes. A pH of 13, as indicated by pH paper, was kept constant during this period by addition of 0.1 N NaOH. To ensure complete reaction, the treatment was continued overnight at 4 °C. The soluble portion was separated by centrifugation at 10,000 RPM for 20 minutes in a Sorval GSA rotor. The insoluble portion was washed twice with water. The supernatants were combined and, after neutralization to pH 7.0 with acetic acid, dialyzed against distilled water and freeze dried. 

Dichloromethane partition. Add 100 mL of deionized water to the round-bottom flask. Transfer the sample to a 500-mL separatory funnel and add 1 mL of phosphate buffer and 1 g of sodium sulfate. Adjust the pH to 7 with 1 M phosphoric acid (approximately 0.75 mL), checking that the pH is approximately 7 with pH paper. Add 100 mL of dichloromethane to the separatory funnel, rinsing the round-bottom flask with portions of this before addition to the separatory funnel. Shake the separatory funnel vigorously (with occasional venting) for 1 min, and allow the phases to separate. Drain the dichloromethane through sodium sulfate (approximately 50 g... 

The jar was shook to mix the acid and water. Immediately afterwards the pH of the water was tested. The pH was 1 using pH papers to measure. (Compare pH within 30 seconds with litmus.)... 

In the fume hood, add PBS (prewarmed in microwave to save time ) to a flask containing a stirbar. With constant stirring, add the weighed powdered paraformaldehyde. Heat to hot-not-boiling ( 60°) on a heater/ stir plate, until solution clears. Check that pH is around 7.5 using pH paper. 

The washing process was performed until the aqueous phase was acidic to pH paper. The checkers found that gas pressure build-up was common, so the separatory funnel should be vented frequently during acidification. 

In a 100-ml. pressure vessel (Note 1) are placed 14.0 g. (0.050 mole) of 3-bromopyrene (Note 2), 0.5 g. of copper bronze powder (Note 3), 1.5 g. of cuprous oxide (Note 4), and 60 ml. of 10% aqueous sodium hydroxide (Note 5). The vessel is sealed, heated rapidly with shaking to 275-280°, and maintained at this temperature for 3 hours. The vessel is allowed to cool and is opened, and the contents are poured into a 500-ml. beaker containing 200 ml. of water (Note 6). The mixture is filtered, and the filter cake is washed with water until the washings become neutral to pH paper. The combined filtrate and washings, which show a blue fluorescence, are made acid to Congo red paper with 20% aqueous sulfuric acid. The precipitate is collected by filtration, washed free of acid with water, and dried in an oven at 100° to give ca. 9 g. of a gray solid. 

When mentioned, deactivated silica gel means that it was treated with 5% triethy-lamine in pentane and the column was eluted with the same solvent mixture until the outflowing eluent was basic according to pH paper. 

Ergotamine tartrate (lOg) is added to a stirred de aerated (nitrogen stream) solution of 38 g potassium hydroxide in 100 ml of methanol and 200 ml of water. The solution turns pink to red. The solution is heated to reflux and the methanol is slowly removed using a partial takeoff. Methanol is allowed to distill until the pot temperature reaches 90-95° C. The mixture is then maintained at total reflux until the evolution of ammonia ceases (hold pH paper in outlet of reflux condenser to test for ammonia). Nitrogen should be bubbled through the mixture to entrain the ammonia. 

The basic compound (3). Add ammonium hydroxide until the solution turns basic (test with litmus or pH paper). The p-toluidine, or organic base (3), is regenerated. 

The trend towards increased calcium carbonate usage and therefore neutral pH paper making has meant that there has been a steady decline in the use of rosin and alum and a concomitant increase in the use of sizes which are effective at higher pH. Commercially the most important in this group are the alkenyl succinic anhydrides (ASA) and the alkyl ketene dimers (AKD). These are able to esterify fibre surfaces directly and are more effective at neutral to high pH. 

The exhaust gas is very acidic (pH < 1 using wet pH paper), and therefore should be scrubbed by bubbling through a solution of potassium hydroxide. 

Pour a small volume of one of the solutions into the well of a spot plate. Test the solution using universal pH paper. By comparing the colour of the paper, estimate the pH of the solution. Record your results in you table. 

The reduction was done essentially as described previously (Robins, 1976). After several washings with 0.9% (w/v) sodium chloride, 0.05 M sodium phosphate, pH 7.4, at 4°C, the stirred demineralized root powder was reduced with 0.71 g sodium borohydride, an estimated one-twentieth of the collagen mass. After one hour, the solution was acidified (pH < 4, pH paper) to inactivate remaining borohydride. Thereafter, the pH was readjusted to 7.5. The solution was centrifuged and the pellets were hydrolyzed by heating for 24 hours at 112°C in 6 M HCl under N2 in bottles with Teflon-sided screw caps. The dark hydrolyzate was paper-filtered, evaporated under reduced pressure at 50°C, and mixed with 5 ml 0.1 M acetic acid. The hydrolyzate was assayed for hydroxyproline. 

Saturated ammonium sulfate (enzyme grade) Dissolve 800 g of ammonium sulfate in 1 L of hot BBS. Filter the solution through Whatman no. 1 paper and cool to room temperature. Confirm that the pH of the solution is 8.0 with a strip of narrow-range pH paper. Cool the saturated ammonium sulfate solution and store at 4°C (see Note 2). 

The pH of saturated ammonium sulfate can be checked either directly with narrow-range pH paper or after 10-fold dilution with a pH meter. Excess ammonium sulfate should precipitate out in the cold. The solution above the ammonium salt is considered to be 100% saturated. 

Neutralize the column matrix immediately by washing with 20 mL of BBS. Ensure that the column is neutralized by checking the effluent with pH paper. 

Equilibrate the column with PBS, pH 7.4. Confirm that the column pH has been neutralized by testing the effluent with pH paper. 

Neutralize the column immediately by washing with 20-30 mL of PBS, pH 7.4. Check the pH of the column effluent with pH paper to ensure that the pH is back to neutrality. 

Add two drops of 1% PEG (20,000 mol wt) to 5-mL aliquots of the colloidal gold to avoid clogging the pH meter when adjusting the pH. Do not add the PEG to the colloidal gold stock. Discard aliquots after reading pH. Alternatively, narrow-range pH paper can be used. 

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