Indicators, methyl orange

Xylene cyanole-methyl orange indicator, Schoepfie modification (for partially color blind operators) dissolve 0.75 g xylene cyanole FT (Eastman No. T 1579) and 1.50 g methyl orange in 1 liter of water. 

Procedure. Weigh out accurately from a weighing bottle about 0.2 g of the pure sodium carbonate into a 250 mL conical flask (Note 1), dissolve it in 50-75 mL of water, and add 2 drops of methyl orange indicator (Note 2) or preferably of methyl orange-indigo carmine indicator (Section 10.9), which gives a very much more satisfactory end point (Note 3). Rinse a clean burette three times with 5 mL portions of the acid fill the burette to a point 2-3 cm above the zero mark and open the stopcock momentarily, in order to fill the jet with liquid. Examine the jet to see that no air bubbles are enclosed. If there are, more liquid must be run out until the jet is completely filled. Re-fill, if necessary, to bring the level above the zero mark then slowly run out the liquid until the level is between the 0.0 and 0.5 mL marks. Read the position of the meniscus to 0.01 mL (Section 3.12). 

Primarily the sum of carbonate, bicarbonate and hydrate ions in water, but phosphate, silicate etc. may also contribute partially to alkalinity. Normally expressed as ppm (mg/1) CaC03. Phenolphthalein alkalinity (P Aik.) is that portion of alkalinity titrated with acid to pH 8.2 end-point, while total alkalinity (T Aik. or M Aik.) is that titrated with methyl orange indicator to pH 4.2 endpoint. 

An alternate method consists of titrating aq NH2OH with a std acid using a methyl orange indicator... 

Army). Mix the original wet sample and transfer ca 10 g portion to a tared Gooch or Selas No 2001 crucible. Wash with five 20 ml portions of cold (0 to 15°) distd w, which has been boiled and cooled prior to the test. Allow each portion of w to remain in contact with LA for 3 mins. Add to the filtrate 5 drops of 0.1% methyl orange indicator and note if the sample is free from acidity as shown hy the absence of a red tinge... 

Quantitative Determination. — Dilute 2 gm. of the ammonia water with about 50 cc. of water, and titrate with normal hydrochloric acid, using methyl orange indicator. 

The lithium carbonate concentration was measured by acidimetric titration with methyl orange indicator. The calcium sulfate and calcium hydroxide concentrations were determined by titration with disodium dihydrogen Versenate [the disodium salt of (ethylenedinitrilo) tetraacetic acid], with added magnesium chloride. A buffer of ammonium chloride in ammonium hydroxide was employed. The indicator was Erio-chrome Black T. A special high purity calcium carbonate in hydrochloric acid was used as a standard. Because of the high concentration of sodium sulfate it was con-... 

C. Diluted hydrochloric acid (21 0 1HC1) or alternately 600 ml concentrated HC1 with 1200 ml H2O adding 9 ml 0.1% methyl orange indicator. 

Twenty-two mg. of a white solid, compound A, is dissolved in 25 ml of 0.1 N HC1. An odorless but flammable gas is released whose volume, corrected to standard conditions, is 89.6 cc. Methyl orange indicator is added to the solution, and a back titration, using 0,1 N NaOH is performed 15 ml of NaOH are necessary. At this end point, an excess of glycerol and a few drops of phe-nolphthalein are added and the solution again titrated with 0.1 N NaOH, the second titration requiring 10.0 mL What is compound A ... 

Methyl orange indicator (0.1%). Dissolve 0.1 g of methyl orange in 100 ml of ethyl alcohol. 

The nitric acid produced in the combustion was determined by titrating with standardized alkali using a methyl orange indicator. The thermal correction was calculated on the basis 14.0 kcal./mole evolved for each mole of aqueous acid formed. A correction was made for the average firing energy, 12.2 cal. 

When the acid has drained to bed level, rinse with deionized water at 1 BV/2 minutes until the eluate is just alkaline to screened methyl orange indicator. 

Titrate the mixture with 0.1 N NaOH using screened methyl orange indicator. 

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