Methyl red test

4 DETECTION OF SPECIFIC METABOLIC END PRODUCTS 4.1 Methyl Red Test 

This determines whether the organism can produce sufficient acid from glucose to reduce the pH to 4.5 or below and maintain it there. It is used for the differentiation of Enterobacteria. 

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According to Levine, the methyl red test checks with the Voges-Proskauer reaction. The test for B. coli of fecal origin is the development of a red coloration in the medium after twelve hours incubation. 

After 5 days apply methyl red test and Voges-Proakauer test to dextrose broth. 

Several properties of the filler are important to the compounder (279). Properties that are frequentiy reported by fumed sihca manufacturers include the acidity of the filler, nitrogen adsorption, oil absorption, and particle size distribution (280,281). The adsorption techniques provide a measure of the surface area of the filler, whereas oil absorption is an indication of the stmcture of the filler (282). Measurement of the sdanol concentration is critical, and some techniques that are commonly used in the industry to estimate this parameter are the methyl red absorption and methanol wettabihty (273,274,277) tests. Other techniques include various spectroscopies, such as diffuse reflectance infrared spectroscopy (drift), inverse gas chromatography (igc), photoacoustic ir, nmr, Raman, and surface forces apparatus (277,283—290). 

Another recipe for a universal indicator is as follows 0.05 g of methyl orange, 0.15 g of methyl red, 0.3 g of bromothymol blue, and 0.35 g of phenolphthalein in 1 L of 66 per cent ethanol. The colour changes are pH up to 3, red pH 4, orange-red pH 5, orange pH 6, yellow pH 7, yellowish-green pH 8, greenish-blue pH 9, blue pH 10, violet pH 11, reddish-violet. Several universal indicators are available commercially as solutions and as test papers. 

Biochemical tests are usually performed after pure cultures have been obtained. The standard indole, methyl red, Voges-Proskauer, citrate, and litmus milk tests may be used to show important physiological characteristics. To study the functional diversity of bacteria, the utilization of carbohydrates, amines, amides, carboxylic acids, amino acids, polymers, and other carbon and nitrogen sources can be tested.28 Dilution-based most-probable number (MPN) techniques with phospholipid fatty acids as biomarkers have been employed for studying different bacterial species in lakes.40 The patterns of antibiotic resistance in bacteria isolated from natural waters have been useful for identifying sources of water pollution.34... 

In order now to remove proteins from the thin sludge it is vigorously stirred with 0-05 A-acetic acid in amount just sufficient to change the colour of methyl red (pH=4) (test with a sample), and is then filtered as above after shaking with a little kieselguhr if necessary. The filtrate is made neutral to litmus with dilute ammonia and in this condition, protected by a little toluene, can be kept unchanged for several days. 

Pour 2-3 ml each of 1 iV solutions of hydrochloric and acetic acids, sodium hydroxide, and an aqueous ammonia solution into test tubes. Pour one or two drops of a phenolphthalein solution into each of the tubes and see whether the colour of the solution changes. Perform similar experiments with other indicators, namely, methyl red, litmus, methyl orange (see Appendix 1, Table 6). Enter your observations into your laboratory notebook using Form 14. 

Neutralize the solution with ammonia up to a weakly acidic reaction (pH 3-4), using methyl red as an indicator. Test with the indicator as follows apply several drops of it onto filter paper placed on a glass plate, and in the course of neutralizing the solution being tested take a sample of it with a glass rod and transfer it onto the filter paper with the indicator. 

Dissolve the roasted substance (what is its composition ) in water and test the reaction of the solution with phenolphthalein, methyl red, and a universal indicator. Comment on your observations. 

Acidity (as H2SO4) Dilute 9 mL (10 g) of sample in 90 mL of carbon dioxide-free water, add methyl red TS, and titrate with 0.02 N sodium hydroxide. The volume of sodium hydroxide solution should not be more than 3 mL greater than the volume required for a blank test on 90 mL of the water used for dilution. 

Other Cinchona Alkaloids Dissolve about 2.5 g in 60 mL of water in a separator, add 10 mL of 6 A ammonium hydroxide, extract the mixture successively with 30 mL and 20 mL of chloroform, and evaporate the combined chloroform extracts to dryness on a steam bath. Dissolve 1.5 g of the residue in 25 mL of alcohol, dilute the solution with 50 mL of hot water, add 1 A sulfuric acid (about 5 mL) until the solution is acid, using 2 drops of methyl red TS as the indicator, and neutralize the excess of acid with 1 A sodium hydroxide. Evaporate the solution to dryness on a steam bath, powder the residue, and agitate it in a test tube with 20 mL of water at 65° for 30 min. Cool the mixture to 15°, macerate it at this temperature for 2 h with occasional shaking, and then filter it through a filter paper (8 to 10 cm). Transfer 5 mL of the filtrate, at a temperature of 15°, to a test tube, and mix it gently, with shaking, with 6 mL of 6 A ammonium hydroxide (which must contain between 10% and 10.2% of NH3, have a temperature of 15°, and be added at once). A clear liquid is produced. 

Filter immediately and cool to RT. Test the filtrate by adding two drops of phenophthalein and then two drops of methyl red. If colorless to phenolphthalein and yellow to methyl red, acidity may be reported as none... 

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