Tube dilution test

Heating with soda-dime. See Section 3, p. 327, Condense the aniline which distils over in a test-tube, dilute with water and add bleaching powder (or NaClO) solution. Note the iolet coloration. 

The reagent must be carefully protected from moisture as it is comparatively easily hydrated to the acid, m.p. 216-218° (sealed capillary tube). Dilute aqueous solutions of an alcohol should be treated with solid potassium carbonate and the alcohol layer used for the test. 

Place an appropriate volume of standard lead solution which corresponds to each of five concentration levels in a Nessler tube, and add water to make up to 40 mL. Add 2 mL of dilute acetic acid and water to make up to 50 mL, and designate it as the test solution. Three tubes of test solution at each concentration level are prepared for separate runs. 

Pour several drops of bromine water into a test tube, dilute it with 5 ml of distilled water, and add 5-10 drops of chloroform. Thoroughly stir the contents of the test tube. Explain the observed phenomenon. Perform a similar experiment with other organic solvents (petrol, benzene, carbon disulphide, carbon tetrachloride). 

Put several pieces of chromium into test tubes and test its reaction with water, alkalies, and also with dilute and with concentrated solutions of hydrochloric, sulphuric, and nitric acids (in the cold and with heating). Write the equations of the reactions. What position does chromium occupy in the electrochemical series of metals ... 

SET UP APPARATUS FOR MAKING HYDROGEN SULFIDE [SEE PAGE 53). POUR SOLUTION OF MnClj INTO TEST TUBE. DILUTE IT IF NECESSARY. LEAD H,S INTO IT. YOU GET MANGANESE SULFIDE. 

V IN ONE TEST TUBE, DILUTE SOME FERRIC CHLORIDE SOLUTION WITH WATER. 

Depending on the number of cells used in the centrifugation step, there will be a variable cell concentration in the tubes to test. Dilutions may be necessary. 

Bromide test (a) If iodide is present, it must be removed by treating one-third of the solution with 5 drops dilute H2S04 and 2 drops of 30 per cent NaN02 solution (chloride-free). Boil down gently to 3-4 drops and allow to cool. Transfer the solution to a centrifuge tube and test for bromide as under (b). 

Experiment 48. Supplies Test tubes, dilute sulphuric, nitric, and hydrochloric acids, acetic acid, glass rod, litmus paper (both colors), zinc, calcium carbonate (marble), lime water. 

These usually employ liquid media but can be modified to involve solid media. Doubling dilutions— usually in the range 0.12-256 mg/L—of the antimicrobial under test are prepared in a suitable broth medium, and a volume of log phase cells is added to each dilution to result in a final cell density of around 5 x 105 CFU/ml. After incubation at 35°C for 18 hours, the concentration of antimicrobial contained in the first clear tube is read as the MIC. Needless to say, dilution tests require a number of... 

Material Test tubes diluted solutions of silver nitrate, sodium chloride, hydrochloric acid, barium chloride, sodium sulfate, sulfuric acid. 

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