Blue litmus paper, acid testing

Oxidation, (i) Dissolve 5 g. of potassium dichromate in 20 ml. of dil. H2SO4 in a 100 ml. bolt-head flask. Cool and add 1 ml. of methanol. Fit the flask with a reflux water-condenser and warm gently a vigorous reaction soon occurs and the solution turns green. The characteristic pungent odour of formaldehyde is usually detected at this stage. Continue to heat for 3 minutes and then fit the flask with a knee-tube (Fig. 59, p. 100) and distil off a few ml. Test the distillate with blue litmus-paper to show that it is definitely acid. Then apply Test 3 p. 350) for formic acid. (The reflux-distillation apparatus (Fig. 38, p. 63) can conveniently be used for this test.)... 

Use a stirring rod to transfer 1 drop of hydrochloric acid (test tube number 1) to a piece of red litmus paper. Then transfer 1 drop of hydrochloric acid to a piece of blue litmus paper. 

Acidity in Explosives Test is one of the std tests for the detn of purity of expls and propellants. A rapid qualitative method consists of touching a sample with a strip of moistened indicator paper, such as blue litmus paper. 

LIGHT SULFUR IN BOTTLE CAP. LOWER BURNING SULFUR INTO JAR. WHEN JAR IS FULL OF FUMES, REMOVE SULFUR. ADD A FEW ml WA TER. SHAKE. AS S02 DISSOLVES IN WATER IT FORMS A WEAK ACID— SULFUROUS ACID, HjSO,. TEST FOR ACID WITH BLUE LITMUS PAPER. 

MIX CALCIUM ACETATE WITH AN EQUAL AMOUNT OF SODIUM Bl-SULFATE. PLACE IN DRY TEST TUBE. HEAT GENTLY. YOU GET SHARP ODOR OF ACETIC ACID. MOISTENED BLUE LITMUS PAPER AT MOUTH OF TUBE TURNS RED. 

Black Pepper Oil, 47, 572, (S 1)5 Black Peppier Oleoresin, 391, 392 Blank Tests, 4 Blank Titration, Residual, 4 Bleached Starch, 159 Bleidner Apparatus, (S3)17 Blue Litmus Paper, 861 Bois de Rose Oil, 47, 576 Boric Acid-Potassium Chloride, 0.2 M, 848... 

Test the contents of both jars with red and blue litmus paper to see which solution is acid and which solution is alkaline. Place the jar of acid directly in front of you. Place the alkaline solution to the right and slightly behind the acid (unless you are left-handed). Now, with the dropper near the calcium hydroxide, add 3 drops of it to the acetic acid, stir with the spoon near the acetic acid, and test the new solution with blue litmus paper. Repeat this procedure over and over, counting the drops carefully, and noting the amount of change in... 

Experiment 52. — Dissolve a small piece of sodium hydroxide in an evaporating dish half full of water. Slowly add dilute hydrochloric acid, until a drop taken from the dish by means of a glass rod reddens blue litmus paper. Then evaporate to dryness by heating over a piece of wire gauze. Since the residue mechanically holds traces of the excess of hydrochloric acid added, it is necessary to remove this acid before applying any test. Heat the dish until all the yellow color disappears, then moisten the residue carefully with a few drops of warm water and heat again to remove the last traces of acid. This precaution is essential to the success of the experiment. Test a portion of the residue with litmus paper to find whether it has acid, basic, or neutral properties. Taste a little. Test (a) a solution of the residue for a chloride, and (b) a portion of the solid residue for sodium. Draw a definite conclusion from the total evidence. 

For,1 firework use the sulphuric acid content mu t be low especially if it is used in combination with chlorate. The acidity is tested with blue litmus paper to see whether the wash water of the sulphur changes its colour to red or not. /... 

Properties of Formic Acid (Section 100).—(a) Odor of formic acid.—Note the odor of the solution obtained in experiment 86 above, and test the solution with blue litmus paper. 

Illustration Take a piece of blue litmus paper and dip it in a test tube containing hydrochloric acid, observe the change in colour (it turns red). Take another piece of blue litmus paper and dip it in a test-tube containing nitric acid. Observe the change in colour (it turns red). Repeat the experiments with other acids in different test tubes (e.g. oxalic acid, acetic acid etc.). (In each case blue litmus turns red). 

Take another piece of blue litmus paper and dip it in a test-tube containing nitric acid. Observe the change in colour. (It turns red.)... 

Red and blue litmus paper is used for testing alkaline and acid solutions. For instance, if we had a solu-tion and wished to know whether it was a base or acid, we would take a piece of red or blue litmus paper and dip it in it. If the red paper turned blue it would indicate a base. If it remained red we would not know whether or not it was neutral or alkaline. Therefore, we would try it with blue litmus paper. If the blue litmus paper would turn red we would then under-... 

Put a drop of dilute hydrochloric acid, of dilute sulphuric acid, and of dilute nitric acid on each of three pieces of blue litmus paper. (1) What is the action of acids on blue litmus paper (2) What is a test for an acid Dip the end of a glass rod into the water into which you passed chlorine in Experiment 21 and touch a piece of blue litmus paper with it. (3) What change in color takes place hnmediatelyf (4) What kind of a compound or compounds does the water contain (5) What are the names of the substances formed by the action of chlorine on water (6) Write the equation for the reaction. Cautiously smell the solution. (7) Does it still contain chlorine (8) Did the reaction, the equation of which you have just written, proceed to completion (9) What is the evidence (10) What substances are present in chlorine water (11) Which of the substances is the bleaching agent in chlorine water (12) What are your reasons for ascribing the action to this compound rather than to the other substances present ... 

Directions Perform this experiment in the hood. Measure out into an evaporating dish 8 c.c. of water and add to it 10 c.c. of concentrated sulphuric acid. (Do not add the water to the acid.) While the solution is cooling set up an apparatus like the one for the preparation of chlorine, Experiment 21. Put 10 grams of sodium chloride into the test tube and pour the acid down the thistle tube. When the salt has become thoroughly moistened with the acid, heat the test tube with a low flame, holding the burner in your hand. To determine when the bottle has been filled, hold a piece of wet blue litmus paper at its mouth. Do not consider the bottle full when the first test is obtained but continue generating the gas until it overflows in some quantity. Collect four bottles full and cover them with glass plates. 

Directions (a) (1) What was the action on litmus paper of the solutions of acids studied in Experiment 44 Fill a perfectly dry test tube one-quarter full of glacial acetic acid (this is a pure substance and contains no water) and transfer a drop of it with a rod to a piece of blue litmus paper. (2) How does the result differ from that obtained with the acid solutions in Experiment 44 Add a drop of water to the acid on the litmus paper. (3) What happened (4) What property is exhibited by a solution of acetic acid which is not possessed by the pure substance itself (5) When acetic acid is dissolved in water is any new substance formed (6) What is the evidence (7) Do other acids when dissolved in water form the same substance (8) What is the evidence (9) What is the name of the substance (10) What is its chemical composition (11) How is it essentially different from other substances previously studied (12) Can it be obtained in a pure state out of solution (13) What happens to it when a solution containing it is evaporated (14) What is a test for it ... 

Test a dilute solution of hydrochloric acid with Congo red paper. (1) Tabulate the results of this and the following tests. Test a solution of carbon dioxide in water (carbonic acid) with blue litmus paper and with Congo red paper. (2)... 

Add 5 drops of glacial acetic acid to 10 c.c. of water, and 5 drops of concentrated hydrochloric acid to 10 c.c. of water. Test the two solutions with blue litmus paper and Congo red paper. (5) What are the relative strengths of hydrochloric acid and acetic acid ... 

Aqueous solutions of water-soluble carboxylic acids give an acid test with blue litmus paper. 

The solubility of the compound in water, 5% NaOH, and 5% NaHCOs should be checked (see Chapter 9). Does the water solution turn blue litmus paper red Is there evidence of CO2 evolution when the benzoic acid is added to the bicarbonate solution If positive results are obtained in these tests, how do they confirm that a carboxylic add is present ... 

We have just discussed examples of the sour taste of adds (Sour Patch Kids) and their ability to dissolve metals (spy movies). Acids also turn blue litmus paper red. Litmus paper contains a dye that turns red in addic solutions ( Figure 14.3). In the laboratory, litmus paper is used routinely to test the addity of solutions. Some common acids are listed in Table 14.1. Hydrochloric add is found in most chemistry laboratories. It is used in industry to clean metals, to prepare and process some foods, and to refine metal ores. 

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