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be sure that it is greatly diluted. Keep it in the mouth long enough to determine the taste definitely; then reject it.

b. By means of the stirring rod - it must be washed after every test bring a drop of the dilute acid of a upon red and blue litmus papers. Results? A solution which turns neutral or blue litmus red is said to have an acid reaction. To the dilute acid add a drop of phenolphthalein solution. Result?

Note. - Litmus paper should not be wasted. One piece will do for many tests, if you use only a drop of the liquid each time. A new place on the litmus paper must, of course, be used at every trial. To avoid mistakes by reason of substances which may have spilled upon the table, lay the litmus paper upon the bottom of a clean, inverted beaker.

c. Try the same experiments as in a and b with nitric acid. Results? With tartaric acid. In the case of the tartaric acid use the solution obtained by heating a small crystal with 5 c.c. water. Results?

d. From Experiment XXII, i, tell what happens when iron is treated with hydrochloric acid. Gaseous product? Write the equation here.

From Experiment VIII tell what products are formed from zinc and dilute sulphuric acid. Write the equation. From Experiment X tell what products are formed from magnesium and dilute sulphuric acid. If magnesium sulphate is MgSO4, write the equation.

e. What seems to be the common gaseous product formed when metals act upon acids?

Materials. Solid sodium hydroxide, potassium hydroxide, and calcium hydroxide, ammonium hydroxide solution, litmus, filter paper, phenolphthalein solution.

a. Dissolve a small piece of sodium hydroxide, NaOH, in 10 c.c. water. Rub a drop of the solution between the fingers. Result? Dilute 3 drops of this with 5 c.c. water and taste the solution, using a stirring rod.

Result? Find its effect upon blue and red litmus as in Experiment XXIV, b. Result? Add a drop of phenolphthalein to it. Result? A solution which turns neutral or red litmus blue has an alkaline reaction.

b. Repeat a, using potassium hydroxide instead of sodium hydroxide. Results?

c. Add 2 drops of ammonium hydroxide solution, NH4OH, to 5 c.c. water. Note taste of dilute solution and its action on blue and red litmus and phenolphthalein.

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d. Treat about 1 gram calcium hydroxide, Ca(OH)2, or calcium oxide, CaO, with 10 c.c. water, stir one minute, and then filter. Examine the solution it is called lime-water as to taste, feel, and action upon blue and red litmus and phenolphthalein.

Materials. Sodium chloride, ammonium nitrate, potassium sulphate, sodium acetate, sodium carbonate, disodium hydrogen phosphate, phenolphthalein solution.

a. Treat about one cubic centimeter of sodium chloride, NaCl, in a test tube with 5 c.c. water. Test the solution with blue and red litmus as in Experiment XXIV, a and b. Results? Test it with phenolphthalein. Result?

b. Repeat a with ammonium nitrate, NH4NO3; with potassium sulphate, K2SO4; K2SO4; with with sodium acetate, NaC2H3O2. Results?

c. Repeat a, using sodium carbonate, Na2CO3; disodium hydrogen phosphate, Na2HPO4.

d. Arrange in a table the reactions of the substances you have examined with litmus in Experiments XXII, XXIV, XXV, and XXVI, thus:

What element is found in every acid? What two elements are found in every basic hydroxide? What element is not present, usually, in the salts, i. e., the substances studied in this experiment?

EXPERIMENT XXVII.

NEUTRALIZATION.

Apparatus. - Evaporating dish, stirring rod, wire gauze, ring stand.

Materials. Litmus solution and paper, sodium hydroxide solution, dilute hydrochloric and nitric acids.

a. To 5 c.c. ten per cent sodium hydroxide solution in an evaporating dish add 1 c.c. litmus solution; then add slowly dilute hydrochloric acid until the litmus changes color.

During the addition of acid, stir constantly with a glass stirring rod. If you get too much acid, add sodium hydroxide by means of the stirring rod until the color just becomes blue again; then add a small drop of very dilute hydrochloric acid. With care you can get the litmus to assume a color intermediate between the red and the blue, viz.: a decided lavender. This is the color of neutral litmus, and its formation shows that the basic properties of the sodium hydroxide solution have been neutralized by the hydrochloric acid.

b. Put a drop of the solution upon red litmus, as in Experiment XXIV, b; upon blue litmus. Result?

c. Evaporate the solution carefully. At the end, when

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the water is nearly all off and spattering begins, heat with a small flame in constant motion.

d. Examine the product obtained in c, noting its taste, solubility in water, and the reaction of the solution with litmus. Results?

The substance obtained is sodium chloride, or common salt. Complete the equation, NaOH+HCl →→→→ ? + ? e. Repeat a, b, c, and d, using dilute nitric acid instead of hydrochloric acid. Results?

If the product has the formula NaNO3, complete the equation,

NaOH+HNO3 →→→→? +?

EXPERIMENT XXVIII.

NORMAL AND ACID SALTS.

Apparatus. Two evaporating dishes, burette, test tube, rubber band, filter paper.

Materials. - Pure concentrated sulphuric acid, ten per cent potassium hydroxide solution, phenolphthalein.

a. Put a small rubber band evenly around a test tube to mark off 5 c.c. (see Experiment I). Do not change the position of the rubber during the experiment.

b. Dilute 15 c.c. pure concentrated sulphuric acid by pouring it into 35 c.c. water; stir the mixture with a glass rod, and cool it as in Experiment XXII, b.

Hold your marked test tube vertically and pour in the dilute acid up to the mark. See that the upper edge of the rubber is just at the lower level of the meniscus, i. e.,