258. Dilute sulphuric acid, for these experiments, should be made by mixing 1 part, by volume, of concentrated acid, with 20 parts of water. Do not let the acid get upon clothes or carpets. Do not add water to acid. Mix by slowly adding the acid to the water in a glass or earthen dish, stirring at the same time. Mix over a sink or out of doors. (For fuller details see App. Book; § 21, 22, 23, 24, 25.) To save time, make at least a quart of the mixture, bottle, and label it for use.
259. Directions. (A) Bend over one end of each of the wires and metal strips, and hang them upon the edge of the tumbler ([Fig. 81]), so that their lower ends shall be in the acid. Do not let them touch each other. Stand the carbon rod in the acid.
If there is no visible action upon any of the above substances, add a few drops of concentrated acid to the tumbler.
Note carefully what takes place in the tumbler, and state which of the substances are dissolved, which simply made brighter, and which not acted upon at all.
260. Discussion. The bubbles of gas that arise from the zinc when it dissolves are hydrogen, and they indicate that a vigorous chemical action is going on in the tumbler, and that the zinc is being eaten away.
EXPERIMENT 109. To study the effect of dilute sulphuric acid upon various combinations of metals.