Book 3 — Testing Direct Current Polarity with Litmus Paper
Reading edition
Litmus paper laid on glass, and moistened with a weak solution of sodium sulphate can be used to test the polarity of a direct current. If the two conductors are touched on the moistened paper, the latter will turn red at the positive, and blue at the negative conductor.
¶A berry stemmer made of a small pair of tweezers is useful for removing superfluous buds from garden flowering plants.