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Test Papers (Chemistry are made by dipping)

in chemistry, are made by dipping unsized paper into an alcoholic solution of a vegetable coloring matter which changes color when exposed to the action of an acid or alkaline solution. The paper, after being gently dried, is cut into slips of a suitable size.

Hence, by dipping the appropriate test papers into any solution, one can ascertain whether it is acid, alkaline, or neutral. Litmus and turmeric are most commonly used as the coloring matters; litmus for the detection of acids, and turmeric for that of alkalies. Test papers are also employed for detecting sulphuretted hydrogen, etc., and for such a purpose the paper must be dipped in the solution of an appropriate substance.

Thus acetate of lead paper becomes black' in presence of sulphuretted hydrogen, while starch paper becomes blue when touched with iodine.

TESTUDINARIA (so named from the resemblance which the great, rugged, cracked root of the plant bears to the shell of a tortoise), in botany, the elephant's foot or Hottentot's bread; a ge- nus of Dioscoreacex, akin to Dioscorea, but with the seeds winged only at the tip, instead of all round. Rootstock above ground sometimes four feet in diameter.

Stems occasionally 40 feet long; flowers small, greenish-yellow. T. elephantipes Dioscoreaceæ, akin to Dioscorea, is the common elephant's foot or Hottentot's bread. The rootstock is a large, fleshy mass, covered with a thick bark, cracked deeply in every direction. The Hottentots in time of scarcity made use of the fleshy inside of the root as a kind of yam.