Meaning of リトマス紙 in Japanese

When investigating the pH (acidic, neutral, alkaline) of a liquid, don't soak the litmus paper completely in the liquid but just put the end of the paper in it.

It came in a handsome wooden box and contained a rack for test tubes, glass bottles of powerful powders, a little packet of sensitive paper (litmus, I think), a glass rod, the manual and suitably exciting poison labels.