shí ruǐ shì zhǐ
(chemistry) litmus paper
石
shí
abbr. for Shijiazhuang 石家莊|石家庄[Shi2 jia1 zhuang1], the capital of Hebei
蕊
ruǐ
variant of 蕊[rui3]
试
shì
to test
纸
zhǐ
paper (CL:張|张[zhang1],沓[da2])