Sentence:  As <WSD>thymotic</WSD> acid is extremely difficult to obtain, it was found advisable to follow the method of Claus and Krause (J. p. Chem., 1891, [ii], 43, 347), and to prepare 2-bromothymol by decomposing 2-bromothymol-6-sulphonic acid with hydrochloric acid in a sealed tube ... 
Meaning of the word marked with <WSD> tags:  Of, related to, or derived from thymotic acid or thymol.