%thale%

n. a type of large-holed Swiss cheese.
Syn. -- Emmenthal, Emmental, Emmenthaler. [ WordNet 1.5 ]

n. (Chem.) A white crystalline aromatic hydrocarbon, C10H8, analogous to benzene, and obtained by the distillation of certain bituminous materials, such as the heavy oil of coal tar. It is the type and basis of a large number of derivatives among organic compounds. Formerly called also naphthaline. [ 1913 Webster ]

Naphthalene red (Chem.), a dyestuff obtained from certain diazo derivatives of naphthylamine, and called also magdala red. --
Naphthalene yellow (Chem.), a yellow dyestuff obtained from certain nitro derivatives of naphthol. [ 1913 Webster ]

a. (Chem.) Pertaining to , or derived from, naphthalene; -- used specifically to designate a yellow crystalline substance, called naphthalenic acid and also hydroxy quinone, and obtained from certain derivatives of naphthol. [ 1913 Webster ]

n. [ Pref. para- + naphthalene. ] (Chem.) Anthracene; -- called also paranaphthaline. [ Obs. ] [ 1913 Webster ]

or ., n. (Chem.) A white or yellowish white crystalline substance, C20H14O4, formed by condensation of the anhydride of phthalic acid and phenol. Its solution in alkalies is brilliant red, but is decolorized by acids. This reaction, being very delicate, is used as a pH indicator. It is sometimes used as a laxative in veterinary medicine. [ Webster 1913 Suppl. +PJC ]

n. [ See Phthalic. ] (Chem.) One of a series of artificial organic dyes made as condensation products of the phenols with phthalic acid, and well represented by phenolphthalein. Their alkaline solutions are fluorescent. [ 1913 Webster ]

Phenol phthalein, a white or yellowish white crystalline substance made from phthalic acid and phenol. Same as phenolphthalein. [ 1913 Webster + PJC ]