The Collaborative International Dictionary
Toluidine \To*lu"i*dine\, n. (Chem.) Any one of three metameric amido derivatives of toluene analogous to aniline, and called respectively orthtoluidine, metatoluidine, and paratoluidine; especially, the commonest one, or paratoluidine, which is obtained as a white crystalline substance.
Note: It is used in the aniline dye industry, and constitutes the essential nucleus or radical of those dyes.
Wiktionary
n. (context organic compound English) Any of the three isomeric aromatic amines derived from toluene; they are used in the synthesis of certain dyes
Wikipedia
There are three isomers of toluidine, which are organic compounds. These isomers are o-toluidine, m-toluidine, and p-toluidine. The o- stands for ortho-, m- stands for meta- , and p- stands for para- . All three are aryl amines whose chemical structures are similar to aniline except that a methyl group is substituted onto the benzene ring. The difference between these three isomers is the position where the methyl group (–CH) is bonded to the ring relative to the amino functional group (–NH); see illustration of the chemical structures below.
Toluidine isomers
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The chemical properties of the toluidines are quite similar to those of aniline, and toluidines have properties in common with other aromatic amines. Due to the amino group bonded to the aromatic ring, the toluidines are weakly basic. The toluidines are poorly soluble in pure water but dissolve well in acidic water due to formation of ammonium salts, as usual for organic amines. ortho- and meta-toluidines are viscous liquids, but para-toluidine is a flaky solid. This difference is related to the fact that the p-toluidine molecules are more symmetrical. p-Toluidine can be obtained from reduction of p-nitrotoluene. p-Toluidine reacts with formaldehyde to form Tröger's base.
Usage examples of "toluidine".
In Preston, England, nobody perceived anything abnormal until it was found that the local atomic-defense chemical plant had substituted toluidine blue for methylene blue.
Out over the sea, he saw, the air was discoloured by the hues of toluidine purple and other chloride chemicals.
You can see the toluidine blue that Krishnamurthi used - there was penetration, or an attempt at penetration.