Abstract: Novel squarylium dyestuffs are formed by condensing one molecular equivalent of squaric acid with two molecular equivalents of a heterocyclic intermediate of the formula ##STR1## in which X is an optionally substituted ethylene or o-phenylene group; Y is an optionally substituted methylene or imino group, oxygen, sulfur, selenium or (if X is ethylene) a direct bond; and R.sub.1 through R.sub.5 are various substituents or (except for R.sub.2 and R.sub.5) hydrogen. A preferred class of dyestuffs are those formed from intermediates in which Y is methylene or a direct bond, the former including 7-acylaminotetrahydroquinolines and the latter including 6-acylaminoindolines. Thus, two molecular equivalents of each of 1-methyl-7-acetamido-1,2,3,4-tetrahydroquinoline and 6-acetamido-1,2,3, 3-tetramethylindoline were condensed with one molecular equivalent of squaric acid to produce respective dyes each having an absorption maximum substantially coincident with the ruby-laser wavelength of 694 nm.

Abstract: The present disclosure is directed to novel quenchable, fluorescent dyestuffs which are substantially soluble in low surface tension, substantially non-polar oily solvents, e.g., refined kerosene, and are trisubstituted 4-aminonaphthalimides having the structure formula: ##STR1## wherein R.sub.1 is a member selected from the group consisting of:(a) alkyl groups having from two to twelve carbon atoms,(b) substituted akyl groups having at least two carbon atoms,(c) phenylalkyl groups whose alkyl moiety has from one to four carbon atoms and(d) alicyclic rings having from five to six carbon atoms in the alicyclic ring;R.sub.2 and R.sub.