The tinctorial value of the selenium derivative is further evidenced by the ease with which it forms azo dyes and the deep colors of the latter. This was observed when 6-amino-2-phenylbenzoselenazole was diazotized and coupled with B-naphthol, salicylic acid, etc. The corresponding aminothiazole has been considered difficult to diazotize, on account of its insolubility in hydrochloric acid, cold or hot, but the aminoselenazole dissolves readily and completely, the coupling is almost instantaneous, and the dyes obtained are mostly red and of metallic lustre. In view of the stability of benzoselenazoles toward hot concentrated acids (with the exception of nitric, when nitration ensues) and alkalis, these dyes may prove of some commercial interest. The azole dyes of the benzoselenazole have been exposed to light for weeks, and also exposed to acids and alkalis, and have been found to be quite fast. EXPERIMENTAL Preparation of 2-methyl-4-selenoquinazolone Busch prepared quinazolines by the action of o-amino or o-nitro benzylamine with phosgene, and thioquinazolines with carbon disulphide(51): CH₂NH₂ CH₂-NH / / | C₆H₄ + COCl₂ = C₆H₄ | + 2HCl \ \ | NH₂ NH--CO CH₂NHC₆H₅ CH₂-NC₆H₅ / / | C₆H₄ + CS₂ = C₆H₄ | + H₂S \ \ | NH₂ NH--CS Accordingly the same reaction was tried with o-nitrobenzylamine, prepared by the method of Lellmann and Stickel(50), using carbon diselenide(51). The reaction seemed to work, but the mixture formed was difficult to extract and it appeared that other reactions took place at the same time, due to the impurity of the carbon diselenide, as the latter has never been prepared in the pure state. Another method, which is equally attractive because of its simplicity, is that of Gabriel and Stelzner(52), CHO CH=N / NH₂ / | H₂O C₆H₄ + | = C₆H₄ | + \ H₂N-CO \ | NH₃ NH₂ NH-CO In accordance with the above reaction o-aminobenzaldehyde should work with equal ease with selenocarbamide, but the initial materials were not available. The reaction which was used successfully was that of Bogert, Breneman and Hand(53), NH₂ NHCOR N=CR / / / | C₆H₄ + (RCO)₂O → C₆H₄ → C₆H₄ | \ \ \ | CSNH₂ CS-NH₂ CS-NH ↑ ↑ or