Mc'W'|';kney — Value of Benzidine for 3Iiiiute Traces of Blood. 217 



Qp-TT (ortho), -which is the 



active body in the well-known test with guaiacum resin and " ozonised ether," 

 " oxydized turpentine," or peroxide of hydrogen solution, associated with the 

 names of Yan Deen and Schoenhein.' Oxidation of guaiacol produces a blue 

 base, probably of the nature of a di-pheno-quinone (cf. the formation of 

 cserulignon, supra). 



The colour formed in the guaiacum test differs from the benzidine colour- 

 base in the same way as a phenol differs from an amine (aniline) or an 

 aurine dye from a rosaniline dye. 



The first writers to draw attention to the behaviour of this class of 

 organic compound with blood were Oskar and Rudolf Adler (3), who found 

 that oxidation of many substances, such as aniline, diphenyl-amine, p. tolui- 

 dine, xylidine, o. m. and p. phenylene-diamine, phenol, o. m. and p. cresol, 

 thymol, pyrocatechin, guaiacol, resorcin, hydroquinone, orcine, pyrogallol, 

 phloroglucinol, salicylic, protocatechuic and gallic acids, henzkUne, tolidiue, 

 a and /3 naphthol, and naphthylamiue, by HjOo, in presence of blood, took place 

 with formation of brilliantly coloured products. They found that the most 

 satisfactory results were obtained from leuco-malachite-green and benzidine. 

 It has been found that ferrous and cui)rous salts, sulphocyanides and 

 oxidative ferments gave similar results. 



My attention was first drawn to benzidine by a paper (4) in the Deutsche 

 med. Wochenschrift, 1906, by Schlesinger and Hoist, of Prof. Strauss's 

 Policlinic in Berlin, who found benzidine a most delicate means of demon- 

 strating minute traces of blood in faecal matter — much more delicate than 

 either of the tests hitherto employed for that purpose in clinical medicine — 

 aloiu and guaiacum. It occurred to me tliat it might prove a valuable means 

 of discriminating blood-stains on clothing, &c. ; and having procured a sample 

 from Merck, and tried numerous experiments with it, I shall now proceed 

 to describe the technique of its use, and the results which I have obtained. 



1. Technique. — An approximately saturated solution of benzidine is made 

 with glacial acetic acid by putting a knife-point full of the crystals into a 

 test-tube, followed by 3 or 4 c.c. of glacial acetic acid, and shaking till 

 solution is effected. Of the clear brownish liquid so produced about ^ c.c. is 

 transferred to a fresh test-tube, and about 2 c.c. HjOs solution (the 20 vol. 

 solution diluted with an equal part of water) added. The whitish opaque 

 mixture is the reagent ; and to it is added tlie material which it is desired to 

 examine for blood, even minute traces of which produce a fine blue colour. 

 The mixture of benzidine and hydrogen peroxide has a strong tendency to 



' According to Doebner and Liicker, the blueing of guaiacum tincture is due to the oxidation of 

 guaiaconic acid CzoHsiiOs. [Archiv f. Fharmalc, ccxwv., 1896, pp. 234, 590.] 



