Antiseptic Action and Chemical Constitution. 337 



The hydrochlorides of certain of the compounds require the presence of a 

 slight excess of hydrochloric acid in order to effect solution, e.g., in the case of 

 9.phenylacridine [31] and 2.amino-3.methylnaphthacridine [58] ; but the 

 enhanced effect of the methochlorides [32, 59] over the respective hydro- 

 chlorides [31, 58] is not to be ascribed to the higher hydrogen-ion concen- 

 tration of the solution of the latter, since the addition of hydrochloric 

 acid to the methochloride, so as to produce a solution of similar reaction, did 

 not reduce the antiseptic power to that of the hydrochloride. The com- 

 parative effects of the hydrochloride and the methochloride of the same base 

 in peptone water show a much less regular behaviour. 



The Substitution of other Radicals for the Methyl Group in Diaminoacridine 

 Methochloride. — The following were examined : ethyl [37], propyl [38], n- [39] 

 and iso-butyl [40], iso-amyl [41], phenyl [42], benzyl [43], also the chloro- 

 acetate [44], chloropropionate [45], and chloroacetanilide [46] derivatives. 

 The result was that, within the limits of experimental variation, these com- 

 pounds are practically identical with the methochloride [36] in their 

 antiseptic power for both organisms. 



The Substitution of Alkyls in the Amino Groups. — Tetramethyl- [52] and 

 tetraethyl-diaminoacridine [55] hydrochloride and also the methochlorides 

 [53, 56] and methonitrate [54, 57] were investigated. The tetramethyl hydro- 

 chloride [52], while practically equal to unsubstituted diaminoacridine [35] 

 in its action on Staphylococcus aureus, was distinctly inferior for B. coli, both 

 in peptone water and in serum. The tetraethyl compound [55] was still 

 weaker ; thus with the latter the sterilising concentration for staphylococcus 

 in peptone water was 1 : 100000 and in serum 1 : 10000, while for B. coli a 

 concentration not less than 1 : 1000 was required. The methochloride [53] 

 and methonitrate [54] of the tetramethyl compound were practically equal to 

 the hydrochloride ; also, as in the case of the unsubstituted diaminoacridine, 

 the effect in serum with the hydrochloride and methochloride was practically 

 equal. On the other hand, the methochloride [56] and methonitrate [57] of 

 the tetraethyl compound were much more active in serum than the hydro- 

 chloride. 



Groups which interfere with Antiseptic Action. — As has been shown above, 

 the introduction of methyl and ethyl groups into the amino radicals depresses 

 rather than enhances the antiseptic potency [52, 55, as compared with 35], 

 thus contrasting with the effect of similar substituents in the diamino- and 



atom, thus converting the compound into a quaternary base, should be recalled in this 

 connection ('Trans. Roy. Soc.,' Edinburgh, vol. 25, pp. 151,693 (1868-69); 'Proc. Roy. 

 Soc.,' Edinburgh, vol. 6, p. 556 (1868-69)). It has been shown, however, by Lenz that 

 diaminoacridine methochloride is totally devoid of curare action, either in cold or warm 

 blooded animals (' Zeitschr. f. d. gesamt. experim. Med.,' vol. 12, p. 195 (1921)). 

 VOL. XCIII. — B. 2 B 



