OP ARTS AND SCIENCES. 109 



III. IV. 



27.08 



40.33 



Considering the ease with which the substance is decomposed, the 

 agreement between these results and those calculated from the formula 

 is as close as can be expected. The method of puritication described 

 above, however, does not always give such satisfactory results. Sam- 

 ples from two other preparations gave numbers which differed by about 

 one per cent from those corresponding to the formula, the chlorine 

 being too low and the other constituents too high by this amount ; but we 

 ascribe this to partial decomposition of the substance during the purifi- 

 cation, as both of these specimens were much darker in color than that 

 which gave the more satisfactory analyses. The objection which might 

 be founded on these results, that our substance was not a definite com- 

 pound, but a mixture of ammonic chloride with some organic body less 

 rich in nitrogen than the chloride of pentamidobenzol, is removed by 

 the microscopic examination of the substance, which showed that it 

 consisted of well developed rhombic crystals without any admixture 

 whatever, to which may be added the fact that chlorplatinic acid gave 

 no precipitate with a solution of the substance. 



Properties. — The trichloride of pentamidobenzol, as precipitated by 

 hydrochloric acid from its aqueous solution, is seen under the micro- 

 scope to consist of rather thick well developed transparent rhombic 

 plates, with the sharper angles truncated by a single plane. It is color- 

 less when first prepared, but soon turns pink or gray, and on long 

 standing passes through dark brown to black, a change which is much 

 accelerated by heat ; yet even after it has become nearly black, if ex- 

 amined with the microscope, it is found to retain unaltered its crystal- 

 lii.e form, and the individual crystals are still transparent, although 

 very much darkened, so that this change in color seems to have taken 

 place only superficially. It is very easily soluble in water, but only 

 slightly soluble in strong hydrochloric acid, a property which is useful 

 in the purification of the substance. Tiie aqueou-i solution decomposes 

 quickly when heated, a black tar being formed, and a similar change 

 takes place more slowly at ordinary temperatures, the solution becom- 

 ing at first clear pink, and then darkening through shades of red to 

 black. The action of more violent oxidizing agents is described below, 

 and resembles that of the air. . The salt when dry or moistened with 



