Some Bemarhahle Oxidation-Products of Bejizidine. 
207 
somewhat fallacious. However, the formula C12H12N2O + f H^CrO^ agrees 
fairly well/requiring C = 49-9, 11 = 4-7, Cr = 13-5, N = 9-7 per cent. The 
supposition indeed might be made that the diimine has four times the 
normal molecular weight, its constituents being so arranged as to give 
only six amino groups, i.e., C^sH^gO^Ns + SH^CrO^. In one preparation, 
however, where dilute hydrochloric and only two molecular proportions of 
K2Cr207 were used, the product contained 17*0 per cent, chromium, in 
agreement with normal diphenoquinonediimine chromate. Again, when a 
fair amount of mineral acid and considerable excess of CrOg are used a 
different substance is obtained. This forms olive-green, practically 
black, felted needles with a faint reddish lustre, and is apparently a 
simple sesquichromate of diphenoquinonediimine. The same substance 
is obtained more certainly by oxidising benzidine in cold hydrochloric 
acid solution with permanganate (about 15 cc. N solution per gram) to 
the deep-orange diimine hydrochloride and then precipitating with CrO^ 
solution. The chromium-content, however, varies between 20 and 24 
per cent. 
A special preparation of this dark substance was made by treating 
benzidine in HCl solution with dilute H2O2 and then with Cr03 in excess 
(H2O2 alone has no action in the cold, though in absence of mineral acid 
a white peroxide of benzidine has been obtained in long white needles). 
The crystalline product had a bronze lustre and contained no chloriue. 
After prolonged drying at 50° C, 04854 gm. gave 0-7220 CO2 and 
0-1887 H2O, also 0-1472 Or203. Kjeldahl nitrogen was 6-1 per cent., 
but the method is probably unsuitable. Found C = 40-6, H = 4-3, 
Cr - 20-7, N - 6-1. C,2H,oN2 + l^K.GiO^ requires C = 40-1, H = 3-6, 
N = 7-8, Cr = 21-7 per cent. The base of this preparation was extracted 
with acetone, precipitated by water, and boiled out with excess of the 
latter to remove a little benzidine. This treatment evidently caused it to 
lose nitrogen, as it melted indistinctly at 190° C. (the diimine melts at about 
270°). It was nevertheless analysed, as it had appeared to be uniform. 
0-2187 gave 0-6917 CO2 and 0-1118 H2O : 0-1351 used 5-62 N/5 acid. 
Found C - 79-9, H = 5-7, N - 11-7 and 12-3 per cent. C,2H,,N2 
requires C = 79-1, H - 5-5, N - 15-4. 
An attempt to synthesise a quinhydronic compound of diphenoquinone 
and benzidine (which would agree with these figures) gave an olive 
crystalline compound which gives an olive to blue coloration with 
H2SO4. The present compound is therefore not a benzidine-quinhydrone. 
Barziloiv sky's "Benzidine Ferricyanide." — Potassium ferricyanide does 
not oxidise benzidine in mineral-acid solution, though it does so in neutral 
or acetic acid solution. The blue product is, however, amorphous. A 
crystalhne preparation is easily obtained by first oxidising with perman- 
ganate and then adding K.Fcy (using acid enough to keep up manganese 
