TRANSFORMATION OF NITROAMINES AND ALLIED SUBSTANCES. 123 
without a still-head of a mixture containing only 10 per cent. of acetic 
acid will give but some 8 to 10 per cent. of pure anhydride. By use of 
Young’s ‘ pear’ still-head the pure substance, amounting to 50 to 60 per 
cent. of the original material, can be readily obtained. Its physical con- 
stants differ materially from those usually given; Landolt’s values 
alone agree with ours. The boiling point is 1389°55° under 760 mm. 
pressure, and the density 10876 at 15°/4°, and 1:082 at 20°/4°. The 
refractive index for H® at 15° is 1°39069. At 15° about 2°7 grams 
of water dissolve in 100 grams of acetic. anhydride, and 12 grams of 
anhydride in 100 grams of water. 
Action of Halogens on Acetic Anhydride.—When light is excluded 
solutions of chlorine and bromine in acetic anhydride are quite stable. 
But in the presence of strong acids, iodine, ferric chloride, &c., a very 
rapid reaction follows. 
TABLE Y. 
H,SO04 = 17/3000 I = 1/300 FeCl; = 1/535 
Time Titre of 5ce.c.in | Time Titre of 5c.c. in Time | Titre of 5c.e. in | 
(Min.)|} 2/50 Thiosulphate | (Min.)) 2/50 Thiosulphate |(Min.)| 1/50 Thiosulphate | 
C.c, C.C. C.c. 
0 12°4 0 9°4 0 10°7 
36 7°35 5 9-1 8 8°7 
75 4-1 45 2°05 12°5 72 
112 2°5 34 0-1 
The catalysts are effective as the first power of their concentration ; 
when acids can be compared—for example, sulphuric and perchloric— 
it is found that molecular and not equivalent quantities are equally 
effective. 
The fall in titre of the bromine is independent of the initial concen- 
tration of the solution, and hence bears a linear relation to the time, 
that is, the graph of da/dt is a straight line. Lapworth accounted for 
an exactly similar relation in the attack of bromine on acetone by sup- 
posing that the bromine only reacts with a tautomeride of acetone, the 
production of which from the acetone is far slower than its reaction with 
bromine. The rate of disappearance of the bromine is dependent, there- 
fore, only on the formation of the tautomeride, and independent of the 
concentration of the bromine. In the case of acetic anhydride the re- 
active material is only formed in the presence of the catalyst. Hence the 
speed of the bromination, which is proportional to the concentration of 
the former, must obviously also be proportional to that of the catalyst. 
There is no such detectable acceleration of the action of bromine on 
acetic acid by acids (except possibly when their concentration is very 
high); hence it may be deduced, a similar reactive substance is not: pro- 
duced, at least to a proportionate extent, from acetic acid under the 
influence of acids. 
