Sudstituted the abstract with a new abstract as follows: The invention
relates to a continuous process for separation a mixture of hydrocarbons
which has beenobtained by extractive distillation of C.sub.4 fraction
useing a selective solvent and the hydrocarbons from the fraction C.sub.4
which are more readily soluble in the selective solvent than are the
butanes and the butenes. The mixture is fed into a first distillation
column in which it is separated into a steam which is taken off at the
top and comprises 1,3-butadiene, propyne, possibly further low boilers
and possibly water and a bottom stream comprising 1,3-butadiene,
1,2-butadiene, acetylenes and possibly further high boilers, with the
proportion of 1,3-butadiene in the bottom stream from the distillatin
column being regulated in such a way that it is at least sufficiently
high to dilute the acetylenes to outside the range in which there is a
risk of spontaneous decomposition. The stream taken off from the top of
the first distillation column is fed to a second distillation column and
is separated into a steam which is taken off at the top and comprises
propyne, possibly further low boilers and possibly water and a bottom
stream comprising pure 1,3-butadiene in the second distillation column.