Wash the oranges and cut each orange into about 8 segments, leaving the peel on. Cover with water, add bicarbonate of soda, bring to the boil and simmer for 20 minutes. Tie the spices in a piece of muslin, put in a saucepan with the vinegar, cover and simmer for about 20 minutes. When the orange peel is soft, drain off water. Remove the spice bag from the vinegar. Add sugar and keep over a low heat until the sugar has dissolved. Bring to the boil, add the orange segments and simmer, covered, for a further 20 minutes. Remove the orange segments with a draining spoon and pack into jars. Boil the vinegar and sugar until the consistency of thin syrup and pour over the oranges. Seal.