Soak them in plenty of water for 12-24 hours. Drain, place in a large pot and cover with fresh water, add one tablespoon bicarbonate of soda, bring to a boil, and cook, covered, until soft. It will take at least one hour, but this might vary depending on the size and age of the pulses. But keep in mind that chickpeas needed for hummus need to be super soft, better overcooked than undercooked. To get 9 oz (250 g) cooked chickpeas, you will have to cook about 4.5 oz (125 g) pulses.