Take a bowl and add citric acid and salt.
Add water and give them a good mix.
Then add rice flour and semolina.
Mix well leaving no lumps behind.
Leave for rest for about 15 minutes.
In the meantime, grease the idli moulds with oil.
Also put the water in a steamer to boil.
When 15 minutes are over, give one more mix to the batter.
Divide the batter into two parts.
Note : Actually it's a stage to add baking soda in batter but once baking soda is added, batter needs to be steamed immediately. Our idli mould can make only 8 idlis at a time whereas the batter is of 16 idlis, so this is the reason to divide the batter. You can act accordingly as per your idli mould.
Add 1/8 tsp of baking soda in one part.
Mix well.
Pour the batter in idli moulds.
Put into the steamer.
Steam for 15 minutes.
Check by inserting the toothpick. If it comes out clean, its a sign that idli is perfectly cooked.
Let it cool a bit for 3-4 minutes.
Take the idlis out using the wet back side of the spoon.
Time to prepare 2nd batch. Add 1/8 tsp of baking soda in rest of the batter.
Prepare the idlis likewise.