3-Calculate the concentration of NaCl required to make an ophthalmic solution containing 20 ml of 1.5 % boric acid & 0.15% atropine sulphate, isotonic with lachrymal fluid. Nacl equivalent of boric acid = 0.50 Nacl equivalent of atropine = 0.12 %3D %3D 4- Calculate the amount of sodium chloride required to make an ophthalmic solution of 1% ephedrine sulphate & 1.2 % boric acid, isotonic with lachrymal fluid. Nacl equivalent of ephedrine sulphate is 0.23 NaCl equivalent of boric acid 0.50 %3D