A chemist of an analytic laboratory has to prepare turbidity standards according to the requirements of Pharmacopoeia. What substances are to be used as the reference?

Answer options

1. Furacilinum and calcium chloride
2. Sodium chloride and calcium nitrate
3. Calcium sulphate and glycerin
4. Hexamethylenetetramine and hydrazine sulphate
5. Potassium chloride and barium sulphate