Natural soluble solids. The natural total soluble solid content is determined after the chloride content has been determined and added salt has been deducted. For every 1 % chloride, 1,13 degrees Brix or 0,0157 refractive index must be subtracted (at 20 °C). These corrections take account of the pre-existing natural salt content, which is fixed arbitrarily at 2 % of the total solid content.