For the purposes of heading 4702, the expression “chemical wood pulp, dissolving grades” means chemical wood pulp having by weight and insoluble fraction of 92% or more of soda or sulphate wood pulp or of 88% or more for sulphite wood pulp after one hour in a caustic soda solution containing 18% sodium hydroxide (NaOH) at 20oC, and for sulphite wood pulp an also content that does not exceed 0.15% by weight .