Which of the following is not used as a preservative in chemical analysis

Formalin is not used as preservative for chemical analysis because extraction of poison becomes diffcult. Preservatives:- * Saturated sodium chloride solution * Rectified spirit * 10 mg/ml of sodium or potassium fluoride for blood, urine, CSF * Glycerol is used for virological study. Ref:- Essentials of Forensic medicine, Dr KS narayana Reddy 33th Edition; Pg num:- 124