<prompt> Brain is presented for study in?10 formalin20 formalin30 formalin40 formalin  <response>: Ans. is a i.e. 10 formalin o 10 formalin is used as preservative for histopathological examination of tissue but not used for poisoning or chemical analysis.Preservatives for specific poisons1. Saturated sodium chloride: In all cases of poisoning excluding corrosive acids, except carbolic acids phenol, alkalis, corrosive sublimate and aconite.2. 30 mg potassium oxalate anticoagulant and 10 ml sodium fluoride enzyme inhibitor : Blood in suspected poisoning including alcohol but excluding oxalic acid, ethylene glycol, fluoride, carbon monoxide.3. Rectified spirit : All except in cases of poisoning by : i phenol, phosphorus, paraldehyde, ii kerosene, iii formaldehyde, formic acid, iv alcohol, acetic acid v chloroform, chloral hydrate, vi ether.4. 10 mgml NaK. fluride and 3 mg K-oxalate: For preserving blood; fluride is also added to CSF, vitreous humor; and urine if alcohol estimation is required; and also in analysis of cocaine, cyanide and carbon monoxide.5. 5 wv sodium citrate and 0.25 vv formalin: Blood grouping.6. 30 mg sodium citrate in place of potassium oxalate: Blood in poisoning of oxalic acid and ethylene glycol.7. 10 gm sodium nitrite in place of sodium fluoride: Blood in poisoning by fluoride.8. Heparin and EDTA: Not used as interfere with methanol detection.9. 10 formalin: Histopathological examination of tissue but not used for poisoning or chemical analysis.10. Liquid paraffin : In CO poisoning added immediately over blood to avoid atmospheric O2 exposure.11. Thymol, cone HCL, sodium fluride, saturated saline, rectified sprit, sodium benzoate and toluene : Urine 10 ml.12. 50 glycerine : Specimen for virological examination.13. No preservative: i Bone, hair, nail ii lung for detecting inhaled poison, iii refrigration available 4degC, iv analysis within 24 hours. 