Replace absorption tube before it becomes exhausted. Protect them by attaching a tube of CO2-absorbing granular material such as soda lime or a commercially available CO2-removing agent.* Use at least 70 cm of rubber tubing to minimize vapor diffusion from bottle. Store NaOH solutions in polyethylene (rigid, heavy-type) bottles with polyethylene screw caps, paraffin-coated bottles with rubber or neoprene stoppers, or borosilicate-glass bottles with rubber or neoprene stoppers. Alternatively prepare dilute solutions by dissolving the weight of solid NaOH indicated in Table B in CO2-free distilled water and diluting to 1000 mL. Use the supernate for preparing dilute solutions listed in Table B. Remove sodium carbonate precipitate by keeping solution at the boiling point for a few hours in a hot water bath or by letting particles settle for at least 48 h in an alkali-resistant container (wax-lined or polyethylene) protected from atmospheric CO2 with a soda lime tube. Stock sodium hydroxide, NaOH, 15N (for preparing 6N, 1N, and 0.1N solutions): Cautiously dissolve 625 g solid NaOH in 800 mL distilled water to form 1 L of solution. See Table A for preparation of HCl, H2SO4, and HNO3 solutions.Ī. Prepare the following reagents by cautiously adding required amount of concentrated acids, with mixing, to designated volume of proper type of distilled water. Preparation of Common Types of Desk Reagents Specified in Standard Methods Acid Solutions
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