What precautions should be taken when preparing a concentrated solution of sodium hydroxide?
I do not need to tell you to wear spex and a lab coat. Take
The dissolution of caustic soda is quite exothermic, and the mix might spit at you, so safety spectacles to protect your mince pies, and a lab coat to protect your clothes are absolute requirements.
Once the initial reaction is over, the volume can be made up to
Note also that base burns are quite insidious. You get splashed by an acid, it stings, and you wash it off pdq. Get splashed by base and it does not sting: it still does damage, but the soapy, slimy nature of bases means that you might not notice the burn, until it has done some damage.