Definition of "locked up" on MSDS: I am in the process of rearranging our chemical storage area.

Definition of "locked up" on MSDS: I am in the process of rearranging our chemical storage area.
Bonding and conductivity: Our Year 11s had an electrical conductivity practical demonstrated to them, and the molten silver nitrate did not register a charge on the ammeter.
Precipitation reaction (sodium hydroxide and barium nitrate): I wonder if you can help me out with another confusing chemical reaction we have observed in our lab.
PPE - using gloves with 0.5 M Sodium hydroxide.
This Standard Operating Procedure (SOP) contains a detailed method for preparing sodium hydroxide solutions.