Safe concentration of HCl for Year 8 students to use?: A year 8 textbook has an activity which includes an example for a colour change (blue litmus paper with HCl added to it).

Safe concentration of HCl for Year 8 students to use?: A year 8 textbook has an activity which includes an example for a colour change (blue litmus paper with HCl added to it).
Risk assessment (thiosulfate): Do you have a RA for the reaction of 0.1M sodium thiosulfate with 2M hydrochloric acid, especially the cleaning up and disposal.
Sulfur disposal: Could you please advise on the procedure for disposing of sulfur, specifically sulfur mixed with iron filings and HCl.