Today I Learned . . .

1. Joni Mitchell wrote the hit Nazareth song "This Flight Tonight".

2. When injecting chemicals into water, sodium hydroxide (NaOH or "caustic") must be injected before sodium hypochlorite (NaOCl or "chlorine"). The reason is, injecting sodium hydroxide into water first, will raise the pH of the water. This will enable more of the free chlorine to persist longer.