Which word in the passage is the adjectival form of 'tolerate'?
Consider line 5, "In the case of wounds, a few leaves can be boiled in water and then this water, when at a tolerable temperature, can be used to wash the wounds."
Here, the word 'tolerable' tells something more about the noun 'temperature', i.e. the temperature is such that you can tolerate it.
Thus, as the word 'tolerable' is an adjective whose meaning is similar in nature to tolerate, it is the adjectival form of the noun 'tolerate'.