The material below is Open Game Content from a 3PP Source
Concentrate poison: The alchemist can combine two doses of the same poison to increase their effects. This requires two doses of the poison and 1 minute of concentration. When completed, the alchemist has one dose of poison. The poison's frequency is extended by 50% and the save DC increases by +2. This poison must be used within 1 hour of its creation or it is ruined.