Riddles, brain puzzles and mathematical problems

[MyRedNeptune]

A mad scientist has 1000 bottles of a new medicine, but one of them is poisoned. The poison exhibits no symptoms until death. Death occurs within ten to twenty hours after consuming even the minutest amount of poison. In just under 24 hours the king and the rest of the citizens, who are ill, are going to try the medicine. Therefore he must find the poisoned bottle and remove it until then. He has 1000 rats at his disposal which can be used to test the bottles (unfortunately this will probably result in their death if they drink the poison). What is the minimum ammount of rats required in order for the mad scientist to make it on time?

Can I split one bottle into several (please)?