But then, if that test can detect poison at 1:50 dilution, it means it probably has enough reagent to detect poison at 1:25 twice, if you're clever about it. Done well, you may end up with a single bottle identified and a bunch of unused tests to sell.

The solution in TFA already requires the test to detect the poinson in a mix of up to 64 bottles as for 7 test each batch will contain half of the (maximum possible 128) bottles.