Why 25RPM is mandatory for every tablets in friability apparatus.
This is just to standardize the test conditions of number of rotations. This is to simulate the rattling of tablets during handling in production and further.
Its 25 RPM for 4 minutes or total of 100 rounds at 25 RPM. Which is recommended in pharmacopoeias. Friability is required to check the brackability loss during transportation of uncoated tablets.
This is pharmacopoeial specification