Maximum number of DS18B20 on one pin

Every device that comes from their factory allegedly has a unique 48 bit ID

You could just run the example in the ONEWIRE library and capture the serial monitor output of all your 64-bit ROM addresses (8 BYTES x 8 bits/byte = 64 bits. page one of datasheet

Each Device has a Unique 64-Bit Serial Code Stored in an On-Board ROM

Once you have the terminal capture file with the addresses then just follow the instructions (or examples) in this post..

http://forum.arduino.cc/index.php?topic=239393.new;topicseen#new