Ann: Breakthrough in REE Metallurgy at Caralue Bluff, page-11

This is an leach test to see how much REE can be extracted using a solution. In this case its an acid solution (HCL acid)
Basically, The less acid used, the better the process (ie: cheaper)

20% HCL solution for 4 hours, and 86% recoveries is a very good start.
Interesting to note that 30% HCl solution resulted is LESS recoveries - thats good

now its a matter of refining the leach to try and get better recoveries.

Also to try different solutions to lower the amount of acid used.
Hydrochloric acid is a solution of hydrogen chloride in water.
they mention next step is to try table salt water solution. Salt is Sodium Chloride (NaCl). If that works then Very happy days