I Elements of Mineralogy. 3 Moft earths are foluble in fome acid or other, and many in all acids; the Pruffian alkali can precipitate none of them from thefe folu- tions; whereas, it precipitates all metallic fub- llances from their acid folvents *. This forms a diflinä: line of feparation betwecn earths and metallic fubftances. The exception, formerly made in favour of barytic earth, is now found to have arifen from a miftake. * Except Platina.