PREFACE.' XI method of feparating argillaceous earth from magnefia, when both are contained in one mineral, which hitherto could not be done without great difficulty, I mean, to any nicety. When both are in a folution of mu riatic acid in a faturated hate, the arsnl- 3 o laceous earth may be perfectly feparated by ammonia faturated with fixed air, as this will only feparate that earth, and the magnefia will be retained in folution; the magnefia may then be feparated, by decompofing the folution after being boiled, with a folution of pure potalh or foda.