EARTHS. 261 



(e.) Not volatile by any heat hitherto applied. 

 tf.) Form soaps with oils. 



(g.) In common with the other earths, combine with acids and 

 form salts.* 



EARTH OF A MIXED CHARACTER. NAMELY, MAGNESIA. 



a.} Not acrid or caustic. 



b.) Applied in substance, affects the vegetable colors. 



c.) Nearly insoluble in water, but absorbs it. 



d.) Equally difficult to fuse as lime, not volatile. 



e.) Combines readily with acids to form salts. 



/.) Combines indirectly with oils to form soap. 



EARTHS PROPER. SILICA ALUMINA GLUCINA ZIRCONIA 



YTTRIA.f 



Destitute of alkaline properties, except that 



(.) They unite with acids, and form salts ; silica combines per- 

 manently with only one acid ; i. e. the fluoric. 



b.) Insoluble in water ; but most of them absorb it, 

 c.) Tasteless, innoxious, inodorous. 

 d.) No effect on test colors. 



e.) Very difficult to melt, but less so than the alkaline earths $ 

 still the alkaline earths are powerful fluxes of the earths proper, and 

 of common metallic oxides. 

 (/.) Not volatile by heat. 

 (g.) In their pure state, do not combine with oils to form soap. 



SEC. I. LIME. 



1. DISCOVERY. Familiarly known from the remotest ages. 



2. PREPARATION. 



(a.) By thoroughly igniting, in a good furnace, in a covered crU" 

 cible, small fragments of marble, chalk, J or shells, or other pure cal- 

 careous carbonate of lime, (Carrara and Parian marble are prefer- 

 red,) these substances lose half their weight or more in the form 

 of gas and water, and if fully calcined, they will not effervesce with 

 acids. 



(b.) As the natural carbonates of lime are not always pure, we 

 may dissolve them in dilute muriatic acid ; then add ammonia, which 



* Even silica combines permanently with fluoric acid, and transiently and slightly 

 with some other acids ; this earth differs in several respects from the rest, and some 

 have even regarded it as an acid. 



t It is scarcely necessary to remark that Thorina, which was transiently admit- 

 ted among the earths, has been found to be a sub-phosphate of Yttria. 



t Chalk is the least pure of the three. 



