PHYSICAL PROPERTIES OF MINERALS. 129 



the metallic oxides. With the second, we examine whether the fusion 

 of bodies along with it takes place slowly or with rapidity, without ap- 

 parent movement or with effervescence, whether the glass resulting 

 from the fusion acquires color, and whether this color is different in the 

 fire of oxidation from what it is in the fire of reduction ; and finally, we 

 notice whether the discoloration of the borax augments or diminishes by 

 becoming cold, and whether the glass preserves or loses its transparency. 

 The salt of phosphorus is employed particularly in the examination of 

 the metallic oxides, whose characteristic colors it immediately develops: 

 it is also a valuable reagent for the silicates. Charcoal is the support 

 most frequently made use of, when these reagents are employed. In 

 no instance should the quantity employed, of the flux and the mineral 

 together, exceed in size a pepper-corn ; and in those instances where a 

 mineral is used without a flux, it should not exceed, in general, the head 

 of a common sized pin. 



For more complete information upon the use of the Blowpipe, the 

 reader is referred to the excellent treatise of Prof. Berzelius, the first 

 edition of whose work has been translated from the Swedish into both 

 the French and German languages, and the second edition of which was 

 published at Nttrnberg, in 1828. 



Action of Acids. The acids employed most generally are the Nitric, 

 the Muriatic and the Sulphuric. When the two former are used to dis- 

 cover the carbonates of the alkalies, of the earths and the metallic oxides, 

 they are employed in a state of dilution; and the mineral to be examined 

 has a small fragment, the size of a pepper-corn, detached, which, either 

 unbroken or crushed to powder, is put into a wine glass, upon which 

 the acid is affused, when the effervescence from the liberation of the 

 carbonic acid gas becomes apparent. If the trial be to learn whether 

 the acid forms a jelly with the dissolved mineral, (and which never takes 

 place with the carbonates, or those that effervesce,) a stronger acid is 

 employed and a larger quantity of the mineral previously reduced to an 

 impalpable powder; a little heat is also requisite, and considerable time 

 is needed for the digestion of the powder : on cooling, the fluid gelatin- 

 izes. Occasionally, the color of the solution of a mineral in these acids 

 is noticed, with a view to detect their metallic ingredients. The sul- 

 phuric acid is used without dilution, for the purpose of detecting fluoric 

 acid: it is poured upon the mineral in a state of powder, in a glass tube, 

 when the fluoric acid becomes obvious, from the corrosion of the glass, 



