METHODS OF TESTING. 29 



Moisten the loop, and dip it into either borax or * micro- 

 cosmic salt ; then heat it in the blowpipe flame till the flux 

 is fused. When the head is soft or moist, it must be brought 

 in contact with a very small quantity of the powdered mi- 

 neral, and then exposed to the heat of the oxidizing flame, 

 and afterwards to that of the reducing flame, the change of 

 colour of the head when hot or cold, and the effect of each 

 flame on it, being carefully observed. 



If the substance, after heating, be moistened with nitrate 

 of cobalt solution, and again strongly heated, it may when 

 cool afford some clue to its nature (see Table C). 



This reagent is often used for detecting 

 ( magnesia, which gives a pale red colour ; 

 \ alumina, blue without lustre. 



GENERAL TABLE 0. 



(For the Analysis of Metallic Substances.) 



1 . Heat the substance in a tube closed at one end : 



Sublimate : white = mercurous chloride, white antimony, &c. 

 ,, greyish black = mercury, &c. 



black, red, on rubbing = cinnabar (sulphide ol 



mercury). 

 black when hot ; red, cold = antimony sulphide. 



Arsenical minerals, too, afford a sublimate. 



2. In open tube : 



Sublimate : metallic globules = mercury. 

 ,, white fumes = antimony. 



3. Alone on charcoal : 



Colour of outer name : green = copper, &c. 



blue = lead, chloride of copper, &c. 

 (i.) Metals reduced without incrustation : 



White, maUeable bright bead = silver. 



YeUow = gold. 



Red metal = copper. 



Grey powder = iron, cobalt, nickel, 



platinum. 

 (5i.) Metals reduced with incrustation : 



Incrustations : lemon yellow when hot ) _i ea j \ 



sulphur yellow when cold \ ~ ' ' f malleable 

 yellowish when hot \-tin ( metal, 

 white when cold ] ' ) 



orange, when hot \ =bis- \ 



lemon yellow when cold } muth. f brittle 

 white (fumes given off \ =anti- I metal, 

 on withdrawal of flame) } mony. / 



* N.B. Microcosmic salt is inclined to froth up and fall off the 

 wire ; eo only a very small quantity must be taken up at once. 



