BLOWPIPE REACTIONS. 87 
are the carbonates, sulphates, nitrates, and chlorides of the 
alkaline metals. 
Testing for Alumina or Magnesia,.—Cobalt nitrate, in solu- 
tion, is used to distinguish an infusible and colorless mineral 
containing aluminium from one containing magnesium. <A 
- fragment of the mineral is first ignited, and then wet with a 
drop or two of the cobalt solution and heated again. The alv- 
minium mineral will assume a blue color, and the magnesium 
mineral a pale red or pink. 
Any fusible silicate, when moistened with cobalt nitrate and 
ignited will assume a blue color, hence this test is only deci- 
sive 1n testing infusible substances. 
Infusible zinc compounds, when moistened with cobalt nitrate, 
assume a green color. 
Testing for Lithium.—Some lithium minerals give the 
bright purple-red flame if simply heated in the platinum for- 
ceps. In other cases mix the powdered mineral with one part 
of fluorite and one of potassium bi-sulphate. Make the whole 
in‘o a paste with a little water, and heat it on the platinum 
wire in the blue flame. 
Testing for Boron.—When the bright yellow-green of boron 
is not obtained directly on heating the mineral containing it, 
one part of the powdered mineral should be mixed with one 
part of powdered fluorite and three of potassium bi-sulphate ; 
and then treated as in the last. The green color appears at the 
instant of fusion. 
Testing for Fluorine.—To detect fluorine in fluorides mix a 
little of the powdered substance with potassium bi-sulphate, 
put the mixture in a closed glass tube and fuse gently. The 
bi-sulphate gives off half of its sulphuric acid at a high temper- 
ature, which acts powerfully on anything it can attack. IRfa 
fluoride is present, hydrofluoric acid will be given off, and the 
walls of the tube wili be found roughened and etched when the 
tube is broken open and cleaned after the experiment. Ifa 
silicate containing fluorine be powdered and mixed with previ- 
ously fused salt of phosphorus, and heated in the open tube by 
blowing the flame into the lower end of the tube, hydrofluoric 
acid is given off, and the tube is corroded just above the assay. 
Silicates.—Nearly all silicates undergo decomposition with 
salt of phosphorus, setting free the silica, forming a bead which 
is Glear while hot and has a skeleton of silica floating in it. 
The bead is sometimes clear also when cold. 
Jron.—Minerals containing much iron produce a magnetic 
globule when highly heated. Usually the reducing flame is 
