INSTRUMENTS AM) < 111 MK'AI. TI.STS :>i\7 



Illustration. Heat a small fragment of calcite, < n the 



o. K. ; at Mr>t there will be no flame (x^oration, but as tiie fragment 



beci Hues incande.-cent a \-rry delicately colored llainr will appear. 

 After cooling, moisten the same fragment with IK'l and heat 

 again; the yellowish red flame of calcium will at once appear. 

 Place the ignited fragment on turmeric paper and moi-ten with a 

 drop of water; the paper will show the alkaline reaction. 



Radium, Ka. Atomic weight, 226.4. 



Radium is not contained in any mineral in amounts sufficiently 

 large to yield blowpipe tests. In its chemical properties it is like 

 barium, and may be concentrated and separated with barium, from 

 which it is separated by fractional crystallization. It differs from 

 barium in yielding a crimson flame. 



Magnesium, Mg. Atomic weight, 24.32. Fusing point, 632.6 C. 



a. Cobalt solution affords the only blowpipe test for magnesium. 

 A large number of light-colored minerals containing magnesium 

 become pink or flesh-colored after ignition with cobalt solution. 

 This test at best is not very satisfactory, and especially as it cannot 

 be applied to minerals dark in color, or those which become dark 

 upon ignition. 



6. Alkaline test. Some minerals containing magnesium when 

 strongly ignited and placed on turmeric paper will yield the alkaline 

 reaction. In most cases the reaction is not very marked ; the frag- 

 ment must be allowed to rest on the paper for several minutes, and 

 even then the alkaline reaction may be found only directly under 

 the fragment. 



c. Wet test. Magnesium is a component of a large number of 

 silicates and other difficultly soluble minerals, in which it is asso- 

 ciated with iron, aluminium, calcium, etc., and from which the 

 magnesium must be separated before the wet test can be applied. 



The insoluble mineral is finely powdered and fused either on wire 

 or platinum foil with four parts of soda ; the fusion is dissolved in 

 dilute HC1, and evaporated in a small porcelain dish to dry ness on 

 the bath. The dry residue is moistened with HC1, then dilute with 

 5 cc. of water ; stir and let stand on the bath for a minute or so. 

 The residue remaining insoluble will be silica, and is filtered out ; 

 the filtrate is collected in a test tube, boiled with 3 or 4 drops of 

 nitric acid to oxidize the iron to ferric iron ; 3 drops of concen- 

 1 rated HCl are now added, the solution shaken and nentrali/ed 

 with ammonia, when iron and aluminium are precipitated as hy- 

 droxides ; after filtering, the filtrate, containing the magnesium 



