HILLEBRAND.] ZIRCONIUM. 75 
tip of a Bunsen burner, and then moistening with hydrochloric acid. 
This should bo known to everyone, but probably is not. 
The procedure outlined in the foregoing paragraphs for the estima- 
tion of calcium, strontium, and barium in silicate rocks is the one which 
long experience has shown to be best adapted for securing the most 
satisfactory results with a minimum expenditure of time. 1 Even where 
no attempt is made to separate contaminating traces of SrO and BaO 
one from the other, the error is usually of no great consequence, for 
an absolute error of 25 per cent, even, in a substance constituting only 
one or two tenths per cent of a rock is ordinarily of small moment 
compared with the ability to certify to its presence with approximate 
correctness. 
With such small amounts of barium as are usually found in rocks it 
is doubtful if Mar's 2 method for the separation of barium from calcium 
and magnesium, by the solvent action of concentrated hydrochloric 
acid mixed with 10 per cent of ether on the chlorides, could be con- 
veniently applied here, although for larger amounts the method would 
seem to be accurate and easily executed. Moreover, it would proba- 
bly not entirely remove contaminating strontium, and hence offers no 
advantage. 
XIV. ZIRCONIUM. 
This element is rarely looked for by chemists, though shown by the 
microscope to be one of the most constant rock constituents, usually 
in the form of zircon, in which occurrence its amount can be approxi- 
mately judged of and a chemical test rendered almost unnecessary; but 
sometimes it occurs in other minerals, and is then unrecognizable under 
the microscope. It may rarely be present up to a few tenths of 1 per 
cent of the rock. 
author's method. 
For its detection and estimation in such cases, or whenever a search 
for it seems called for, the following procedure, based on a method 
by G. H. Bailey, 3 has been devised, which serves, when carried out 
with care, to detect with certainty the merest trace — 0.02 per cent, for 
instance — in 1 gram. 
The preliminary treatment of the rock powder has been fully given 
under Barium (p. 74), where the separation from barium has been 
described and also the concentration of the zirconia in a small amount 
of very dilute sulphuric solution. This should probably not con- 
tain much above 1 per cent of sulphuric acid, though the actually 
permissible limit has not been established. To the solution, which 
iFor details consult W. F. Hillebrand: Jour. Am. Cheui. Soc, Vol. XVI, p. 83, 1894; Chemical News. 
Vol. LXIX, p. 147, 1894. 
•Am. Jour. Scl., 3d ser., Vol. XLIII, p. 521, 1892. 
3 Jour. Chem. Soc, Vol. XLIX, pp. 149,481, 1886. 
