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edited by
Roo O'CONNOR Texas University station, Tx 77843
Hard Rock H. I. Feinstein' George Mason University Fairfax. VA 22030
Under certain circumstances a simple density determination could obviate the necessity of a difficult chemical analysis or a tedious separation of the ingredients of a binary mixture. The method was used by van Hevesy2 to determine the percentages of zirconium dioxide (ZrOz) and hafnium dioxide
' Present address: 10411 Forest Avenue, Fairfax, VA 22030
von Hevesy. George and Berglund. Viggo, J. Chem. Soc (London).
125, 2372 (1924).
(HF02) in the mixed oxides obtained on ignition of the mixed sulfates. It especially applicable to a mixture (not a solution) such as that which occurs in a rock in which the constituents have fairly different densities. A rock has examined petrographically and found to consist of quartz (SiO2) and zircon (ZrSi04)only. The average density of the rock was 3.00 g cm-? The densities of pure quartz and ~ 4.50 g cm-" respectively. pure zircon are 2.65 g ~ r n -and Calculate the percentages by mass and by volume of quartz and zircon in the rock. (Assume the absence of voids in the rock.)
Answers By mass: 71.6%quartz; 28.4%zircon By volume: 81.1%quartz; 18.9% zircon Detailed solutions available. Address your requests to Rod O'Connor, Department of Chemistry, Texas A&M University, College Station, TX 77843.
Volume 58
Number 5
May 1981
435
