Gravimetric weighing forms and factors

Weighing forms, molar masses and gravimetric factors F = aM(analyte)/bM(weighing form) for common gravimetric methods, all computed from the formulas.


$\ce{SO4^2-}$	$\ce{BaSO4}$	233.39	0.4116	hot dilute BaCl₂, slightly acidic	digest, filter, ignite at 800 °C to constant mass
$\ce{Ni}$	$\ce{Ni(C4H7N2O2)2}$	288.92	0.2031	dimethylglyoxime in ethanol, ammonia buffer (pH 5–9)	sintered-glass crucible, dry at 110–120 °C to constant mass
$\ce{Cl}$	$\ce{AgCl}$	143.32	0.2473	AgNO₃ in dilute HNO₃	digest in the dark, wash with dilute HNO₃, dry at 110 °C
$\ce{Ca}$	$\ce{CaO}$	56.08	0.7147	ammonium oxalate, homogeneous precipitation (urea raises the pH)	CaC₂O₄·H₂O ignited to CaO and weighed
$\ce{Fe}$	$\ce{Fe2O3}$	159.69	0.6994	ammonia precipitates hydrous iron oxide	ignited to Fe₂O₃

The coefficients a and b in F balance the key atom between analyte and weighing form, as in 2Fe/Fe₂O₃.

Sources

D. C. Harris, Quantitative Chemical Analysis, 9th ed. (2016), ch. 27.
D. A. Skoog, D. M. West, F. J. Holler, S. R. Crouch, Fundamentals of Analytical Chemistry, 9th ed. (2014), ch. 12.

Used in these lessons

Gravimetric analysis