35.9: Recommended Primary Standards

All compounds are of the highest available purity. Metals are cleaned with dilute acid to remove any surface impurities and rinsed with distilled water. Unless otherwise indicated, compounds are dried to a constant weight at 110 ^oC. Most of these compounds are soluble in dilute acid (1:1 HCl or 1:1 HNO₃), with gentle heating if necessary; some of the compounds are water soluble.

Element	Compound	FW (g/mol)	Comments
aluminum	Al metal	26.982
antimony	Sb metal	121.760
	\(\ce{KSbOC4H4O6}\)	324.92	prepared by drying \(\ce{KSbC4H4O6 * 1/2H2O}\) at 100 °C and storing in a desicator
arsenic	As metal	74.922
	\(\ce{As2O3}\)	197.84	toxic
barium	\(\ce{BaCO3}\)	197.84	dry at 200 oC for 4 h
bismuth	Bi metal	208.98
boron	\(\ce{H3BO3}\)	61.83	do not dry
bromine	KBr	119.01
cadmium	Cd metal	112.411
	CdO	128.40
calcium	\(\ce{CaCO3}\)	100.09
cerium	Ce metal	140.116
	\(\ce{(NH4)2Ce(NO3)4}\)	548.23
cesium	\(\ce{Cs2CO3}\)	325.82
	\(\ce{Cs2SO4}\)	361.87
chlorine	NaCl	58.44
chromium	Cr metal	51.996
	\(\ce{K2Cr2O7}\)	294.19
cobalt	Co metal	58.933
copper	Cu metal	63.546
	CuO	79.54
fluorine	NaF	41.99	do not store solutions in glass containers
iodine	KI	166.00
	\(\ce{KIO3}\)	214.00
iron	Fe metal	55.845
lead	Pb metal	207.2
lithium	\(\ce{Li2CO3}\)	73.89
magnesium	Mg metal	24.305
manganese	Mn metal	54.938
mercury	Hg metal	200.59
molybdenum	Mo metal	95.94
nickel	Ni metal	58.693
phosphorous	\(\ce{KH2PO4}\)	136.09
	\(\ce{P2O5}\)	141.94
potassium	KCl	74.56
	\(\ce{K2CO3}\)	138.21
	\(\ce{K2Cr2O7}\)	294.19
	\(\ce{KHC8H4O2}\)	204.23
silicon	Si metal	28.085
	\(\ce{SiO2}\)	60.08
silver	Ag metal	107.868
	\(\ce{AgNO3}\)	169.87
sodium	NaCl	58.44
	\(\ce{Na2CO3}\)	106.00
	\(\ce{Na2C2O4}\)	134.00
strontium	\(\ce{SrCO3}\)	147.63
sulfur	elemental S	32.066
	\(\ce{K2SO4}\)	174.27
	\(\ce{Na2SO4}\)	142.04
tin	Sn metal	118.710
titanium	Ti metal	47.867
tungsten	W metal	183.84
uranium	U metal	238.029
	\(\ce{U3O8}\)	842.09
vanadium	V metal	50.942
zinc	Zn metal	81.37

Sources:

• Smith, B. W.; Parsons, M. L. J. Chem. Educ. 1973, 50, 679–681
• Moody, J. R.; Greenburg, P. R.; Pratt, K. W.; Rains, T. C. Anal. Chem. 1988, 60, 1203A–1218A.

---