000			01897 am a22001813u 4500
042			_adc
100	1	0	_aNewman, Edwin S. _eauthor _9404
245	0	0	_aZinc Oxide as a Standard Substance in the Solution Calorimetry of Portland Cement
260			_bNational Institute of Standards and Technology, _c1962.
500			_a/pmc/articles/PMC6696539/
520			_aZinc oxide is the standard substance specified for calibrating the heat-of-solution calorimeters used in determining the heat of hydration of portland cement in several American and foreign cement specifications. The heats of solution of zinc oxide samples from different sources and after different heat treatments have been determined in the standard mixture of nitric and hydrofluoric acids. It is concluded that the value given in the specifications is low, that heat treatment in the range 310 to 950 °C is not critical, that small variations in the ZnO/acid weight ratio are without significance, and that analytical-reagent zinc oxide from various sources may safely be used. The mean value obtained for the heats of solution of zinc oxide from twelve sources determined in triplicate in 1.00HNO(3),0.284HF,26.38H(2)O at a ZnO/acid weight ratio of 7/425 at 25 °C was 257.82 cal/g with a standard error of 0.015 cal/g. The thermochemical calorie of 4.1840 joules is used. The temperature coefficient based on least-square fitting to 16 data points obtained in an earlier study was −0.087 cal/g-deg, with a computed standard error of 0.013 cal/g-deg. The corresponding values for heat of solution and temperature coefficient given in the specifications are 256.6 cal/g and −0.1 cal/g-deg, respectively.
540			_a
546			_aen
690			_aPhysics and Chemistry
655	7		_aText _2local
786	0		_nJ Res Natl Bur Stand A Phys Chem
856	4	1	_uhttp://dx.doi.org/10.6028/jres.066A.039 _zConnect to this object online.
999			_c620 _d620