. 1965 Sep-Oct;69A(5):423–438. doi: 10.6028/jres.069A.045

Table 7. Comparison of the thermodynamics of vapor-equilibrium reactions of table 6 calculated by various methods.

Reference	T	Calculations from vapor-equilibrium data				Calculations from calorimetric data		Difference (method II—calorimetric data)
		Method I assuming ΔC_p=0		Method II ΔC_p from calorimetric data		Calculations from calorimetric data		Difference (method II—calorimetric data)
		$Δ H_{T}^{°}$	$Δ S_{T}^{°}$	$Δ H_{T}^{°}$	$Δ S_{T}^{°}$	$Δ H_{T}^{°}$	$Δ S_{T}^{°}$	$δ Δ H_{T}^{°}$	$δ T Δ S_{T}^{°}$	$δ Δ G_{T}^{°}$
	°K	kcal mol⁻¹	cal deg⁻¹ mol⁻¹	kcal mol⁻¹	cal deg⁻¹mol⁻¹	kcal mol⁻¹	cal deg⁻¹mol⁻¹	kcal mol⁻¹	kcal mol⁻¹	kcal mol⁻¹
Meschi and Searcy [31]	1650	345.2±27.3^a	117.5±16.4^a	345.6±27.3^a	117.8±16.4^a	351.1±2.1^b,c	130.2±0.3	−5.5	−20.5	+15.0
Prescott and Hincke [36]	1850	257.4±14.9	92.6±8.0	257.2±14.9	92.5±8.0	250.3±1.7	87.3±0.3	+6.9	+9.6	−2.7
Prescott and Hincke [37]	2150	535.6±88.0	239.8±41.5	535.0±87.8	239.6±41.4	566.8±7.2	248.9±0.7	−31.8	−20.0	−11.8
Brunner [38]	2100	467.6±3.4	209.4±1.7	466.1±3.4	208.7±1.6	567.6±7.2	249.3±0.7	−101.5	−85.3	−16.2
Grjotheim et al., [41]	1400	297.2±6.5	172.4±4.7	297.2±6.5	172.3±4.7	301.3±4.7	167.5±0.3	−4.1	+6.7	−10.8

These figures following the ± symbols are standard deviations defined for the values of ΔH° by:

S_{b} = {\frac{S_{y}^{2}}{Σ x_{i}^{2} - {(Σ_{x_{i}})}^{2} / k}}^{1 / 2}, and of Δ S^{°} by : S_{a} = {\frac{S_{y}^{2} Σ x_{i}^{2}}{k Σ x_{i}^{2} - {(Σ x)}^{2}}}^{1 / 2},

where

S_{y}^{2} = Σ δ_{i}^{2} / (k - 2), δ_{i}

the deviation of the experimental value from the “least-squared” value, k the number of observations, and x_i-=1/T_i [42].

These figures following the ± symbols were obtained from the relation $(\sum ϵ_{i}^{2}) 1 / 2,$ where ϵ_i is the estimated uncertainty of the calorimetric data used.

These values of ΔH° are based on the $Δ H_{f}^{°}$ (298 °K) for Al₄C₃ reported by King and Armstrong [26].