NIST and standards for calorimetry

Enthalpies of solution of C-alkylresorcin[4]arenes in alcohols at T= 298.15 K

“…The calorimeter was immersed in a thermostat developed in our laboratory and the temperature was controlled with a Julabo LC6 unit; the control was better than T = 298.15 ± 0.005 K. The calorimeter was tested by measuring enthalpies of solution of KCl in water and NaCl in water at T = 298.15 K, the values obtained were 17.22 ± 0.09 kJ Á mol À1 and 4.29 ± 0.01 kJ Á mol À1 , respectively. These values are in good agreement with those reported in literature, which are 17.58 ± 0.01 kJ Á mol À1 [20] and 4.21 ± 0.01 kJ Á mol À1 [21], respectively.…”

Analytical techniques for quantification of amorphous/crystalline phases in pharmaceutical solids

“…In practice, the crystallinity is determined by a linear relationship between heats of solution and crystalline content of physical mixtures of crystalline and amorphous standards in different ratios. It can also be directly calculated by using the following equation:93 where, $\Delta H_{\rm s}^o$ , $\Delta H_{\rm c}^o$ and $\Delta H_{\rm a}^o$ are the heats of solution to infinite dilution (in any fixed solvent) of the sample, the 100% crystalline standard, and the 100% amorphous standard, respectively.…”

“…SC was found to facilitate the comparison of crystallinity of the β‐lactam antibiotics with their chemical stability 93. It could also detect and quantify the amorphous contents of unmicronized and micronized drug100 as well as examine the effect of different grinding times101 or different methods of preparation of amorphous forms,63 when XRD and DSC failed to do so.…”

Enthalpies of dissolution of long chain-length alkyltrimethylammonium bromide salts in water at temperatures from 278.15 to 308.15 K

“…The calorimeter vessel was immersed in a thermostat developed in our laboratory whose temperature was controlled with a Julabo LC6 unit to better than ±0.005 K at all temperatures studied. The calorimeter was tested by measuring the dissolution enthalpies in water of potassium chloride (KCl(s)) at T = 298.15 K and sodium chloride (NaCl(s)) at 308.15 K, according to literature recommendations [21,22]. The values obtained, (17.46 ± 0.21) kJ⋅mol -1 and (3.09 ± 0.04) kJ· mol -1 , respectively, were in excellent agreement with the corresponding literature values of (17.584 ± 0.017) kJ⋅mol -1 [21] and (3.068 ± 0.008) kJ⋅mol -1 [22].…”