Evolved gas detection techniques: II. Volume—Temperature

A simple constant pressure-variable volume evolved gas detection apparatus is described. It consists of a glass system in which the pressure change activates a motor-driven variable-volume gas syringe. A slidewire and contact on the syringe plunger permits the recording of the change in volume of the system. Use of the apparatus is illustrated by the thermal dissociation reactions of KHCO₃, HgO, CaC₂O₄·H₂O, BaO₂, and Cd, Cu, Co, Ni and Mg carbonates.     

Advances in Photochemistry: Volume 6

Advances in Photochemistry: Volume 6 , W. A. NOYES, Jr., G. S. HAMMOND and J. N. Pins, Jr. (Editors).     

Volume properties of a ternary system: Water-urea-amino acid. Dilute and concentrated solutions

Partial molar volumes $ \bar V_U^0 $ \bar V_U^0 of amino acids in an aqueous urea solution are studied. For a saturated urea solution $ \bar V_U^0 $ \bar V_U^0 equals the molar volume of the amino acid, therefore, in the saturated solution, the amino acid dissolves without changing the system volume. Hydrophobic effects are manifested in the volumetric characteristics only in dilute (<1 mol/kg) urea solutions. Within a three-layer hydration model, the numbers of amino acid hydration are found. By the example of alanine and leucine, it is shown that their decrease with increasing urea concentration is determined by a zwitterionic moiety and does not depend on the size of the hydrocarbon radical of the amino acid.