Studies on Organic Compounds containing Water or Solvent of Crystallization. X. Hydrate of Calcium 5-Ethyl-5-pentylbarbiturate.

Abstract

In order to determine the amount of crystal water in calcium 5-ethyl-5-pentylbarbiturate, examinations were made on the action of water vapor on the hydrate and the anhydrate by the use of a quartz spring balance and a mercury manometer which may be able to estimate the reaction amount and equilibrium pressure. The amount of crystal water obtained from the flat part of the desorption curves corresponds to dihydrate. The rate of dehydration was examined over the temperature range of 20°to 50°and the rate of dehydration may be expressed by the formula (1-α)1/8=1-<kt>/r, where k is the rate constant, the fraction dehydrated at time t is α, and r is the initial radius of particle. From the experimental data, it was estimated that the activation energy for dehydration reaction of the hydrate is 9.5 kcal. / mole.