Dissolution rate data obtained with sulfathiazoie-povidone(PVP) co-precipitates and hydrocortisone-povidone co-precipitates were compared to cellophane membrane diffusion data obtained with the co-precipitates. The hypothesis, that the rate-limiting drug phases in the co-precipitate dissolution experiments were high energy amorphous phases of the drug, was tested. In regions of the dissolution rate studies where the carrier effects due to the PVP-drug complexes were small, the dissolution rates for the two PVP-drug systems agreed well with the results of the membr~e diffusion experiments. The normalized fluxes were found to be about 3.5 for the high energy phase of sulfathiazole and 14-18 for that of hydrocortisone.

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A major problem in space flight has been leakage of fluids and gases and is particularly serious at launching. Comparatively small leaks of propellant and/or oxidizer can cause disasterous explosions. The emphasis on the initial studies reported in this article has been the development of an improved method for leak detection during factory test and checkout prior to launching and space flight. However, the long-range objective of a versatile leak detection system that could be used in space, during launching, as well as during static testing, was kept in view. A leak detection technique was developed based on the use of Kr65 as a radiotracer.This technique is described and is believed to be more versatile than any other. Krypton has sufficient solubility to be. used as a tracer in all liquids tested, except hydrogen. Leakage rates can be determined with greater precision in the order of 0.005 SCIM (Standard Cubic Inches per Minute) than by any other methods. Because of safety and ease of use, radiokrypton shows great promise for many applications. METHODS OF LEAK DETECTION

A major problem in space flight has been leakage of fluids and gases and is particularly serious at launching. Comparatively small leaks of propellant and/or oxidizer can cause disasterous explosions. The emphasis on the initial studies reported in this article has been the development of an improved method for leak detection during factory test and checkout prior to launching and space flight. However, the long-range objective of a versatile leak detection system that could be used in space, during launching, as well as during static testing, was kept in view. A leak detection technique was developed based on the use of Kr65 as a radiotracer.This technique is described and is believed to be more versatile than any other. Krypton has sufficient solubility to be. used as a tracer in all liquids tested, except hydrogen. Leakage rates can be determined with greater precision in the order of 0.005 SCIM (Standard Cubic Inches per Minute) than by any other methods. Because of safety and ease of use, radiokrypton shows great promise for many applications.