Layer test, powder stability tests

Haid, Becker and Dittmar Stability Test (Designed for high explosives). 42g of powdered explosive, previously dried over phosphorous pentoxide, is introduced through a side tube into a glass vessel connected with a manometer which is in the form of a U-tube and contains mercury covered with a layer of paraffin oil. The glass vessel is also fitted with a side tap. The ensemble is heated at 75° for several hours and pressures are recorded in mm of Hg as a function of time. The steeper the pressure-time curve the less stable is the explosive... 

More rudimentary tests to identify the stability of powders are the so-called "hot plate" tests. Here, the substance is placed in a well-defined manner (circular, specified thickness of the layer, and so forth) on a hot plate with a controlled temperature. The temperature in the center of the layer is recorded continuously, and the progress of the self-heating is followed. Observations are made if self-heating of the substance occurs, the induction period of such self-heating, and the extent of the effect such as smoldering or spontaneous ignition. 

Vaginal tablets containing lactobacilli have been used in order to restore the normal vaginal flora. Formulation of these delivery systems requires specific proceedings in order to provide viability of lactobacilli and stability of the final product. Freeze drying of bacterial suspensions has been tested to obtain lyophilized powders for tablet production [81]. These powders were shown to be processable and tablet production was easy and reproducible. Also, the use of double-layer tablets (fast-release layer and slow-release layer) seems to be an interesting approach to lactobacilli administration. 

The standard conditions used to evaluate the thermal stabilities of the samples obtained, were the same as reported previously [5] (i) Stable/unstable under heating in static air at 120°C (pre-heated ovens) overnight in unsealed standard sample holders. Approximately 1 g of sample was used, giving layers of ca. 5 mm thickness, (ii) Stable/unstable under heating (heating rate 5°C/min) at 400°C in a flow of dry air (100 ml/min) overnight, the samples (ca. 1 g) were spread out in layers of ca 1 mm in quartz trays. The phases obtained were identified by their powder X-ray diffractograms, recorded before and after the tests. 

Matthews, 2000). A phosphate salt solution and an aqueous suspension of HAp powder were used as an electrolyte for PEO and EPD, respectively. The corrosion resistance was assessed by potentiodynamic polarisation tests in a buffered physiological solution (see also Kwok et al., 2009). The results of this study indicated that a hybrid combination of PEO and EPD produces an osseoconductive phase-pure ITAp layer and an anticorrosive titania interlayer that promise to provide good mechanical and biochemical stability in the highly corrosive environment of the human body. Other studies involving titania bond coats include Albayrak and Altintas, 2010 Paluszkiewicz, Dlugon andKwiatek, 2012 Rath etal., 2012 and Jain etal. (2013). 

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