The polymorphic forms of lactose in alcoholic suspensions have been determined by 13C CP-MAS NMR spectroscopy, employing hand-made glass inserts. Suspensions of alpha lactose monohydrate (Lα·H2O) with particle size between 2 and 200 μm were prepared by 24 h reflux or by storage for 28 d in anhydrous ethanol without agitation. These suspensions were compared to an ethanolic sub-micron lactose suspension provided by a 3 M Health Care (Loughborough). The 13C CP-MAS NMR spectra indicated that Lα·H2O dehydrated to stable anhydrous alpha lactose polymorph (LαS) whilst suspended in ethanol. In addition, strong ethanol 13C resonances were observed for some samples, indicating a liquid–solid interaction between the ethanol and lactose surface. Replacement of ethanol with anhydrous methanol, n-butanol and 3-methylbutan-2-ol implied that the solvent mediated dehydration of Lα·H2O to LαS occurs as a result of sterically controlled interactions.

Synthetic sodium aluminosilicate Bayer refinery scale has been prepared in 8 and 4.2 M sodium hydroxide solutions at four temperatures in the temperature range 80–240°C. The effect of different anions (CO32−, OH− SO42−, Cl− and C2O42−) and varying anion concentrations (10−2–10−1 M) on the type of aluminosilicate phase formed has also been investigated. These synthetic phases have been compared with industrial scale formed in different parts of low and high temperature Bayer processing plants. Synthetic and plant scales were both characterised using powder X-ray diffraction, IR spectroscopy and SEM. The plant scale crystallises as two different zeolitic aluminosilicate phases, depending on the temperature in the area of the plant. This behaviour has been shown to closely mirror the formation of synthetic scale in sodium hydroxide solutions containing the carbonate anion. The large concentration of organic ions present in Bayer liquor appear to have little effect on the type of scale formed and are relatively insignificant in promoting scale formation.

Crystallization of lactose from 10% (w/v) aqueous solutions was investigated with the use of polar antisolvents. Crystal growth was observed at 50–65% antisolvent content and showed a morphological transition from a polyhedral to needle-like habit with increasing antisolvent content, which coincided with a polymorphic transition from alpha lactose monohydrate (Lα·H2O) to beta lactose (Lβ). Where dehydrating antisolvents were employed such as methanol and ethanol, evidence of Lα·H2O dehydration to form LαS was also observed at 95% antisolvent content. Powder X-ray diffraction (PXRD) analysis of the crystals highlighted the preferred orientation effects exhibited by large crystals of this kind, indicating the difficulties experienced by the non-specialist when performing phase identification of lactose polymorphs. The same studies were applied to raffinose pentahydrate, trehalose dihydrate and mannitol to assess the effects of crystallization conditions on other pharmaceutical excipients.

•A lengthy induction period hinders the reaction of Si and water to form hydrogen.•A simple pelleting process can be used to eliminate the induction period.•The Arrhenius activation energy of the reaction was found to be 73 kJ/mol.•Hydrogen generation could be enhanced by addition of NaCl and sodium polyacrylate.One of the barriers to the use of the silicon-water reaction to generate hydrogen for hydrogen fuel cells in portable devices is the lengthy induction period of the reaction caused by the presence of the native oxide layer on the surface of the silicon. Herein is presented a simple pelleting process which can be used to effectively eliminate the induction period in the reaction of pressed silicon powders with 2 wt% sodium hydroxide solution by means of disrupting the native oxide layer. The activation energy of the reaction was found to be 73 kJ/mol by means of an Arrhenius plot. It was also found that the rate of reaction of hydrogen generation could be enhanced by mixing sodium chloride and sodium polyacrylate with the silicon powder before pressing.Figure optionsDownload full-size imageDownload high-quality image (145 K)Download as PowerPoint slide