Use Of Ammonium Compounds Research Articles

Ammonium alum in alum-treated wooden artefacts: discovery, origins and consequences

Alum-treatment was extensively applied to archaeological wood from the Oseberg collection in the early 1900s, and was a common conservation method at the time involving impregnating objects with hot concentrated solutions of potassium alum (KAl(SO4)2⋅12H2O). This now obsolete consolidation method has led to dramatic long-term consequences, heavily affecting the state of preservation of the historical wooden artefacts, and dedicated chemical characterisation campaigns have been undertaken to better understand the degradation processes and aid development of re-treatment strategies. Analyses with Fourier transform infrared spectroscopy (FTIR), elemental microanalysis, and ion chromatography (IC) was performed, suggesting the presence of ammonium alum (NH4Al(SO4)2·12H2O) in many alum-treated wood samples, though no record exists of use of ammonium compounds during treatment of the artefacts. C/N rations of 1.70–68.8 in wood samples, and ammonium alum contents between 8 and 84% of the alum component and 23–168 mmol/100 g of total sample suggested that objects were actually treated with various mixes of potassium and ammonium alum. The two alums have similar properties, and in model studies of their behaviour under the conditions of alum-treatment appeared to form similarly acidic solutions, thus the different alum mixtures probably did not significantly influence object treatment. Nor have we observed other indications of unusual degradation pathways related specifically to the presence of ammonium alum. Nonetheless, investigations into potential re-treatment of the archaeological objects must be adjusted accordingly.

Effect of Addition of Ammonium Compounds on the Dissolution Rate of a South African Magnesium-Based Material

High dissolution rates provide better alkalinity that is important for sulphur dioxide (SO2) absorption. Therefore the rate at which magnesite dissolves is very important in wet flue gas desulphurisation process (FGD). In this study, we investigated the use of ammonium compounds for enhancing the dissolution rate of magnesium-based compounds. The dissolution rates were determined by using the shrinking core model (SCM) with surface control, i.e, [1 − (1 − X)1/3] = krt. The dissolution characteristics were investigated under the following conditions by using the pH-Stat method: temperature, 60°C; pH, 5; stirrer speed, 200 rpm; particle size 45 μm. The addition of ammonium compounds helps improve the dissolution rate of magnesium-based compounds. Upon the addition of 0.5 g of ammonium nitrate, the dissolution rate constants increased by 122%. The dissolution reaction conformed to the SCM, and chemical reaction control was the rate-controlling step.

Relation of Nitrogen Supply to the Molybdenum Requirement of Cauliflower Grown in Sand Culture

THE possible need for molybdenum by higher plants supplied with nitrogen in a form other than nitrate was first indicated by Arnon1, who obtained improved growth of barley plants in the presence of a solution containing chromium, molybdenum and nickel with an ammonium nitrogen supply. Vanselow and Datta2 and Hewitt3 later showed the need of molybdenum by plants with adequate ammonium and nitrate nitrogen. Hewitt, however, has stated3 that the absolute need for molybdenum for normal development when higher plants are supplied with ammonium nitrogen only still remains to be shown, and that the experimental difficulties of the use of ammonium compounds alone limit progress. Incorporation of solid calcium carbonate into ammonium nitrogen cultures, however, has been shown greatly to reduce the injury due to ammonium4,5. This device has been successfully applied to molybdenum-deficiency cultures using a purified source of calcium carbonate.