不同形貌氢氧化镁的化学合成及影响因素

对不同形貌氢氧化镁的化学合成及外部生长环境进行了综述。尤其对影响氢氧化镁结晶性能和形貌起关键作用的因素，如碱性沉淀剂的选择、合成温度的确定、不同镁盐的影响、碱和镁盐的初始浓度及配比、水热处理、反应物的混合方式、晶形控制剂的加入等，进行了详细的阐述。     

The effect of increasing application rate of granular calcium ammonium nitrate on net nitrification in a laboratory study of grassland soils

Soil incubation studies were undertaken in controlled environment cabinets at 15°C to investigate the effect of increasing application rates of calcium ammonium nitrate (CAN) on net nitrification in two grassland soils. Granular CAN was applied to the surface of freshly collected, moist soil, at a rate equivalent to 0, 100, 200, 400, 800 and 1600µg NH ₄ ⁺ -N and NO ₃ ^- -N per gram of oven dry soil. In half the treatments finely ground CaCO₃ was incorporated into the moist soil to raise the starting pH. Changes in soil mineral N and pH were measured at weekly intervals up to six-weeks. The most probable number (MPN) technique was used to enumerate the NH ₄ ⁺ -N and NO ₂ ^- -N oxidizers at the beginning and end of the incubation.At low rates of CAN application there was considerable NH ₄ ⁺ -N oxidation to NO ₃ ^- -N during the incubation of both soils. Lime stimulated this N transformation. At high application rates (i.e. 800 and 1600 ppm) there was little change in NH ₄ ⁺ -N or NO ₃ ^- -N on either soil during the 6 week incubation, in the presence or absence of lime. The rate of NO ₃ ^- -N produced peaked at 5.6 and 3.8 mg NO ₃ ^- -N kg^–1 d^–1 on soil 1 and 2 respectively, in the presence of lime. Above a level of 400 ppm CAN (equivalent to 38 kg N ha^–1) the rate of NO ₃ ^- -N produced decreased. The higher rate of net nitrification in soil 1 compared with soil 2 was probably due to a higher number of nitrifying bacteria. Although high rates of CAN decreased the nitrifying activity of both soils there was little difference between treatments in the actual numbers of NH ₄ ⁺ -N and NO ₂ ^- -N oxidizers determined by the MPN technique.The results showed that the rate of granular CAN applied to the soil surface can influence the local activity of nitrifying bacteria and subsequent N transformations. At application rates of CAN generally used agriculturally for grass production, it is likely that net nitrification of the NH ₄ ⁺ -N in the fertilizer granule will be inhibited.     

Guayule seedling response to nitrogen fertilizers

Slow growth and high seedling mortality limit direct seeding establishment of guayule (Parthenium argentatum G.). This study was conducted to assess seedling growth enhancement by the addition of different rates and forms of N fertilizers and Ca salts. Experiments were conducted in a greenhouse with cultivar 593 under both surface and subirrigated conditions using water low in salts (salinity of 0.8 dSm^–1, SAR of 5.0 and 10 mg Ca L^–1). Under surface-irrigated conditions, seedling height and fresh plant weight increased with N application to the irrigation water to 70 mg L^–1. The best seedling growth was observed when (NH₄)₂SO₄ was added in combination with CaCl₂ or CaSO₄. Progressively less growth was observed by addition of (NH₄)₂SO₄ alone, CO(NH₂)₂ plus CaSO₄, CO(NH₂)₂ alone and Ca(NO₃)₂. When seedlings were subirrigated, however, the best growth was observed with Ca(NO₃)₂. Intermediate growth was obtained with (NH₄)₂SO₄ plus CaSO₄ and lowest growth rates with (NH₄)₂SO₄ alone. These differential responses may be explained by the differences in leaching and volatile characteristics of the N forms. Growth enhancement from N and Ca additions increased with time with significant increases 45 days after seeding. Nitrogen application with Ca may be effective amendment in promoting subsequent growth of direct seeded guayule.     

硝酸钠卤水沸点变化理论计算

根椐已有的文献与数据,采用数学模型方法,研究了硝酸钠卤水沸点在不同组成、不同压力条件下的变化关系,确定了硝酸钠卤水沸点与质量分数及压力的数学方程式;根椐硝酸钠卤水压力与组成,可以计算出硝酸钠卤水的沸点值,为新疆都善县库木塔格硝酸钠矿大规模生产硝酸钠提供了重要设计依据.     

三盐基硫酸铅的生产工艺条件研究

介绍了氧化铅法中硝酸铅法生产三盐基硫酸铅两种生产工艺 ,对氧化铅法中硫酸的加入量、酸度、温度、时间等生产条件进行了研究 ,确定了最佳生产工艺条件 ,并对两种方法进行了简单对比     

Effect of cation exchange on the distribution and movement of cations in soils with variable charge. I. Effect of lime on potassium and magnesium exchange equilibria

The influence of Ca(OH)₂ on K and Mg exchange equilibria in three New Zealand soils was studied. Calcium hydroxide was mixed with each soil to raise the pH to about 6 or 7. For each Ca(OH)₂ treatment, K and Mg exchange isotherms were determined, from which the equilibrium activity ratios were derived. Exchange coefficients and solution activity ratios were calculated according to the Gapon convention.The addition of Ca(OH)₂ produced varying effects in the Gapon exchange coefficient for both K and Mg. The magnitude and direction of change in the exchange coefficient were related to the cation initially dominating the exchange sites, rate of Ca(OH)₂ addition, soil colloids contributing to the CEC and specific interactions of Ca with these soil colloids.Addition of Ca(OH)₂ reduced the equilibrium activity ratio of all soils. Changes in the bonding strength of K and Mg with increasing CEC were suggested as a possible mechanism for this decrease.     

不同品种磷肥在土壤中的退化研究

对钙镁磷肥（FMP）、过磷酸钙（SSP）和部分酸化磷肥（PAPR）在河南郑州西岗沙土和河南西华县潮土中的退化情况进行了研究。     

Lanthanum-Magnesium and Lanthanum-Manganese Donor-Acceptor-Codoped Semiconducting Barium Titanate

BaTiO₃ powder doped with La donor and codoped with Mn or Mg acceptor was sintered at 1350°C/1 h in air. For Ladoped BaTiO₃, the room-temperature resistivity decreased to a minimum at [La³⁺] ∼ 0.15 mol%. For La-Mn-codoped BaTiO₃, the minimum resistivity occurred at [La³⁺] - 2[Mn²⁺] ∼ 0.15 mol%. When the ceramic was changed to a fine-grained insulator by high donor doping ([La³⁺] >0.15 mol%), its semiconductivity was restored, and the relatively homogeneous, coarse-grained microstructure recurred by codoping with either Mg or Mn acceptor, with the transition at [La³⁺] - 2[Mg²⁺] = 0.15 mol% or [La³⁺] - 2[Mn²⁺] = 0.15 mol%. The analogy of a compensation effect between La-Mn- and La-Mg-codoped BaTiO₃ suggested that Mn acceptor added to BaTiO₃ exists as Mn²⁺ ion in the bulk grain region; its influence on the positive temperature coefficient of resistivity behavior is then discussed.     

氢氧化镁和氧化镁中酸不溶物的研究

产硝后的高镁卤水和硫氢化钡溶液进行反应，生成氢氧化镁，酸不溶物在0．3％（质量分数）左右，但将其煅烧成氧化镁后，酸不溶物高达1．2％-2．5％（质量分数），二者酸不溶物远不成比例关系。通过对样品在分析中穿滤对比、硫酸法测定酸不溶物、碘量法测定硫化物试验，确定在生产过程中，硫氢化钡被氢氧化镁吸附，经过高温煅烧，硫氢化钡被氧化成硫酸钡，成为氧化镁中的酸不溶物，这就是氧化镁和氢氧化镁中酸不溶物不成比例的主要原因。     

Anionic Clays as Potential Slow-Release Fertilizers: Nitrate Ion Exchange

Several nitrate containing anionic clays were synthesized at different temperatures and the kinetics of NO₃ ^– release were determined to test their suitability as slow-release N fertilizers. A sample (Mg:Al = 2:1) synthesized at 60°C with smaller particle size released 75, 86 and 100% of its NO₃ ^– in 1, 3 and 7 days, respectively when equilibrated with a simulated soil solution. On the other hand, the 175°C/2 hrs sample with larger particle size released 65, 77 and 84% of its nitrate in 1, 3 and 7 days, respectively. Another anionic clay (synthesized at 175°C/24 hrs) of higher charge density (Mg:Al = 2:1) containing NO₃ ^– was equilibrated with a 0.012 N NaCl or Na₂CO₃ to test the role of different anions in releasing the NO₃ ^– anion from the interlayers. The results showed that Cl^– released more NO₃ ^– than did CO₃ ^2– from this anionic clay after all the treatment times probably as a result of the CO₃ ^2– anion blocking the release of NO₃ ^– from the interior of the crystals. When a lower charge density (Mg:Al = 3:1) sample (synthesized at 175°C/48 hrs) was equilibrated with 0.02N solution of anions the release of nitrate was as follows: Cl^– < F^– < SO₄ ⁼ CO₃ ^2–. These results suggest that the divalent SO₄ ⁼ and CO₃ ^2– anions are more effective in the release of NO₃ ^– from this lower charge density anionic clay. Time-resolved structural analysis of NO₃ ^– exchange with CO₃ ^2– in the above anionic clay using synchrotron x-ray diffraction showed that ion exchange is rapid because of small crystal size and lower charge density. Thus the release of NO₃ ^– from anionic clays is an interplay among the type of anions present in soil solution, their concentration, pH of soil solution, the charge density and crystal size of anionic clay etc.