Use of ferrous hydroxide for determination of nitrate in soil extracts

Abstract

A simple steam distillation method of determining nitrate is described that is not subject to interference by substantial amounts of phosphate or silicate. It involves use of FeSO₄ and MgO for reduction of nitrate to ammonia. The method is rapid and precise, and tests reported show that it is satisfactory for nitrate analysis of soil extracts.     

适宜热烫条件保持双孢蘑菇片品质和颜色

为保持双孢蘑菇片的品质和颜色,采用85、90、95和100℃的热水分别对双孢蘑菇片进行不同时间的热烫处理,以未经热烫的双孢蘑菇片为对照,测定其干片抗坏血酸和总酚含量、抗氧化活性及其颜色的变化。结果表明:热烫后双孢蘑菇片的抗坏血酸和总酚含量分别损失66.67%~93.33%和12.33%~59.49%,抗氧化活性减弱16.86%~42.75%;与未热烫样品相比,热烫可使双孢蘑菇片亮度L值下降11.23%~30.63%,而色度变化不大,但总色差从10.12±0.55增到22.86±0.21。综合考虑热烫温度和时间对双孢蘑菇片抗坏血酸、总酚、抗氧化活性和颜色的影响,确定双孢蘑菇片的较佳热烫条件为85~95℃温度下处理1~2 min,在此条件下能较好的保持双孢蘑菇片的营养品质和颜色。     

用响应面法优化小球藻絮凝沉降工艺的研究

以氢氧化钙为絮凝剂,对海水小球藻Chlorella vulgaris絮凝工艺效果进行了试验研究.单因素试验结果表明,当絮凝时间为60～ 80 min、氢氧化钙添加量为0.6～0.8 g/L和藻液pH为8～10时,最有利于小球藻的采收.在单因素试验的基础上,利用响应面法对小球藻的絮凝条件进行了优化,建立了二次回归模型.通过分析得出：各因素对小球藻采收率均有极显著性影响（P＜0.01）,影响次序为氢氧化钙添加量＞絮凝时间＞藻液pH;絮凝时间与藻液pH以及氢氧化钙添加量与藻液pH的交互作用对小球藻采收率均有极显著性影响（P＜0.01）.利用回归方程预测小球藻的最佳絮凝条件,当絮凝时间为77 min、氢氧化钙添加量为0.7 g/L、小球藻液pH为9.3时,小球藻的采收率可达93.9％.     

鸡新城疫和产蛋下降综合征二联灭活氢氧化铝胶疫苗免疫研究

使用鸡新城疫病毒LaSota株和产蛋下降综合征病毒分离株HE03株制备鸡新城疫和产蛋下降综合征二联灭活氢氧化铝胶疫苗。把40只16周龄SPF蛋鸡分成A、B 组,分别是30只、10只。A组接种0.5 mL鸡新城疫和产蛋下降综合征二联灭活氢氧化铝胶疫苗,B组作为对照组,每隔14 d采集血清样本直到接种后第6周。至22周龄时,A组再次分成A1和A2两组。A2组与B组的鸡接受强致病性的产蛋下降综合征病毒攻击。结果表明,A组在不同时间采集的血清抗鸡产蛋下降综合征病毒的最高的抗体出现在接种后的第4周,抗鸡产蛋下降综合征病毒的HI抗体滴度从1∶128到1∶512不等,几何平均滴度（GMT）为1∶111;第4周时,抗鸡新城疫病毒的HI抗体滴度GMT为1∶134。该疫苗能保护鸡抵抗强致病性的产蛋下降综合征病毒和鸡新城疫病毒的感染,B组在攻毒感染后产蛋率显著下降,出现畸形蛋、软壳蛋和无壳蛋。     

喷涂型农用薄膜防水滴剂的制备

 报道一种喷涂型农用薄膜防水滴剂的制取和使用方法.讨论了氢氧化铝和硅酸混合溶胶的稳定性问题.     

氢氧化钙尿素复合处理芨芨草的效果研究

分别用4％尿素、4％尿素 4％氢氧化钙处理芨芨草，试验结果表明：氢氧化钙尿素复合处理剂可极显著(P＜O．01)提高芨芨草粗蛋白含量，比对照组提高142．61％，增加5．79个百分点。NDF舍量比对照组降低11．51％(P＜0．01)。钙含量比对照组提高1．92倍(P＜0．01)。4％尿素处理芨芨草后．芨芨草DM中CP含量比对照组增加145．81％(P＜0．01)。氢氧化钙尿素复合处理芨芨草后．可分别提高芨芨草DM、OM、NDF有效降解率55．08％、62．04％、28．89oA(P＜0．01)。4％尿素可分别提高芨芨草DM、0M、NDF有效降解率46．61％、50．87％、18．80％(P＜0．01)。     

秸秆饲料尿素处理效应的研究

本试验系统地研究了不同处理方法对秸秆饲料干物质、中性洗涤纤维、酸性洗涤纤维、酸性洗涤木质素、半纤维素、纤维素及木质素消失率的影响.结果表明,碱和尿素,可以明显作用于秸秆的各组分,5%氢氧化钠23℃处理7天、5%尿素27℃处理28天,能显著提高纤维素、半纤维素及木质素在瘤胃中的消失率,是提高秸秆营养价值的有效方法.     

Bacterial Populations of Broiler Carcasses Washed in Mixtures of Potassium Hydroxide and Lauric Acid

The bactericidal effect of mixtures of KOH and lauric acid (LA) on the microflora of broiler carcasses was examined. Carcasses were washed by shaking in KOH-LA for 1 min on a mechanical shaker. In one set of experiments, the population of bacteria recovered from carcasses following each of 3 successive washes in 1.0% KOH-2.0% LA or in distilled water (control) was enumerated. The number of total plate count bacteria, Campylobacter, and Escherichia coli in aliquots of whole-carcass-rinses of the washed carcasses was determined. Results indicated that fewer bacteria were generally recovered from carcasses after each successive wash in KOH-LA or distilled water, but significantly fewer bacteria were recovered from carcasses washed in KOH-LA than from carcasses washed in distilled water. Bacteria recovered from carcasses after the first and third wash in KOH-LA were identified using the MIDI Sherlock Microbial Identification System. Gram-positive and gram-negative bacteria were identified in the bacterial flora of carcasses washed once in KOH-LA; however, only gram-positive cocci were identified in the bacterial flora of carcasses washed 3 times in KOH-LA. Additional experiments were performed to compare the number of bacteria recovered from carcasses washed 2 times in 0.25% KOH-0.5% LA, 0.5% KOH-1.0% LA, or 1.0% KOH-2.0% LA or in distilled water (control). Results indicated that significantly fewer bacteria were recovered from carcasses washed in higher concentrations of KOH-LA than from carcasses washed in lower concentrations of KOH-LA. Findings from these experiments show that washing carcasses in KOH-LA can reduce carcass contamination by bacteria responsible for human foodborne diseases and spoilage of fresh poultry.     

氢氧化钠熔融-氟离子选择电极法测定土壤全氟含量的熔融条件研究

采用氢氧化钠为土壤全氟测定熔融试剂,设置了氢氧化钠状态、试样与熔剂比例、称样量、熔融温度、熔融时间等熔融条件的单因子试验,按选择的熔融条件,采用氟离子选择电极法,利用GBW07418、GBW07420标准样品进行方法检验。试验表明,采用氢氧化钠熔融—氟离子选择电极法测定土壤全氟含量时,熔融剂氢氧化钠形态、试样与熔融剂比例、称样量、熔融温度、熔融时间对土壤全氟测定值均会产生影响。采用氢氧化钠溶液作为熔融剂、称样量0.5000g、试样与熔融剂比例1：8、熔融温度600℃、熔融时间30min的熔融条件,检测方法的精密度、准确度可达到检验要求。     

Stability behavior of soil colloidal suspensions in relation to sequential reduction of soils

The cause of the decrease in the Fe²⁺ concentration of the soil solution in the later period of soil waterlogging was investigated. After 7-d incubation of the soil solutions separated from previously waterlogged soils (PWdS), a greyish precipitate (PPT) was observed in the soil solutions. The color of the PPT became reddish brown after separation from the solutions and freeze-drying. The PPT observed in 14-d-PWdS contained 352.6 g Fe kg^-1, 62.5 g C kg^-1, 22.6 g P kg^-1, 11.3 g Si kg^-1, 9.9 g N kg^-1, 0.7 g Al kg^-1 and a trace amount of Mn. However, Ca, Mg, K, and Na could not be detected. It was concluded that the separated PPT was dominated by amorphous ferric hydroxide based on the chemical analysis, broad IR absorption band at 585 cm^-1 and exothermic peak at 301°C. The data of chemical analysis and the characteristic IR bands of the PPT suggested that organic substances and presumably aluminosilicate anion were adsorbed onto the freshly-formed ferric hydroxide. The dominant phase of the greyish PPT in the reductive soil solution was considered to be ferrous PPT and was assumed to consist mainly of carbonate and/or hydroxide, and concomitantly of phosphate. The formation of the ferrous PPT in the soil solution in the later period of soil waterlogging was considered to (i) cause the decrease of concentration of Fe²⁺ ion and of other divalent cations such as Ca²⁺ due to the re-adsorption of Ca²⁺ on soil clays through the cation exchange reaction with Fe²⁺ ion, and consequently (ii) enhance the dispersion of the soil colloidal suspension.