Microstructure of acrylamide-acrylic acid copolymers: 1. As obtained by alkaline hydrolysis

Kinetics of alkaline hydrolysis of high molecular weight commercial polyacrylamide were studied by two different methods proposed by Fuoss and Higuchi. Compositional triad distributions and cotacticity parameters are determined from results obtained by ¹³C (¹H) nuclear magnetic resonance of carbonyl and methine resonance patterns of partially hydrolysed polyacrylamides. It is established that acrylate monomers tend to occur as isolated groups along the molecular chain but it is not possible to assert whether there is racemization or not during the reaction.     

Direct potentiometric titration of oxirane oxygen by hydrogen chloride-acetic acid

Summary A new direct potentiometric titration method for the determination of oxirane oxygen has been developed. This method is applicable to a great variety of epoxy compounds and epoxy plasticizers. Carboxyl groups do not interfere, and a greater accuracy and reproducibility are obtained than in any of the indirect methods used. Paper presented at the 29th Fall Meeting of the American Oil Chemists’ Society, Philadelphia, Pa., Oct. 10, 1955.     

磷酸电位滴定法的改进及其应用

对传统的磷酸电位滴定方法进行了系统研究,比较了两种沉淀剂(CaCl2和AgNO3)的滴定结果.提出的改进方法为:用CaCl2作沉淀剂,控制第二滴定突跃的PH在10.3以内,并将pH 7作为第三滴定终点.测定结果表明:改进的磷酸电位滴定方法,小仪结果更准确,而儿测定时间缩短一半.对3种磷酸酯/盐的含量分析测试结果表明,该改进的方法对提高相关目标产物含量、改进合成方法及精确调控产品性能更具指导意义.     

电位滴定法连续测定样品中盐酸和醋酸含量

建立了连续测定盐酸和醋酸含量的分析方法,对电位滴定、酸碱滴定及沉淀滴定3种方法进行了比较。结果表明,连续电位滴定方法操作简单、准确可靠、滴定终点突跃明显、重现性好。     

Effect of including a hydrophobic comonomer on the rheology of an acrylamide-acrylic acid based copolymer

Synthesis and design of polymer systems based on acrylamide for enhanced oil recovery (EOR) is essential for reservoirs with high salinity and high temperature conditions. The use of associative monomers or the modification of the polymers with hydrophobic functional groups represents a promising alternative that extends the use of chemical EOR. In this study, terpolymers based on acrylamide, acrylic acid and butyl methacrylate were synthesized and the rheological properties of aqueous solutions of the obtained polymers at different pH values, and salt concentrations were evaluated. The results show that at alkaline conditions the viscosity of aqueous solutions of a polymer synthesized with 68.6 wt% of acrylamide, 22.9 wt% of acrylic acid and 8.6 wt% of butyl methacrylate increases by a factor of more than 1,000 at a 3 wt% concentration. Also, all polymers with the hydrophobic modification showed higher viscosity in saline solutions compared to their acrylamide-acrylic acid analogue.     

The potentiometric behaviour of copolymers of methacrylic acid in water-ethanol solutions

Summary The synthesis is reported of copolymers of styrene with methacrylic acid and of methyl methacrylate with methacrylic acid by radical copolymerization, of copolymers of methyl methacrylate with methacrylic acid by partial alkaline hydrolysis of poly(methyl methacrylate), and of block copolymers of styrene with methacrylic acid. Modified titration curves of all these copolymers were recorded in water and water-ethanol solutions. In a solution containing 50 mass.% ethanol, only small differences could be observed between the potentiometric behaviour of the individual copolymers and polymethacrylic acid. Also, there were no essential differences in any of the solvents used between the potentiometric behaviour of block copolymers of styrene with methacrylic acid, on the one hand, and polymethacrylic acid, on the other. On the contrary, maxima and minima were always observed on the modified titration curves of statistical copolymers with a higher content of the hydrophobic comonomer in solutions with a high water content. Thus, using the modified titration curves, it is possible to decide whether a given copolymer is of the block or statistical type.     

电位滴定法在标定标准滴定溶液中的应用

探讨用自动电位滴定仪标定标准滴定溶液,并与国家标准中以指示剂判定滴定终点的方法进行了比对。结果表明,自动电位滴定法标定EDTA、硝酸银标准滴定溶液,滴定结果准确度高,数据重现性高于标准法,可满足化验室分析工作的需要。     

电位滴定法在聚酰亚胺合成中的应用

未完全环化的酰胺酸对聚酰亚胺的性能有重要影响,用电位滴定法可直接测定其含量。对常规的电位滴定装置进行了改进,用VB语言编写了上位机操作软件,实现了滴定控制、数据采集和处理等功能,建立了一套自动电位滴定测试系统,可用于测定二步法合成聚酰亚胺过程中剩余聚酰胺酸的含量。测定结果表明:数据的重现性好、灵敏度高,且操作方便,为进一步开展聚酰亚胺合成及其亚胺化动力学研究提供了可行的途径。     

HCl-H_2S-H_2O体系缓蚀剂的合成及应用性能

以对苯二胺、甲醛、膦酸丁酯合成含氮有机膦缓蚀剂,研究该缓蚀剂对A3钢片缓蚀效果。结果表明,最佳反应条件为:n(胺)∶n(醛)∶n(酯)=1∶4∶2,反应温度50℃,反应时间3 h。该缓蚀剂加量≥30 mg/L时,在pH 6～8的HCl-H_2S-H_2O体系加热回流状态下,腐蚀速率低于0.715 g/(m²·h),降低了HCl-H_2S-H_2O盐水体系对钢铁腐蚀,SEM分析表明,缓蚀剂分子在钢铁表面形成致密保护膜。     

Automatic potentiometric titration of surface acidity of carbon black

Acid strength distribution on commercial carbon blacks and chemically oxidized carbon blacks was measured by automatic titration using sodium hydroxide solutions as titrants. The titration curves show that the weaker acids with pKa between 7.0 and 11.0 occur in the amount of 0.025–0.490 m eq/g, the stronger ones with pKa between 2.0 and 7.0 in the amount of 0–0.475 m eq/g and trace amount of pKa range below 2.0. The acid strength distribution obtained by this method coincides with that by the Boehm method. The observed amounts of total acid exceed active hydrogen contents obtained by the Zerewitinoff method in the carbon blacks. Three different oxidizing agents were used to determine their effect on carbon black acidity. Nitric acid produced acidic groups at the highest surface density; H₂O₂ produced a predominance of weaker acids; hot air produced stronger acids with an increase of specific surface area.     

电位滴定法测定铜镍锰钎料中的锰含量

本文建立了高锰酸钾电位滴定法测定铜镍锰钎料中锰的方法,研究了测定锰的条件。结果表明：在焦磷酸钠介质中,采用Pt指示电极和Ag参比电极指示滴定终点,用高锰酸钾溶液滴定Mn（Ⅱ）为Mn（Ⅲ）,测定约30%锰含量,相对误差小于±0.14%,标准加入回收率在99.60%～100.50%之间。方法准确度高,重现性和选择性好,操作简便,重点敏锐,结果令人满意。     

自动电位滴定法定量测定烷基羧基甜菜碱类表面活性剂含量

研究了酸化剂种类、酸化温度及时间等对电位滴定法测定烷基羧基甜菜碱含量的影响。结果表明,酸化剂的pH,酸化温度和时间等对测定结果有显著影响,关键是保证甜菜碱分子的完全酸化。以pH=3的醋酸-醋酸钠缓冲溶液作酸化体系,于70～80℃下酸化2～3 h后用十二烷基硫酸钠(SDS)进行电位滴定,对C12-C18单长链烷基甜菜碱以及双十二烷基甜菜碱都能得到满意的结果,回收率达到97%～102%。以硫酸作酸化剂,将pH提高到2左右,于室温下酸化1 h后滴定,亦可得到满意的结果。对工业级甜菜碱样品,其中的游离叔胺在测定条件下也定量参与滴定反应,所得结果为甜菜碱和相应叔胺的总量,由于叔胺含量能用独立的方法测出,借助于电位滴定可以测出甜菜碱含量。     

电位滴定法测定苯乙烯中的总醛含量

根据GB/T 12688.5—2019标准,使用T-50全自动电位滴定仪测定苯乙烯中总醛含量,探讨了实验操作条件对测定结果的影响。结果表明:在确保分析的标准溶液及有关试剂的准确有效的前提下,滴定过程中滴定杯中的溶液搅拌速率为30%,搅拌时间为30 min,滴定终点电位为295 mV时,采用电位滴定法测定苯乙烯中总醛含量,其加标回收率为97.14%～103.33%,相对标准偏差为0.000～0.477%;该分析方法具有分析速度快、灵敏度高、操作简便等优点。     

Differentiation and quantification of surface acidities on MWCNTs by indirect potentiometric titration

Wet-chemically oxidized carbon nanotubes (CNTs) generally exhibit both covalently-bound acidic functional groups on the surface and surface-adsorbed acidic substances, i.e. carbonaceous CNT fragments from the oxidation procedure. Direct potentiometric titration of oxidizable high surface area materials with dynamically desorbing acidic fragments is slow and inaccurate. Adsorbed acidic fragments are deprotonated by sodium hydroxide and form anions in solution which is not the case for covalently bound acidic groups on the CNTs, so the following filtration after NaOH treatment separates desorbable acidic substances from non-desorbable or covalently bound groups. For a known concentration of NaOH, titration of the eluate with hydrochloric acid (HCl) allows determination of the concentrations of both types of acidities. However, contrary to reports in the literature, the NaOH consumed by non-desorbed acidic groups has to be accounted for and impedes distinction of desorbed acidic groups via their pK_a values. Results are presented of a study on the information content and the reliability of indirect potentiometric Boehm titration for different oxidized multi-walled CNTs.     

SBR中皂含量测定电位滴定终点的研究

试验研究了用盐酸标准溶液滴定SBR中皂含量时电位滴定终点pH值对测定结果的影响,结果表明,按现行方法中规定的滴定终点进行试验,皂含量测定结果包括了胶料中防老剂及填充油中的其它碱性物质,试验确定了pH值4.8为新的滴定终点,使测定值与真实值更为接近。平行测定相对标准偏差为1.54%（n=8）。     

Assay of quaternary ammonium antimicrobial compounds by aqueous potentiometric titration

An automatic potentiometric titration method for the determination of quaternary ammonium antimicrobial compounds at the macro level is described. The procedure involves the use of standard sodium lauryl sulfate as the titrant and a nitrate ion-selective or surfactant electrode to detect the end point. The method, which includes a new, simpler means of titrant standardization, avoids the use of hazardous solvents such as chloroform, which are employed in two-phase titration methods currently in common use. In this study, four frequently produced antimicrobial quats were titrated potentiometrically and by a two-phase titration using bromphenol blue as the indicator. Comparison of results shows the automatic potentiometric method to be accurate, more precise, easier, faster, and generally better suited for use in a production laboratory than the two-phase approach. The nitrate and the surfactant electrodes appear to be equal in performance.     

Estimation of α and β peptide bonds in thermal poly(aspartic acid) by potentiometric titration

Summary A potentiometric titration method for the estimation of the configuration ( and peptide bonds, I and II) of poly (aspartic acid) prepared by thermal polycondensation is presented. Experimental results of the potentiometric titration of various samples differing in the molar fraction of I and II are confronted with the results of ¹³C NMR spectroscopy. Both methods lead to comparable results.