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weak acids
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  弱酸
     the error theory, the influence of pH values on the errors of concentration and iozization constant were investigated when measuring extra weak acids with the contant pH method. The optimum determination range of pH values have been obtained as following : pKa-0.5<pH<pKa+2.0 The experimental results were satisfactory as regards to the quantitative analysis of NH4Cl and H3BO3
     应用误差理论研究了恒pH法测定极弱酸时pH值对浓度和电离常数的误差产生的影响,给出了适宜的pH值范围:pKa-0.5<pH<pKa+2.0:对NH4Cl和H3BO3进行了实验研究.
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     Abstract A new titimetric method which is buffering titration to titrate weak acids and bases whose dissociation constants are smaller than 10 -7 is given,H_3BP_3,Na_2C_2O_4 and other compouds are titrated by the method for example,The results show that the method is simple,fast and gives a satisfactory resutts.
     对于离解常数小于10-7的弱酸弱碱,本文给出一种新的滴定分析法———缓冲滴定法对硼酸(H3BO3),草酸钠(Na2C2O4)等物质的分析表明,该法简单快速,结果令人注意。
短句来源
     It is showed through thecomputation of simulated and experimental data that weak acids and weak bases such as NaAc and(NH_4)_ 2SO_4 can be accurately determined with the method.
     用模拟数据及实验数据验证表明,本方法能够准确测定包括NaAc和(NH_4)_2SO_4在内的弱酸弱碱。
短句来源
     Determination for Dissociation Constant of Weak Acids by Metal Ion Selective Electrode
     金属离子选择电极法测定弱酸的离解常数
短句来源
     Study on the Conditions of Applying the Approximation Formula for H + Calculation on Two Mixed Monoprotic Weak Acids
     混合弱酸溶液〔H~+〕近似计算式使用条件的研究
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  弱酸根
     A novel method, incompletely suppressed conductometric detection, has been developed for the determination of anions of very weak acids.
     提出了一种新颖的用于测定极弱酸根阴离子的电导检测方法──不完全抑制电导法。
短句来源
  “weak acids”译为未确定词的双语例句
     The detection limits (S/N=3) of the organic weak acids are 0.500 μg/mL、0.145 μg/mL、0.097 μg/mL、0.195 μg/mL、1.078 μg/mLL, respectively, experiment results show that linear relationship and repeatability are good.
     弱电离物质检测限分别为 0 .5 0 0μg/ m L、0 .1 45 μg/ m L、0 .0 97μg/ m L、0 .1 95 μg/ m L、1 .0 78μg/ m L(S/ N=3 ) ,具有良好的线性关系和重现性。
短句来源
     The results show that 14.0% neutrals(including 3.6% saponifiables and 10.4% unsaponifiables),67.4% weak acids and 3.4% strong acids exist in the tall oil.
     结果表明,塔罗油中含有14.0%的中性组分(其中含有3.6%的皂化物和10.4%的不皂化物),67.4%的弱酸性组分和3.4%的强酸性组分。
短句来源
     Vibromixer deposition tests revealed that with Candida lipolytica, favorable conditions were as follows:lipase charge 5 u/g pulp, temperature 40℃,time 2h, pH7. 0. Under such conditions, the RN value (i. e. theratio of neutrals to the sum of neutrals plus weak acids)dropped from 23. 8% to 17. 8%, while 83% of theglycerides were being hydrolyzed.
     来自于Candidalipolyti-ca的脂肪酶对马尾松磨木浆进行生物控制的最佳条件是:脂肪酶用量5u/g,pH7.0、温度40℃、反应2h。 在此条件下,马尾松磨木浆树脂的RN值由初始的23.8%下降到17.8%,甘油三酸酯等酯类物质的分解率达83%。
短句来源
     Determination of the Content of the Mixed Weak Acids Via Specification Curve Method
     标准曲线法测定离解常数之比小于10~2倍的混合酸含量
短句来源
     Five new indicators for oscillopolarographic titration of very weak acids (or kases) and its salts are given. d~2E/dt~2-E curves are used.
     本文采用交流示波滴定二次微分技术(d~2E/dt~2~E)发现了5种新的碱性范围内的示波中和滴定指示剂。
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  weak acids
It was found that the exaltation phenomenon in the parallel reduction of hydrogen ions from weak acids or water is responsible for the acceleration of the electrodeposition of metals under high-voltage conditions.
      
Based on the results of systematic studies, it was demonstrated that flow-injection conductometry can be used in solutions containing amino acids for the determination of low concentrations of strong and weak acids and bases.
      
The Acid-Base Calculator program is proposed for calculating pH and ionic strength in aqueous solutions of mixtures of strong and weak acids or bases and salts.
      
A method was proposed for substantially increasing the sensitivity of the ion-chromatographic determination of weak acids by their conversion into corresponding salts on an auxiliary column with a cation exchanger in the K form.
      
The extent of acceleration defined as the ratio of the apparent permeation rate constants in the presence and in the absence of Pluronic, k/k0, was determined for 21 weak acids and bases.
      
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Purified succinic dehydrogenase is a metallo-flavin-adenine protein containing non-haematin iron.The flavin-adenine prosthetic group is firmly bound to the protein part of the enzyme and cannot be split from the latter by boiling in weak acid medium.By digesting with trypsin and chymotrypsin,however,the prosthetic group can be liberated in combination with a peptide chain.The product has been purified by a procedure which involves cresol extraction, mercuric sulphate precipitation,decomposition of the...

Purified succinic dehydrogenase is a metallo-flavin-adenine protein containing non-haematin iron.The flavin-adenine prosthetic group is firmly bound to the protein part of the enzyme and cannot be split from the latter by boiling in weak acid medium.By digesting with trypsin and chymotrypsin,however,the prosthetic group can be liberated in combination with a peptide chain.The product has been purified by a procedure which involves cresol extraction, mercuric sulphate precipitation,decomposition of the latter with hydrogen sulphide,followed by paper electrophoresis and paper chromatography.The purified product has been separated into four flavin-adenine peptides with different amino acid contents.One fraction with comparatively high mobility on paper electrophoresis and containing 12 amino acids(hydrolyzed in 6 N HCl) has an absorption spectrum with maxima at 265,350 and 450 mμ(compared with 260,375 and 450 mμ of FAD),the ratio of E_(260) and E_(450) mμ is equal to 3.87.The other three fractions has similar absorption spectra as that of the first,except for a slight shift of the 265 mμ maximum to 270 mμ.All the four flavin-adenine peptides contain cysteine and show a greenish yellow fluorescence in the u.v.light.The fluorescent intensity of the prosthetic group varies with pH and exhibits a maximum at pH 2.9.All fractions are inactive in the D-amino acid oxidase test and give on analysis 1 mole of adenine and 2.5 moles of phosphorus per mole of flavin.The pentose flavin ratio was much higher than that of FAD. Photolysis of the flavin-adenine peptides in alkaline solution yields a product which is insoluble in chloroform after acidification.Removal of the adenine results in the formation of flavin peptides.These facts indicate that the peptide chain is linked to the isoalloxazine nucleus of the prosthetic group.It is known that the absorption peak at 375 mμ of either FAD or FMN shifts to about 355 mμ at pH 12 due probably to the enolization of the keto group at the 2 or 4 position resulting in a redistribution of double bonds in the isoalloxazine ring system. In contrast our flavin-adenine peptide has the corresponding absorption maximum at 350 mμ which shows little positional shift at pH 12.This seems to suggest that the linking of the peptide chain to the isoalloxazine nucleus affects the enolization of the-NH-CO-,which may probably be the site of the linkage. The iron content increases with the specific activity of the enzyme during purification.Iron in the purified enzyme is present in the reduced state.It is firmly bound to the enzyme and can not be removed by prolonged dialysis against phosphate buffer or tris-hydroxymethyl-amino-methane buffer.Enzymatic activity is lost during prolonged incubation with o-phenanthroline or α,α'- dipyridyl and can not be recovered by incubation with Fe~(2+) or Fe~(3+).These experiments de- monstrate a close relationship between enzyme activity and the iron present in the enzyme molecule. The enzyme activity is lower in borate than in phosphate buffer.When 40 mM ethylenedi- aminetetraacetic acid is added to the borate buffer,the enzyme activity is raised almost to the level of that observed in the same concentration of phosphate buffer.The effect of EDTA and phosphate,when present together,is somewhat higher than of either alone.Alanine has a similar effect'as EDTA.

(一)用结晶胰蛋白酶及结晶胰凝乳蛋白酶处理净化的水溶性琥珀酸脱氢酶,经过对甲酚抽提,硫酸汞沉淀,硫化氢分解及纸电泳纸层析等方法净化得到四种带有不同肽链的腺嘌呤异咯嗪核苷酸。从它们的组成成份的分析以及它们的性质的观察,我们认为它们与已知的腺嘌呤异咯嗪二核苷酸略有不同。肽链是连接在异咯嗪上,其连接方式异于一般异咯嗪蛋白。肽链部份的氨基酸组成的分析结果,证明它们都含有半胱氨酸。(二)琥珀酸脱氢酶中的铁处于还原状态。铁与酶朊紧密结合,它与酶活力有密切关系。(三)无机磷可增加琥珀酸脱氢酶的活力,但琥珀酸脱氰酶的活力并不是必需依靠无机磷的存在,乙二胺四乙酸与丙氨酸也有类似无机磷的作用。

Potassium antimonyltartrate (Ⅰ) is an effective schistosomacidal agent. It would be of interest to see the activity of its corresponding pentavalent antimony derivative. Furthermore, chelation of the latter compound with various hydroxy acids would give a series of new compounds with different degree of stability, which might have some relations with their pharmacological properties. Treatment of aqueous potassium antimonyltartrate (Ⅰ) with 30% hydrogen peroxide gave the corresponding pentavalent antimonyltartrate...

Potassium antimonyltartrate (Ⅰ) is an effective schistosomacidal agent. It would be of interest to see the activity of its corresponding pentavalent antimony derivative. Furthermore, chelation of the latter compound with various hydroxy acids would give a series of new compounds with different degree of stability, which might have some relations with their pharmacological properties. Treatment of aqueous potassium antimonyltartrate (Ⅰ) with 30% hydrogen peroxide gave the corresponding pentavalent antimonyltartrate (Ⅱa). This compound is a weak acid, forms a di-potassium salt (Ⅱb) with potassium hydroxide but does not react with weak bases such as diethylamine or pyridine. Ⅱa, on boiling with potassium bitartrate, gave di-potassium antimonyl~(V) ditartrate (Ⅲ). This new compound could also be formed by the oxidation of antimony trichloride by means of hydrogen peroxide followed by chelation with tartaric acid and then neutralization with potassium hydroxide. Similar complexes were prepared by the action of glyceric acid, D-gluconic acid, mucic acid and gallic acid on Ⅱa. These new compounds are water-soluble substances, and they are suitable for injection. Preliminary pharmacological examination showed that they had quite low toxicity.

酒石酸銻鉀(Ⅰ)用过氧化氫氧化后生成相应五价銻化合物(Ⅱa),它与二乙胺或吡啶等弱碱不能成鹽,但与氫氧化鉀生成鉀鹽(Ⅱb),酒石酸銻鉀(Ⅱa)与酒石酸氫鉀、甘油酸、葡萄糖酸、半乳糖二酸及沒食子酸作用,生成相应于Ⅲ結構的螯合鹽。

The kinetic equation of polyesterification proposed by Tang is discussed from the view point of the medium effect on the ionization of weak acids, so that the ionization constant, Ke, of the reacting acid would not be a constant during the course of poly-condensation and consequently the 21/z order kinetic equation would not be valid. Experimental data show that Ke is actually a function of the extent of reaction. No appreciable conductivity is observed when the extent of reaction is over 0.65. Both...

The kinetic equation of polyesterification proposed by Tang is discussed from the view point of the medium effect on the ionization of weak acids, so that the ionization constant, Ke, of the reacting acid would not be a constant during the course of poly-condensation and consequently the 21/z order kinetic equation would not be valid. Experimental data show that Ke is actually a function of the extent of reaction. No appreciable conductivity is observed when the extent of reaction is over 0.65. Both the kinetic data of the present study and those of Flory for the polyesterification of ethy-lene glycol and adipic acid do not exactly follow the 21/2 order kinetic equation.

从弱酸电离的介貭效应讨论了唐敖庆的聚酯反应动力学方程。由于在缩聚过程中介貭性貭的改变,反应体系中羧酸的电离常数K_e不可能维持恒定,因此二级半动力学方程不能确立。实验数据说明K_e确是反应程度的函数。当反应程度在0.65以上时反应体系的电导已极小。用乙二醇与己二酸聚酯化反应得到的动力学数据并不完全符合二级半动力学方程。

 
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