Nitrogen determination in mineral oils by means of wickbold oxyhydrogen combustion

A new route for the determination of nitrogen in oil products, based on its conversion into nitrogen oxides in a Wickbold oxyhydrogen flame has been studied. A rapid method is proposed for the 15–1000 p.p.m nitrogen range; it comprises absorption of the nitrogen oxides formed (mainly nitric oxide) by sodium chlorite on an alumina, carrier and subsequent titration of the ammonia produced by Devarda reduction of the absorption mixture.     

Small gaussian basis sets for AB initio calculations on large molecules

Gaussian basis sets of (5s, 2p) for carbon, nitrogen, and oxygen, and (7s, 4p) for phosphorous and sulfur have been developed for ab initio calculations of biological molecules. Double zeta contracted bases are given for all five atoms. Minimum bases are given for carbon, nitrogen and oxygen, and a method is developed for replicating primitives in order to minimize the energy loss when contracting small bases. The contracted bases are applied to formamide and the results are compared with those obtained from other small basis sets.     

Study of the structures of indazoles,pyrazolo [3,4-b] pyridines,and pyrazolo[3,4-b]pyrazine by IR spectroscopy

It is shown on the basis of a study of the IR spectra of indazoles, pyrazolopyridines, and pyrazolopyrazine in the solid state and of their N-deutero-substituted derivatives and hydrochlorides at room temperature and at the temperature of liquid nitrogen that these heterocycles exist in a tautomeric form in which the labile hydrogen atom is localized on the nitrogen atom of the pyrazole ring. It was established that 6-aminopyrazolopyridine exists in the crystalline state in the amino form and that it is protonated at the ring nitrogen atom rather than at the amino group. The applicability of the temperature-shift method for the detection not only of NH bands but also of ND bands is demonstrated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 662–667, May, 1977.     

Determination of nitrate and nitrite in mixtures with a nitrate ion electrode

A rapid method for the determination of nitrate and nitrite ions is described. The potential of a mixture of nitrate and nitrite was measured with a nitrate ion selective electrode. The nitrite in the mixture is then oxidized to nitrate with permanganate in acid solution, and the potential of the oxidized solution is also measured with the electrode. The fundamental equations for the response of the nitrate ion electrode to nitrate ion in the presence of interfering ions were used, and a new equation was developed for calculating the original nitrate concentration of the mixture. The absolute errors for solutions of known concentrations (2.5–100 p.p.m. each) were 1.8 p.p.m. nitrate and 2 p.p.m. nitrite. When the results are calculated by computer, five determinations can be performed in 30 min. The method was applied to the determination of the oxides of nitrogen in cigarette smoke as nitrite and nitrate after dissolution in basic solution.     

Nitrogen distribution in polymers determined by proton track counting and 14 MeV neutron activation analysis

Bulk and surface nitrogen levels of compression-molded samples of polyacrylonitrile, poly (styrene-co-acrylonitrile), poly(methacrylonitrile), polycaprolactam, polyimide, and a cured epoxy resin (EPON 828 — JEFFAMINE T-403, 100:50) were determined, respectively, by 14 MeV NAA (¹⁴N(n,2n)¹³N) and by analysis of proton tracks registered in cellulose nitrate detectors (CN85) as a result of their exposure to protons from the termal neutron induced reaction,¹⁴N(n,p)¹⁴C. Except for a few polymers, agreement of results obtained for nitrogen levels in the bulk and surface regions is within expected limits. Intrinsic limitations of the method for practical determinations of nitrogen are covered. The spatial homogeneity of materials consisting of nitrogen and non-nitrogen containing segments is easily determined by image analysis of proton track densities. These data are then used to construct nitrogen distribution plots and topographical maps. The potential ability of the proton track image analysis technique for distinguishing phase separation or immiscibility of nitrogen containing polymers is discussed.     

INDIRECT ATOMIC ABSORPTION SPECTROMETRIC METHODS FOR THE DETERMINATION OF THALLIUM AND AMMONIA

Abstract

Indirect atomic absorption spectrometric methods for the determination of thallium and nitrogen (ammonia) have been developed based on the use of 12-molybdophosphoric acid as a precipitant. The molybdate obtained by dissolution of the precipitate, which is equivalent to a definite amount of thallium and/or ammonium ion, is determined by atomic absorption spectrometric measurement at 313 mμ. The optimum concentration ranges are 2 to 20 p. p. m. of thallium and 20–60 p. p. m. of nitrogen.     

Determination of nitrogen by neutron activation in meteorites and rocks

The results of determination of nitrogen content in meteorites by neutron activation are reported. The method is based on the¹⁴N(n,p)¹⁴C reaction, which occurs upon irradiation of the samples by neutrons. The use of proportional gas-filled countes for the recording of¹⁴C made it possible to obtain the low nitrogen detection limit of 0.001 g.     

Simultaneous determination of nitrogen and lithium by thermal neutron activation analysis

The determination of lithium and nitrogen in a variety of materials by thermal neutron activation is described. The nuclear reactions used are ¹⁴N(n,p)¹⁴C and ⁶ Li(n,α)³H. Radionuclides. ¹⁴C and ³H for counting are isolated by fusion of the irradiated sample in a vacuum system. Data are presented on lithium and nitrogen concentrations in several terrestrial standards. The new method allows reliable measurements on 10–50-mg samples.     

具可见光活性的氮掺杂二氧化钛光催化剂

以氮掺杂为代表的非金属掺杂型TiO₂光催化剂被誉为“第二代光催化材料”。本文首先系统评述了氮掺杂二氧化钛的制备方法,然后详细阐述了在N掺杂TiO₂研究中关于其可见光活性机制以及掺杂N在TiO₂晶格中的存在状态等方面的争议。N掺杂TiO₂粉末的制备方法主要有氨气气氛下的热处理工艺、水解沉淀法、溶胶－凝胶法以及机械化学法等;N掺杂TiO₂薄膜的制备方法主要包括磁控溅射法、脉冲激光沉积法以及金属有机化学气相沉积法等。已提出的关于N掺杂TiO₂可见光活性机制的观点有N2P与O2P能级相杂化、形成N 2p孤立能态、氧空位的作用以及具顺磁性特征的杂质敏化。关于掺杂N在TiO₂晶格中存在状态的分歧在于XPS N 1s谱中特征峰的位置及其归属的解析。文章最后指出了氮掺杂二氧化钛催化剂研究中有待解决的问题及今后的发展方向。     

Flotation of traces of heavy metals coprecipitated with aluminum hydroxide from water and sea water

Microgram quantities of heavy metals in 1-l samples of water and sea water are quantitatively coprecipitated with aluminum hydroxide at pH 9.5. The precipitate is floated with the aid of sodium oleate and small nitrogen bubbles, separated and dissolved in 2 M nitric acid, and the heavy metals are determined by atomic-absorption spectrometry. The method is rapid and applicable to 9 heavy metals at the low p.p.b. level.     

The investigation of the pore structure of silica gels with long-chain alkyl grafts by thermal analysis

The total pore volumes and the core size distributions were calculated for the silica gel Si-100 and chemically modified silica gels RP-8 and RP-18 on the basis of the thermal desorption data of various liquids. The results obtained are compared with those from the nitrogen adsorption/desorption method. Good consistency between the parameters obtained by using different methods is observed in the case of unmodified silica gel. The presence of long alkyl chains on the silica surface strongly influences the pore diameter calculated from thermogravimetric data.     

含氮药物分子中氮a-位碳氢键离解能的理论研究

本文利用G3B3 和CBS-Q高精度理论方法检验了一系列胺类有机化合物中α-碳氢键离解能的实验测量值,在此基础上筛选出(U)BHandH/6-311++G(2df, 2p)//(U)B3LYP/6-31G(d)方法,发现其可以准确快速的预测氮α-碳氢键离解能。运用该方法研究了若干含氮药物分子,发现氮α-碳氢键离解能随药物分子结构发生明显变化。为了阐明其变化规律,系统研究单取代和双取代基效应,并解释了不同取代基效应的来源。     

用激光诱导击穿光谱在空气中定量测量土壤中氮元素方法的研究-基于CN分子谱线

土壤中氮元素的快速检测在现代农业中有重要意义,传统方法前处理复杂不适合现场快速检测。激光诱导击穿光谱法已被证明可以用来对土壤中的元素进行检测,但对于土壤中的氮元素检测,如何规避大气环境中氮气的影响是不可回避的问题。提出了一种基于激光诱导击穿光谱法的空气中土壤全氮检测方法,通过对不同土壤标准样品的CN(388.3nm)分子特征谱线对比分析并建立了分析模型,结果显示,可以很好地规避大气中氮元素的影响,其检出限小于0.14%。对比于N(746.8nm)处的原子特征峰在空气中和氩气中的分析结果,其优势非常明显。     

The Structures and Stability of HNOS Isomers

Potential energy surface of HNOS system is investigated by means of MP2 method with 6-311 G(d,p) basis set.The energy for each minimum and saddle point on the potential energy surface is corrected at the QCISD(T)/6-311 G(3df,2p) level of theory with zero-point vibrational energy included.As a result ,eighteen isomers are theoretically predicted and cis-HNSO is found to be global minimum on the potential energy surface,Wherein,fourteen isomers are considered as kinetically stable species,and should be experimentally observed.Comparisons are made for HNOS system with its analogues,HNO2 and NHS2.The nature of bonding and isomers‘ stability of HNOS system are similar to HNS2.The obvious similarities and discrepancies among HNOS,HNO2 and HNS2 are attributed to the hypervalent capacity of sulfur,oxygen and nitrogen atoms.     

FeTPP和CoTPP电化学氧化还原的量子化学研究

用限制性的CNDO/2方法研究了FeTPP和CoTPP不同还原阶段的电子结构,结果表明,在FeTPP还原反应中第一个还原电子和Fe的d轨道相作用,第二个还原电子与卟啉环的4个氮原子及同它相连的8个碳原子的p轨道相作用,而CoTPP的2个还原电子与Co的d轨道相互作用,这与紫外原位光谱的实验结果完全一致。     

Structure and properties of 1-acylpyrazolines

Proton magnetic resonance spectroscopy and the method of dipole moments demonstrated that 1-acylpyrazolines exist primarily in the s-trans form, which is stabilized by the repulsion of like-charged nitrogen and oxygen atoms. Simultaneous reduction of the C =O and C =N bonds was observed during the action of lithium aluminum hydride on 1-formyl-and 1-trifluoroacetylpyrazolines, which is explained by the relatively high polarity of the C=N bond.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 488–491, April, 1972.     

Infrared macro and semimicro determination of nitrogen in raw nitrocellulose and nitrocellulose contained in propellants

The infrared procedure for the determination of nitrogen in raw nitrocellulose has been improved. In the original method 0.31-0.32 g of sample was dissolved in 45 ml of tetrahydrofuran, the solution was weighed, and the infrared peak at 6.0 microm was measured. The calibration curve was prepared by plotting absorbance against mg of nitrogen per g of solution. The method has the disadvantage that the height of the peak is affected by the sample weight. In the improved method the error due to the sample weight is eliminated by using 0.3000 g of sample and diluting to 50 ml in a volumetric flask. The calibration curve is prepared by plotting absorbance against % nitrogen. The method was extended to the semimicro scale by using a 30.0-mg sample and diluting to 5 ml in a volumetric flask. The method has been applied on the macro and semimicro scales to the direct determination of nitrogen in nitrocellulose after a methylene chloride extraction. The amounts of graphite and inorganic salts found in nitrocellulose-base propellants do not interfere, but a correction must be made to refer the results to 0.3000 g of nitrocellulose for the macro method or 30.0 mg of nitrocellulose for the semimicro method. The same calibration curve is used for all procedures.     

Optical method for measuring thermal accommodation coefficients using a whispering-gallery microresonator

A novel optical method has been developed for the measurement of thermal accommodation coefficients in the temperature-jump regime. The temperature dependence of the resonant frequency of a fused-silica microresonator's whispering-gallery mode is used to measure the rate at which the microresonator comes into thermal equilibrium with the ambient gas. The thermal relaxation time is related to the thermal conductivity of the gas under some simplifying assumptions and measuring this time as a function of gas pressure determines the thermal accommodation coefficient. Using a low-power tunable diode laser of wavelength around 1570 nm to probe a microsphere's whispering-gallery mode through tapered-fiber coupling, we have measured the accommodation coefficients of air, helium, and nitrogen on fused silica at room temperature. In addition, by applying thin-film coatings to the microsphere's surface, we have demonstrated that accommodation coefficients can be measured for various gases on a wide range of modified surfaces using this method.     

Depth distribution of light elements in heavy matrices with charged-particle-induced reactions

Two different methods are described for measuring the depth distribution of carbon, nitrogen and oxygen in metals: Proton activation makes use of resonances in the excitation function of the (p, γ) reactions for depth determination, and with the aid of the different half-lives for for β⁺-decay provides information on the different constituents present. The other method makes use of the shape of neutron groups in the time-of-flight spectra from deuteron-induced reactions. Depths of some tens of microns with a resolution of fractions of a micron are studied. The detection limit is of the order of 100 ppm.