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61.
A simple, rapid, and highly sensitive method for the detection of micro amounts of nitro compounds has been developed. Nitro compounds are reduced into corresponding hydroxylamines with zinc dust and acetic acid and coupled with diazonium chloride to give hydroxytriazines which give an intense pink to violet color with diphenylamine in acetic acid medium. Quantities of 0.1 μg or less of nitro compounds can be detected in 0.25 ml of total solution by this method. The method is free from the common interference. 相似文献
62.
Amongst various carbon sources, xylan was found to be the sole inducer of endoxylanase production by Penicillium janthinellum MTCC 10889 in submerged cultivation. Endoxylanase synthesis by a xylan induced culture was initially repressed after a simultaneous addition of xylose, probably by the inducer exclusion mechanism, but it was resumed and achieved its highest level at a much later stage of growth (at 120 h). Xylose added after 30 h of growth cannot exert its full repressive effect. Although glucose was proved to be a more potent repressor than xylose, supplementation of salicin, an alcoholic β-glycoside containing d-glucose, with pure xylan resulted in an about 3.22 fold increase in the enzyme synthesis at 72 h followed by constant high production of the enzyme at least until the 144th h of growth. Inducing capacity of salicin in a xylan induced culture was significantly reduced when it was added after 30 h of growth. Addition of salicin and xylan help to partially overcome the repressive effect of xylose and glucose. Failure of salicin in recovering the endoxylanase synthesis in actinomycin D and cyclohexamide inhibited the xylan induced culture indicating that salicin cannot initiate the de novo synthesis of the enzyme. 相似文献
63.
Prakash O Kaur H Batra H Rani N Singh SP Moriarty RM 《The Journal of organic chemistry》2001,66(6):2019-2023
The combination reagent (dichloroiodo)benzene and lead(II) thiocyanate in dichloromethane effects oxidation of various enol silyl ethers, ketene silyl acetals, and beta-dicarbonyl compounds, thereby providing an efficient and convenient method for alpha-thiocyanation of carbonyl and beta-dicarbonyl compounds. 相似文献
64.
Anita Rani Surender Kumar N. R. Bannerjee 《Fresenius' Journal of Analytical Chemistry》1987,328(1-2):33-36
Summary A Potassium ion-selective electrode based on dibenzo-18-crown-6-tungstophosphoric acid precipitate membrane is prepared and conditions for the best functioning have been investigated. The working concentration and pH-range of the electrode is 2.0×10–2 to 1.3×10–6 mol/l and 2.9–6.5, respectively. The selectivity coefficient values for a large number of cations are quite low except for caesium and ammonium ions. The electrode can tolerate non-aqueous content upto 20%.
Kaliumion-sensitive Membranelektrode auf Basis von Kronenether-Heteropolysäure相似文献
65.
66.
Hima Rani Kalita 《Tetrahedron letters》2007,48(29):5047-5049
Cuprous iodide has been found to be a very effective catalyst for allylation of aldehydes with allyltributylstannane. The catalytic system efficiently promotes the allylation reaction in DMF to produce homoallylic alcohols in high yield. 相似文献
67.
Let Гr,n—r denote the infimum of all number Г > 0 such that for any real indefinite quadratic form inn variables of type (r, n—r), determinantD ≠ 0 and real numbers c1; c2,…, cn, there exist integersx
1,x2,…,xn satisfying 0 < Q(x1+c1,x2 + c2,…,xn + cn) ≤(Г|Z > |)1/n. All the values of Гr,n—r are known except for г1,4. Earlier it was shown that 8 ≤Г1,4 ≤16. Here we improve the upper bound to get Г1,4 < 12. 相似文献
68.
The expressions for the Clark, Gazis and Wallis type of angular forces are rederived in the caseof fcc metals. These expressions are now foundtobe equivalent to the deLauney type of angular forces. 相似文献
69.
We have studied the mean free path of He fragments from projectile beams of Ar, Fe and Kr of energy 1 ? E ?2A GeV at different distances from their production point and found that they are the same, independent of their (i) energy, (ii) target size, (iii) target excitation, (iv) He multiplicities and (v) production angles. 相似文献
70.
Hard sphere diameters of liquid alkali metal alloys (Na-Cs and K-Rb) are calculated at 373 K ensuring the minimum Helmholtz
free energy of the system. These diameters are then used to fix the packing density of the alloy. On alloying, the hard sphere
diameters of Na in Na-Cs and K in K-Rb alloys expand whereas those of Cs and Rb contract. 相似文献