VOLUME 8, NO4, DEC 1986

A Differential Amplifier based Autoconductometric Estimation Method for Strong/Weak Acid-Base Systems

An autoconductometri c est i ma ti on method is introduced based on the recordi ng of oscill a tory current i mpu 1 ses, generated duri ng neutral i za t ion events, in an unbalanced Wheatstone bridge coupled to a Wein oscillator. Toe re 1 evant e lectroni c ci rcuitory and experi menta 1 set-up is fabri cated from inexpensive, locally available components. The performance of the proposed method is checked on sixteen strong/weak acid-base neutralization systems. The overall average error of the method is rated at ± 1.5% with a precision of ± 0.5% for duplicate measurements. The data are discussed in specific relation to lower detection limit, sensitivity and electrolytic flow rates.read more

---

S S AKHTAR ,M JAFFAR ,

ALKYLATION OF HYDROXYPYRONES

A procedure for the alkylation of hydroxypyrones with alkyl halides in the presence of potassium hydroxide in dimethyl sulphoxide (DMSO) at ambient temperature has been described. The method supercedes in simplicity and efficiency to those previously reported. The alkylation has been found to be very effective especially with methyl or ethyl iodide or benzyl bromide. To prove the general applicability of the method some related 4­hydroxycoumarins have also been alkylated.read more

---

M IQBAL ,M SIDDIQ ,M A MUNAWAR ,

Nitration of Aromatic Compounds with Potassium Nitrate in Polyphosphoric Acid

A variety of aroma ti c compounds were subjected to nitrati on usi ng potassium nitrate in polyphoshoric acid. The method was found useful to obtAin single nitro - product in each case. The position of nitration in the aromati c' substrate was found to depend on the nature of the substitutent already present.read more

---

M M ASLAM ,R IQBAL ,

A NEW SPECTROPHOTOMETRIC DETERMINATION OF URANYL-ION WITH PARA-CHLOROTRIFLUOROBENZOYL ACETONE

A new colorimetric estimation of uranyl ion is described. The pro­cedure involves the reaction of uranyl ion with p-chlorotrifluobenzoyl acetone in acetonic medium. The condition for analytical measurement is given too. Corrmon cations that might interfere are studied. < Detection limit and reproducibility are given to evaluate the applicability of this method.read more

---

G Y MATTI ,T A K NASSER ,

STUDIES INVOLVING LABILE VITAMIN-B1 METAL-COMPLEXES .3. PREPARATION AND GENERAL MECHANISM FOR THE FORMATION OF COMPLEXES OF THE GENERAL FORMULA-M-STAR (NH3)6MX5

Reactions of labile Vitamin 81 metal com~lexes, thiaminium tetrachlo­romercurate (II) monohydrate, Hg(Th)C14.H20, thiaminium tetrachlorocadmate (II) monohydrate, Cd(Th)C14.H20 and thiaminium tetrachlorozincate(ll) mono­hydrate, Zn(Th)C14.H20 with hexammineruthenium(lll) chloride, Ru(NH3)6C13 in aqueous medium (1:1 molar ratio) yielded hexammineruthenium (III) pentachlo­romerucrate(II), Ru(NH3)6H9C1S' hexammineruthenium(lll) pentachlorocadmate (II),Ru(NH3)6CdC1S and hexammineruthenium(lll) pentachlorozincate(II),Ru(NH3)6ZnC15'respectively. These new compounds have been characterized by elemental analyses and irifrared spectra. The rationale for the particular geometry assumed by each of the HgC1S ,CdC1S and ZnC1S complex ions is discussed.read more

---

A ADEYEMO ,

EFFECT OF ORGANIC-SOLVENTS ON THE ATOMIC-ABSORPTION OF TIN IN AIR HYDROGEN FLAMES .1

The effect of organi c so 1 vents on tion absorption in air-hydrogen flames has been investigated. In present studies the effect of organic solvents found depended very much on the fuel/oxidant ratio of the flame. It has been found that solvents increased the tin absorption in fuel-lean flames while in fuel-rich flames they depress it. These studies sign~ficantly extend the present knowledge of behaviour of tin atoms in air-hydrogen flames. In this part of work the effect has been established by using various sovlents, flames and metals and by changing other parameters such as flame height etc.read more

---

I L MARR ,J ANWAR ,

Surface Characterization Including Surface area measurements of the Chromatographic Silica gel

Structural system of silica gel has been investigated by adsorption techniques and Electron Microscopy. The gel is highly porous and primarily composed of large irregular grains which are disorderly arranged, constitu­ting the voids. Heat treatment shrinks the material of the gel on the expense of bound water. Most of the surface area and pore volume lie in the small pores with hydraulic radii than 20oA.read more

---

M KHAN ,M AFZAL ,

Indirect Determination of Nitrate by Spectrophotometry

A relatively simple and sensitive method for the determination of nitrate has been developed. The method is based on the reduction of nitrate with mercury sulphuric acid mixture. Oxidized mercury is determined spectro­photometrically by dithizone method. Various parameters such as volume and concentration of sulphuric acid, effect of other anions and effect of time have been checked. The method is found equally useful for organic and inorga­nic nitrates.read more

---

Z U NISA ,M I FAROOQI ,J ANWAR ,

A CONVENIENT ROUTE FOR BUTYROLACTONE SYNTHESIS

l,l-Diaryl-ethylene oxides(Ia-c) react with ethyl cyanoacetate or malononitrile and ethyl aceto-acetate in the presence of sodium ethoxide to give y,y-diaryl-a-cyano(IIa-c) and y ,y-diaryl-a-aceto(IIIa-c)-y-butyrolac­tones, respectively. Alkaline hydrolysis of II afforded the corresponding a-carboxy-y-butyrolactones(IVa-c). Decarboxylation of IV yieldedy,y-diaryl­y-butyrolactones(Va-c). Also, (la-c) react with sodioacetylacetone to give 3-acetyl-S,S-diaryl-S-hydroxy-2-pentanones(Vla-c). The structure elucidation of the products is based on chemical transformations, spectral and chemical data.read more

---

G E MOUSSA ,M E SHABAN ,M M SAAD ,

A Kinetic Method for the Spectrophotometeric Determination of Cobalt using Flow Injection Analysis

A flow injection manifold for the rapid and sensitive determination of cobalt(II) is described, based on its catalytic effect on the oxidation of Alizarin Red S (1,2-dihydroxy-anthraquinone-3-sulphonic acid) by hydrogen  peroxide in alkaline media. The limit of detection is 10-7M (6 pmol) at a -1 -7 sample throughput of 60 h with a c.v. of 1.9% for 10 M cobalt and 0.3% for 10-5M cobalt.read more

---

A NABI ,P J WORSFOLD ,