Toyoshi Nagai

Study of the Oxidation of Ethylenediaminetetra-Acetic Acid with Lead Dioxide Suspension in Sulphuric Acid

The stoichiometry of the reaction between lead dioxide suspension and EDTA was studied by derivative polarographic titration and determination of the products. Four moles of Pb(IV) are reduced per mole of EDTA with moderate speed at room temperature in sulphuric acid solutions. Four moles of carbon dioxide and 3 moles of formaldehyde are the products of the oxidation of 1 mole of EDTA. One mole of N-hydroxymethylethylenediamine is also thought to be produced. The overall reaction may be written as 4Pb(IV) + EDTA + 4H(2)O-->4Pb(II) + 4CO(2) + 3HCHO + H(2)NCH(2)CH(2)NHCH(2)OH + 8H(+). Ethylenediamine is also partly produced if a large excess of lead dioxide is used.

Adsorption of univalent and bivalent metal nitrates on hydrous lead dioxide Adsorption behaviour of potassium, cupric, zinc, cadmium and nitrate ions.

The individual adsorption behaviour of potassium, cupric, zinc, cadmium and nitrate ions on hydrous lead dioxide (HLD) was investigated. HLD was found to be an amphoteric ion-exchanger with an equi-adsorption point in the vicinity of pH 4.6. For bivalent metal ions, the amount of adsorption increased with pH (at pH > 3) and there was almost 100% adsorption at pH > 6. Both the adsorption capacity and the adsorption affinity on HLD were in the order copper(II) > zinc(II) > cadmium(II).

Adsorption of Bismuth on Hydrous Lead Dioxide from Bismuth-EDTA Solution

The adsorption of bismuth(III) on hydrous lead dioxide (HLD) from solutions of the bismuth(III)-EDTA complex was studied by differential pulse polarography. It was found that HLD collected bismuth quantitatively from bismuth-EDTA solution over the pH range from 1 to 12, with shaking for 1 hr, even at bismuth-EDTA concentrations as low as 10(-8)-10(-7)M. In addition, the reaction of HLD with EDTA was investigated in order to consider the participation of EDTA with respect to the adsorption behaviour of bismuth. It can be assumed that the adsorption of bismuth on HLD from bismuth-EDTA solution is correlated to the adsorptive property of HLD and to the surface redox process between HLD and EDTA.

Degradation of nitrilotriacetic acid (NTA) by oxidation with lead dioxide suspension

Degradation of nitrilotriacetic acid (NTA) by oxidation with lead dioxide suspension has been studied by differential pulse polarography. The NTA was degraded over the pH range from 4 to 9, with formation of glycine or a mixture of iminodiacetic acid and glycine. After shaking with lead dioxide for 1 hr at 30 degrees and pH ~7, the NTA was almost completely decomposed, the molar reacting ratio of Pb(IV) to NTA being ~17:1; down to 1 x 10(-5)M NTA was decomposed in a shaking time as short as 15 min and at a temperature as low as 5 degrees . The iron(III)-NTA complex was also degraded under the same conditions, and the iron released was adsorbed on the lead dioxide.

Studies of the oxidation of iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) with lead dioxide suspension in nitric acid

The stoichiometry of the oxidation of IDA or NTA with lead dioxide suspension was studied by polarographic measurement and by derivative polarographic titration. One mole and two moles of Pb(IV) are reduced per mole of IDA and NTA respectively, with moderate speed at room temperature in nitric acid solutions. One mole each of carbon dioxide, formaldehyde and glycine are produced from the oxidation of 1 mole of IDA, and two moles of carbon dioxide, two moles of formaldehyde and one mole of glycine from 1 mole of NTA. The overall reaction in each case may be written as follows: Pb(IV) + IDA + H(2)O --> Pb(II) + CO(2) + HCHO + H(2)NCH(2)COOH + 2H(+) 2Pb(IV) + NTA + 2H(2)O --> 2Pb(II) + 2CO(2) + 2HCHO + H(2)NCH(2)COOH + 4H(+).

Reduction wave of hydroxylamine in alkaline solutions at a rotating platinum electrode

Abstract The reduction wave of hydroxylamine at a rotating platinum electrode has been investigated in alkaline solutions. The unprotonated hydroxylamine gives a well-defined reduction wave at a relatively negative potential. The shape and height of the wave are influenced by the recording procedures. The wave recorded by backward scan is normal and S-shaped, corresponding to a two-electron reduction. The diffusion current is stable and is proportional to the concentration over the range 0.02–0.4 mM hydroxylamine. On the other hand, the wave recorded by forward scan is peak-shaped, and its nature is characteristic of the electrode process of the hydrogen pre-wave.

Preconcentration and separation of trace amounts of bismuth in high purity aluminium with hydrous lead dioxide.

四酢酸鉛(IV)を加水分解して得られる二酸化鉛水和物(HLD)へのAl(III)の吸着挙動を明らかにすると共に,多量Al共存下での微量Biの濃縮分離への適用性を検討した.その結果,pH2以下ではBi(III)はHLDに吸着するがAl(III)は吸着しないこと,又,BiのHLDへの吸着はかなり速く,HLDをメンブランフィルター上に保持させpH約1に調節した試料液を通常の吸引濾過する方法で,多量Al共存下でも5～100μgのBiを短時間にかつ定量的に濃縮分離でき,通常の共存物の影響もないことなどが判明した.更に,捕集後のHLDをEDTAで溶解後,EDTA-クエン酸ナトリウム複合支持電解質中で微分パルスポーラログラムを記録する方法を,標準値2ppm及び12ppmのBiを含む高純度Al系標準試料に適用し,定量値2.0及び12.2ppm,相対標準偏差3及び2%(測定回数n=5～7)の結果を得た.

Potentiometric determination of TTHA with lead tetraacetate

四酢酸鉛とトリエチレンテトラミン六酢酸(TTHA)とのキレート生成反応を用いる電位差滴定法をTTHA の定量に適用した.0.05M四酢酸鉛溶液10.00mlを含む50vol%酢酸溶液 100mlを被滴定液, TTHA溶液を滴定液とし,白金黒付き白金線電極を指示電極, 30% 硝酸カリウムを含む寒天塩橋を接続して飽和カロメル電極を参照電極として電位差滴定を行なった.電極電位は滴定液を添加して2分後に読み取った.終点は4価鉛イオンとTTHAとが2:1のモル比でキレートを生成すると思われる結果を示し,滴定曲線の終点付近での電位変化は 100mV/0.10mlであった.本滴定の結果,0.01～0.05Mの濃度範囲のTTHAを誤差±1.0%以内,相対標準偏差±0.05%で定量することができた.4価鉛イオン濃度の20% 以内の2価鉛イオンの共存は定量を妨害しなかった.被滴定溶液中の酢酸濃度,溶液の pH および温度の変化の滴定結果への影響について検討した.本滴定法は,金属指示薬法と同様に TTHA 溶液の標定法として有用であると思われる.

Polarographic Behavior of N-Bromosuccinimide at a Dropping Mercury Electrode

N-プロムコハク酸イミド(NBS)は容量分析における選択的な酸化剤として知られているが,そのポーラログラフ的挙動についてはNBSが滴下水銀電極で容易に還元されるというZumanの記述があるのみである。NBSは0.1mol/l硝酸カリウム,Britton-Robinson緩衝溶液(pH5.0)および0.01%ポリアクリルアミドを含む支持電解質溶液中で,2電子の関与する限界還元電流を示すが,電極反応生成物の臭素イオンによる水銀溶出波と混液電位を示し,そのため2段波を与える。NBSの第1波および全波の限界電流は拡散律速であり, 0V vs. SCEでのNBSの拡散電流値は4×10-3～2×10-5Nの濃度範囲で濃度に比例する。pHによるNBSの拡散電流の変化および電極水銀,ポリアクリルアミドとの反応によるNBSの分解の影響について検討した。