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The enthalpies of formation of glycine and L-α-alanine are determined by two complementary techniques: combustion calorimetry and change of state (sublimation) calorimetry.
The values of the experimental and theoretical energy of conjugation of these two molecules (partially conjugated) and the energetical value of the C---N bond in Laidler's scheme, derived from the experimental enthalpy of atomization, are also given.
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Résumé
Les enthalpies de combustion à létat condensé de la glycine et de la L-α-alanine ont été déterminées à d'un calorìmetre isopéribolique à bombe rotative. Leurs valeurs à l'état standard à 298,15 K sont: δH°c = −(972,98±0,19) kJ mol−1 pour la glycine et ΔHδc = −(1621,45 − 0,48) kJ mol-1 pour la L-α-alanine. Les enthalpies de sublimation à l'état standard à 298,15 K ont été obtenues par calori- 相似文献12.
CaO solubility in equimolar molten salts CaCl2–x (x = 0, NaCl, KCl, SrCl2, BaCl2 and LiCl) was determined at 873–1223 K and activity coefficient calculated. CaO solubility in the binary salts is less than in CaCl2, and the activity coefficient is greater than one. With increasing temperature CaO solubility increases and the activity coefficient decreases. The dependency of CaO activity coefficient on temperature in equimolar molten salts CaCl2–x is
相似文献
| CaCl2 | RTln γCaO = 6961 + 5.06 T (K) | 1123–1223 K |
| CaCl2–NaCl | RTln γCaO = 3985 + 17.67 T (K) | 923–1123 K |
| CaCl2–KCl | RTln γCaO = 2384 + 22.72 T (K) | 1073–1223 K |
| CaCl2–SrCl2 | RTln γCaO = 27245–1.13 T (K) | 1073–1223 K |
| CaCl2–BaCl2 | RTln γCaO = 17068 + 10.19 T (K) | 1223–1273 K |
| CaCl2–LiCl | RTln γCaO = 14724 + 0.72 T (K) | 923–1073 K |
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The oxidation of glycolaldehyde with hexaquomanganese(III) ions in a noncomplexing perchloric acid medium was studied. The optimum conditions have been found for analytical use of the reaction. The recommended procedure is based on the oxidation of the test substance with the oxidant in the absence of atmospheric oxygen and back-titration of the unconsumed reagent with ferrous sulfate.
相似文献
2. Accuracy and Reproducibility of the Determination of Glycolaldehyde with Hexaquomanganese(III) Ions in a Noncomplexing Perchloric Acid Medium
| Taken (μg) | Found (μg)a | Standard deviation (μg) |
| 751 | 748 | 12 |
| 1501 | 1485 | 15 |
| 2252 | 2192 | 7 |
- a
- The values are the average of seven determinations, from which the standard deviation value was calculated.
14.
A polarographic method for the determination of antimony in lead-antimony alloys has been developed. It was found that the interference due to the presence of varying concentrations of lead and hydrochloric acid would be eliminated by the addition of potassium chloride.
t001. The method gave satisfactory results within the range:
| Hydrochloric acid | 4 — 8M | |||
| Lead | 0 — 0.03M | |||
| Antimony | 0 — 0.002M |
| SO2 (ppm) | ?HgCl2a | ?HgBr2 | ?Hg(Ac)2b | ?Hg(SCN)2 |
| 2.0 | 12,500 | 10,000 | 10,000 | 9,200 |
| 4.0 | 12,500 | 11,500 | 10,000 | 9,000 |
| 6.0 | 12,500 | 11,500 | 10,000 | 9,200 |
| 8.0 | 12,000 | 11,000 | 10,500 | 9,800 |
- a
- Molar absorptivity based on sulfite ion at 230 nm. Solution was 6.86 buffer.
- b
- Mercuric acetate solutions seemed to be somewhat unstable. absorptivity of about 25,000. The absorbance is linear over a range of approximately 0.5–5.0 ppm as SO2. Covalent mercury(II) compounds form a complex with sulfite, Hg(SO3)22?, which absorbs at 230 nm and shows a linear response over a range of 1–8 ppm as SO2.
16.
Th. Lehotkay J. Ostermeier C. Ogric F. R. Krei l 《Journal of organometallic chemistry》1996,520(1-2):59-62
η2-Phosphinocarbebe complexes of tungsten show a different behaviour towards anionic nucleophiles. The cationic η2-phosphinocarbene complex
reacts with the thiophenolate anion PhS− via carbonyl substitution, whereas the corresponding trimethylphosphine substituted carbene complex
adds the cyclopentadienyl anion at the carbene carbon atom. A third reaction pathway is observed on treating
with lithium diethylamide, providing a neutral η2-phosphinovinyl complex.
] addiert, setzt sich das Thiophenolat-Ion mit dem Dicarbonyl-substituierten Homologen
unter Carbonyl-Substitution um. In Gegenwart on Lithiumdiethylamid wird eine vergleichbare Additions- oder Substitutionsreaktion nicht beobachtet. Vielmehr findet beim Komplex
eine Deprotonierung der CCarben-Methylgruppe unter Ausbildung eines neutralen Metalla-phospha-cyclopropan-Ringes mit exocyclischer Doppelbinding statt. 相似文献
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Zusammenfassung
Kationische η2-Phosphinocarbenkomplexe des Wolframs zeigen ein differenziertes Verhalten gegenüber anionischen Nukleophilen, Während sich das Cyclopentadienyl-Anion am elektrophilen Carbenkohlenstoffatom inFull-size image
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17.
A simple, rapid, and accurate method for determination of total sulfur and inorganic sulfate in biological materials by barium chloranilate colorimetry is presented. Criteria required
3. Precision of S Determination, Whole Blood, Blood Plasma, TCA Extracts, and Urine
| Sample | Determinations | Mean (μg) | SD (μg) |
| Whole blood | 10 | 1004 | 21 |
| Blood plasma | 10 | 543 | 4 |
| TCA extracts | 10 | 24 | 2 |
| Urine (totals) | 10 | 598 | 31 |
| Urine (inorganic S) | 10 | 374.4 | 19 |
| Strippant | Cobalt stripped (%) | ||
| Na2S (M) 1.0 | 18.3 | ||
| 2.0 | 10.7 | ||
| Na2SO3 (M) 0.1 | 10.7 | ||
| 0.5 | 49.6 | ||
| 1.0 | 52.9 | ||
| EDA (%) 2.5 | 76.6 | ||
| NaOH (M) 0.1 | 4.1 | ||
| 0.5 | 74.1 | ||
| 1.0 | 90.8 | ||
| 2.0 | 76.8 | ||
| NH4OH (M) 0.1 | 24.1 | ||
| 0.5 | 91.8 | ||
| 1.0 | 97.5 | ||
| 2.0 | 99.9 | ||
| EDTA (M) 0.02 | >99.9 | ||
| 0.05 | >99.9 | ||
| 0.1 | >99.9 | ||
| EDTA (%) 0.1 | >99.9 | ||
| 0.5 | >99.9 | ||
| 1.0 | >99.9 |
| Transition metal | Concentration (M) | Percentage inhibition | Mg(II) found (×l05M) |
| Fe(II) | 3.6.10?5 | 54.1 | 4.62 |
| Fe(III) | 3.6.10?5 | 47.8 | 4.48 |
| Co(II) | 3.4.10?5 | 50.0 | 4.53 |
| Ni(II) | 3.4.10?5 | 50.0 | 4.53 |
| Cu(II) | 3.1.10?5 | 52.0 | 4.56 |
| Zn(II) | 3.0.10?5 | 54.1 | 4.62 |
| Cd(II) | 1.7.10?5 | 52.0 | 4.56 |
| Hg(II) | 9.9.10?6 | 45.8 | 4.44 |
| Sn(II) | 2.1.10?6 | 50.0 | 4.52 |
| Pb(II) | 1.2.10?6 | 54.1 | 4.62 |
- a
- Conditions: 4.53.10?5M Mg(II), 35 ng Mn ml?1, 0.429 M ammonia, 1.6.10?4M OH-PDT.
3. Determination of Magnesium in Natural Waters
| Mg(II) found (M)b | |||
| Natural water | Ca(II) presenta | Atomic absorption | |
| sample | M | Kinetic absorption | method |
| Commercial | 3.45 · 10?4 | 1.65 · 10?3 | 1.74 · 10?3 |
| Commercial | 5.46 · 10?4 | 1.57 · 10?4 | 1.81 · 10?4 |
| Untreated | 6.13 · 10?4 | 2.16 · 10?4 | 2.40 · 10?4 |
| Treated | 4.95 · 10?4 | 1.93 · 10?4 | 2.17 · 10?4 |
- a
- EDTA titration less the magnesium.
- b
- Average of three separate determinations. traces of magnesium(II). The reaction is followed spectrophotometrically by measuring the rate of change in absorbance at 594 nm. The calibration graph (percentage inhibition vs magnesium concentration) is linear in the range 329–535 · 10?5M with an accuracy and precision of 1.2%. The method has been applied to the determination of magnesium in natural waters at low concentrations.
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