Weak bases in strong acids. III. Heats of ionization of amines in fluorosulfuric and sulfuric acids. New general basicity scale

1970 ◽  
Vol 92 (5) ◽  
pp. 1260-1266 ◽  
Author(s):  
Edward M. Arnett ◽  
Roderic P. Quirk ◽  
John J. Burke
Keyword(s):  
Weak Bases ◽  
Strong Acids

scholarly journals Utilization of Kalpataru Flower Extract (Hura crepitans Linn) as an Alternative Acid Base Indicator

2020 ◽  
Vol 9 (3) ◽  
pp. 148-157
Author(s):  
Bayu Riswanto ◽  
Sitti Aminah
Keyword(s):  
Strong Acid ◽  
Weak Acids ◽  
Acid Base ◽  
Flower Extract ◽  
Weak Bases ◽  
Base Solution ◽  
Acid Base Titration ◽  
Hura Crepitans ◽  
Dark Green ◽  
Strong Acids

Kalpataru flower (Hura crepitans Linn) is an anthocyanin-containing plant. This study aims to utilize extract from the kalpataru flower as an alternative acid base indicator and determine the type of acid-base titration suitable for extracting the kalpataru flower indicator. Kalpataru flowers are macerated with methanol solvent for around 2 hours. Kalpataru flower extract was tested as an indicator in acid-base solution, buffer, and compared with phenolphthalein and methyl orange for acid-base titration, namely: strong acids with strong bases, weak acids with strong bases, and weak bases with strong acids. The results obtained in this study were: indicator extract of brownish yellow kalpataru flowers, in strong red acids, in strong bases of dark green, in weak pink acids, and in weak bases in light green. In the buffer, the indicator extract of the kalpataru flower has a range of pH pH 4-5 (pink-colorless) and pH 9-11 (yellowish green-dark green). The indicator of kalpataru flower extract can be used on strong acid titration with strong bases, weak acids with strong bases and weak bases with strong acids. Kalpataru flower extract can be used as an acid-base indicator.

scholarly journals Kemampuan Siswa Memperoleh dan Memahami Konsep Hidrolisis Garam dalam Pembelajaran Menggunakan LKS Berbasis Belajar Penemuan pada Siswa Kelas XI SMAN 2 Palangka Raya Tahun Ajaran 2018/2019

2020 ◽  
Vol 1 (1) ◽  
pp. 16-29
Author(s):  
Riska Meilani Simanjuntak ◽  
Abudarin Abudarin ◽  
Karelius Karelius
Keyword(s):  
Discovery Learning ◽  
Research Subjects ◽  
Descriptive Research ◽  
Comprehension Test ◽  
Weak Bases ◽  
Three Stages ◽  
Strong Acids ◽  
Academic Year ◽  
Hydrolysis Of

Materi larutan merupakan materi yang sulit bagi kebanyakan siswa, salah satunya materi hidrolisis garam. Penelitian ini bertujuan untuk mendeskripsikan kemampuan siswa memperoleh dan memahami konsep hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan. Penelitian ini merupakan penelitian deskriptif. Subyek penelitian adalah siswa kelas XI MIPA SMA Negeri 2 Palangka Raya tahun ajaran 2018/2019 yang berjumlah 36 siswa. Instrumen yang digunakan berupa soal tes pemahaman konsep (pretes dan postes) dan LKS berbasis belajar penemuan. Data dikumpulkan melalui tiga tahap, yakni pretes, pelaksanaan pembelajaran, dan postes. Hasil penelitian menunjukkan bahwa kemampuan siswa dalam memperoleh konsep hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan tercermin dari jumlah siswa yang memperoleh konsep, yaitu rata-rata sebesar 82,64%. Pemahaman konsep siswa tentang hidrolisis garam dari asam kuat dan basa lemah dalam pembelajaran menggunakan LKS berbasis belajar penemuan rata-rata sebesar 89,81%.   Solution material is a difficult material for most students, one of which is salt hydrolysis. This study aims to describe the students' ability to obtain and understand the concept of salt hydrolysis from strong acids and weak bases in learning using discovery learning based worksheets. This research is a descriptive research. The research subjects were students of class XI MIPA at SMA Negeri 2 Palangka Raya in the 2018/2019 academic year, totaling 36 students. The instruments used were in the form of concept comprehension test questions (pretest and posttest) and discovery learning-based worksheets. Data were collected through three stages, namely pretest, implementation of learning, and posttest. The results showed that the students' ability to obtain the concept of hydrolysis of salt from strong acids and weak bases in learning using discovery learning-based worksheets was reflected in the number of students who obtained the concept, namely an average of 82.64%. Students' understanding of the concept of salt hydrolysis from strong acids and weak bases in learning using discovery-based worksheets an average of 89.81%.

NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: II. AMIDES, THIOAMIDES, AND SULPHONAMIDES

1963 ◽  
Vol 41 (10) ◽  
pp. 2642-2650 ◽  
Author(s):  
T. Birchall ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Carbonyl Oxygen ◽  
Conclusive Evidence ◽  
Sulphur Atom ◽  
Magnetic Resonance Studies ◽  
Weak Bases ◽  
Strong Acids ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of solutions of amides in fluorosulphuric acid confirm previous results which indicated that protonation of amides occurs on the carbonyl oxygen. A similar study of solutions of thioacetamide, thioacetanilide, thiourea, and N-methylthiourea provides conclusive evidence that the sulphur atom is protonated in these bases. In the case of N-methyl- and N,N′-dimethyl-p-toluenesulphonamide and sulphamide protonation occurs on nitrogen rather than on oxygen. It was not possible to obtain any conclusive evidence on the site of protonation of urea and N,N′-dimethylurea. Evidence is presented which indicates that thiourea and N-methylthiourea are diprotonated in solution in strong acids such as fluorosulphuric acid, and diprotonation of urea and N,N′-dimethylurea under the same conditions also seems very likely.

scholarly journals THE SIGNIFICANCE OF THE HYDROGEN ION CONCENTRATION FOR THE DIGESTION OF PROTEINS BY PEPSIN

1920 ◽  
Vol 3 (2) ◽  
pp. 211-227 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Enzyme Preparation ◽  
Proteolytic Enzymes ◽  
Quantitative Agreement ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Enzyme Preparations ◽  
Weak Bases ◽  
Strong Acids ◽  
Hydrolysis Of

The experiments described above show that the rate of digestion and the conductivity of protein solutions are very closely parallel. If the isoelectric point of a protein is at a lower hydrogen ion concentration than that of another, the conductivity and also the rate of digestion of the first protein extends further to the alkaline side. The optimum hydrogen ion concentration for the rate of digestion and the degree of ionization (conductivity) of gelatin solutions is the same, and the curves for the ionization and rate of digestion as plotted against the pH are nearly parallel throughout. The addition of a salt with the same anion as the acid to a solution of protein already containing the optimum amount of the acid has the same depressing effect on the digestion as has the addition of the equivalent amount of acid. These facts are in quantitative agreement with the hypothesis that the determining factor in the digestion of proteins by pepsin is the amount of ionized protein present in the solution. It was shown in a previous paper that this would also account for the peculiar relation between the rate of digestion and the concentration of protein. The amount of ionized protein in the solution depends on the amount of salt formed between the protein (a weak base) and the acid. This quantity, in turn, according to the hydrolysis theory of the salts of weak bases and strong acids, is a function of the hydrogen ion concentration, up to the point at which all the protein is combined with the acid as a salt. This point is the optimum hydrogen ion concentration for digestion, since the solution now contains the maximum concentration of protein ions. The hydrogen ion concentration in this range therefore is merely a convenient indicator of the amount of ionized protein present in the solution and takes no active part in the hydrolysis. After sufficient acid has been added to combine with all the protein, i.e. at pH of about 2.0, the further addition of acid serves to depress the ionization of the protein salt by increasing the concentration of the common anion. The hydrogen ion concentration is, therefore, no longer an indicator of the amount of ionized protein present, since this quantity is now determined by the anion concentration. Hence on the acid side of the optimum the addition of the same concentration of anion should have the same influence on the rate of digestion irrespective of whether it is combined with hydrogen or some other ion (provided, of course, that there is no other secondary effect of the other ion). The proposed mechanism is very similar to that suggested by Stieglitz and his coworkers for the hydrolysis of the imido esters. Pekelharing and Ringer have shown that pure pepsin in acid solution is always negatively charged; i.e., it is an anion. The experiments described above show further that it behaves just as would be expected of any anion in the presence of a salt containing the protein ion as the cation and as has been shown by Loeb to be the case with inorganic anions. Nothing has been said in regard to the quantitative agreement between the increasing amounts of ionized protein found in the solution (as shown by the conductivity values) and the amount predicted by the hydrolysis theory of the formation of salts of weak bases and strong acids. There is little doubt that the values are in qualitative agreement with such a theory. In order to make a quantitative comparison, however, it would be necessary to know the ionization constant of the protein and of the protein salt and also the number of hydroxyl (or amino) groups in the protein molecule as well as the molecular weight of the protein. Since these values are not known with any degree of certainty there appears to be no value at present in attempting to apply the hydrolysis equations to the data obtained. It it clear that the hypothesis as outlined above for the hydrolysis of proteins by pepsin cannot be extended directly to enzymes in general, since in many cases the substrate is not known to exist in an ionized condition at all. It is possible, however, that ionization is really present or that the equilibrium instead of being ionic is between two tautomeric forms of the substrate, only one of which is attacked by the enzyme. Furthermore, it is clear that even in the case of proteins there are difficulties in the way since the pepsin obtained from young animals, or a similar enzyme preparation from yeast or other microorganisms, is said to have a different optimum hydrogen ion concentration than that found for the pepsin used in these experiments. The activity of these enzyme preparations therefore would not be found to depend on the ionization of the protein. It is possible of course that the enzyme preparations mentioned may contain several proteolytic enzymes and that the action observed is a combination of the action of several enzymes. Dernby has shown that this is a very probable explanation of the action of the autolytic enzymes. The optimum hydrogen ion concentration for the activity of the pepsin used in these experiments agrees very closely with that found by Ringer for pepsin prepared by him directly from gastric juice and very carefully purified. Ringer's pepsin probably represents as pure an enzyme preparation as it is possible to prepare. There is every reason to suppose therefore that the enzyme used in this work was not a mixture of several enzymes.

Juglone and Lawsone as Acid-Base Indicators

1977 ◽  
Vol 32 (8) ◽  
pp. 890-892 ◽  
Author(s):  
Krishna C. Joshi ◽  
P. Singh ◽  
G. Singh
Keyword(s):  
Weak Acids ◽  
Acid Base ◽  
Natural Sources ◽  
Ph Values ◽  
End Point ◽  
Weak Bases ◽  
Strong Acids

Juglone and lawsone, both acid-base indicators, obtained from natural sources and give pink and red colours with aqueous alkalies, respectively. Their transition ranges are found to be pH 7.4–8.2 and 2.6–3.4. To establish the transition intervals, a buffer series ranging in the pH values from 2.0–2.2–2.4–2.6–2.8–3.0–3.2–3.4–3.6–3.8–4.0–4.2–4.4–4.6–4.8–5.0–5.2–5.4–5.6–5.8–6.0–6.2–6.4–6.6–6.8–7.0–7.2–7.4–7.6–7.8–8.0–8.2–8.4–8.6–8.8–9.0 has been used. Juglone can be used for the titrations of strong acids with strong bases and weak acids with strong bases and lawsone can be used for the titration of strong acids with weak bases only. Permanancy of the colours at the end point is one of their advantages.

On-Column Periodate Reaction Method for Analysis of Ephedrine Sulfate in Solid Dosage Forms: Collaborative Study

1980 ◽  
Vol 63 (4) ◽  
pp. 692-695
Author(s):  
Charles C Clark ◽  
◽  
W Brittan ◽  
C Hezeau ◽  
D Hughes ◽  
...  
Keyword(s):  
Collaborative Study ◽  
Dosage Forms ◽  
Water Soluble ◽  
Solid Dosage Forms ◽  
Commercial Sample ◽  
Reaction Method ◽  
Solid Dosage ◽  
Weak Bases ◽  
Strong Acids

Abstract Seven laboratories collaboratively studied a method for the quantitative ultraviolet (UV) determination of ephedrine sulfate in solid dosage forms. Ephedrine is separated from water-soluble impurities and strong acids by elution from a weakly basic Celite column, and further cleaned up by retention on a weakly acidic column while the weak acids, weak bases, and organic-soluble neutrals are eluted. Ephedrine is eluted from the column after neutralization with NH3 and is converted to benzaldehyde via an on-column periodate reaction. The samples collaboratively studied consisted of 3 synthetic preparations of known ephedrine sulfate concentrations and 2 commercial preparations containing ephedrine sulfate. One commercial sample was submitted as a blind duplicate. Recoveries for the synthetic preparations averaged 101.7, 101.2, and 100.5% for mixtures containing 7.93, 9.35, and 6.85% ephedrine sulfate, respectively. The means and standard deviations for the commercial preparations were 24.72 ± 0.376 mg/dosage unit for the preparation labeled to contain 25 mg/dosage unit, and 22.46 ± 0.643 and 22.29 ± 0.339 mg/dosage unit for the blind duplicate labeled to contain 24 mg/dosage unit. The method has been adopted as official first action.

How Are Strong Acids or Strong Bases Substituted by Weak Acids or Weak Bases in Aerosols?

2020 ◽  
Author(s):  
Zhe Chen ◽  
Na Wang ◽  
Shu-Feng Pang ◽  
Yun-Hong Zhang
Keyword(s):  
Organic Acid ◽  
Gas Phase ◽  
Atmospheric Aerosols ◽  
Aerosol Particles ◽  
Volatile Acid ◽  
Weak Acids ◽  
Weak Bases ◽  
Chloride Depletion ◽  
Nitrate Depletion ◽  
Strong Acids

<p>Due to significant influence on global climate and human health, atmospheric aerosols have attracted numerous interests from the atmospheric science community. To provide insight into the aerosol effect, it is indispensable to investigate the aerosol properties comprehensively.</p><p>Since atmospheric aerosols are surrounded by substantial gas phase and have high specific surface area, the composition partitioning between particle phase and gas phase must be considered as a key aerosol property, which is termed as volatility for volatile organic/inorganic components. Recent studies show that the aerosol volatility can also be induced by the reaction of components in addition to the volatile compositions. Herein, we summarize four types of volatility induced by reaction, namely chloride depletion, nitrate depletion, ammonia depletion and volatility induced by salt hydrolysis. For chloride depletion and nitrate depletion, these processes can be regarded as reactions that strong acids are substituted by weak acids. The high volatility of the formed HCl or HNO<sub>3</sub> drives the reaction continuously moving forward.</p><p>For ammonium depletion, we observed the reaction occurs between (NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> and organic acid salts during dehydration process by ATR-FTIR. For example, when molar ratio is 1:1, significant depletion of ammonium was observed in the disodium succinate/(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> particles, indicating the evaporation of NH<sub>3</sub>. Besides, the hygroscopicity of the aerosol particles decreased after the dehydration, which should be attributed to the formation of less hygroscopic succinic acid and ammonium depletion. By regarding organic acid salts as weak bases, the ammonium depletion is a reaction that strong base substituted by weak base, driving by the continuous release of NH<sub>3</sub>. In addition to volatility induced by reactions within multi-component aerosols, we also found that the salt hydrolysis can also cause the formation of volatile product. For magnesium acetate (MgAc<sub>2</sub>) aerosols, we found significant water loss of the aerosol particles under constant relative humidity condition, while the amount of acetate was also decreased. We infer that the acetic acid (HAc) evaporation is caused by the hydrolysis of MgAc<sub>2</sub>, leading to the volatility and declined hygroscopicity. Two factors contribute to the volatility of MgAc<sub>2</sub> aerosols. One is the volatile acid donner (Ac<sup>2-</sup>), which can lead to the formation of volatile HAc. The other is the residual ion accepter (Mg<sup>2+</sup>), which can combine residual OH<sup>-</sup> after the proton is depleted by the evaporation of HAc. The formation of insoluble Mg(OH)<sub>2</sub> effectively maintains the aqueous pH in a suitable range, keeping the reaction moving forward. It should be noted that the co-exist of volatile acid donner and residual ion accepter is indispensable for the volatility induced by hydrolysis.</p><p>Generally, for the volatile species present in atmosphere, the aerosol volatility induced by the reaction of components can be an important pathway for their recycling processes. Due to the substantial composition modification, the hygroscopicity is also affected by such reaction. Therefore, this partitioning behavior of aerosols needs to be considered in the future atmospheric aerosol study, which may prevent the underestimate of particle volatilization or overestimate of hygroscopicity.</p>

Collaborative Study of an On-Column Periodate Reaction Method for the Analysis of Phenylpropanolamine Hydrochloride in Elixirs

1973 ◽  
Vol 56 (1) ◽  
pp. 100-104
Author(s):  
Charles C Clark
Keyword(s):  
Collaborative Study ◽  
Water Soluble ◽  
Weak Acids ◽  
Reaction Method ◽  
Weak Bases ◽  
Phenylpropanolamine Hydrochloride ◽  
Standard Deviations ◽  
Strong Acids

Abstract Twelve laboratories collaboratively studied a method for the quantitative UV determination of phenylpropanolamine HC1 in elixirs. The phenylpropanolamine is separated from water-soluble impurities and strong acids by elution from a weakly basic Celite column. Further cleanup is accomplished by retention of the phenylpropanolamine on a weakly acidic column while the weak acids, weak bases, and organic-soluble neutrals are eluted. Phenylpropanolamine is eluted from the column after neutralization with NH3 and is converted to benzaldehyde via an on-column periodate reaction. The samples collaboratively studied consisted of 2 commercial and 2 synthetic elixirs. Recoveries of the synthetic elixirs averaged 100.1 and 101.8% for mixtures containing 5.05 and 12.52 mg/5 ml phenylpropanolamine HC1, respectively. The means and standard deviations for the commercial preparations were 4.75 ±0.12 and 12.34±0.16 mg/5 ml. The method has been adopted as official first action.

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