no 1
L. Michaelis 1 and his coworkers have extended the number 1 L. Michaelis and A. Gyemant Biochem. Z., 109, 165 1920 . L. Michaelis and A. Kr ger Biochem. Z 119, 307 1921 . of valuable nitrophenols. These indicators are extremely useful for determining the pH of unbuffered solutions. The preparation of these substances is described in detail in the original publications of Michaelis and Gyemant 1 and of Michaelis and Kr ger. The paper of I. W. Kulikow and S. W. Panowa 2 should be consulted for...
choh H chohh BaseAcid
By the hydrogen ion concentration in an ammonia solution we mean the concentration of ammonium ion NH44 Qualitatively, therefore, the ammonium ion should have the same properties as the hydroxonium ion. Actually A. Volmer 2 has shown by R ntgen analysis a striking crystallographic similarity between the ammonium ion in ammonium Perchlorate NH4CIO4 and the hydroxonium ion in hydroxonium Perchlorate H3OCIO4. Almost thirty years ago A. Hantzsch 3 had demonstrated that the cryoscopic effect of...
ch
Melting point 250 . Lactone form colorless. 1 A. Thiel and R. Diehl Sitzb. Ges. Naturw. Marburg, 62, 471 1927 . A. Thiel and L. Jungfer Z. anorg. allgem. Chem., 178, 49 1929 . A. Thiel Monatsh., 63 54, 1008 1929 . The commercial product may be purified by recrystallization from methyl or ethyl alcohol. The stock solution should contain 0.1 of the indicator in a 60 alcohol solution. As is the case with all single-color indicators, the transformation interval will depend upon the concentration of...
chcooh chcoo CHCOOH chcoo
In neither of these cases is water produced by the '' neutralization ' and not even salt is formed in the last reaction. The formation of salt occurs only in reactions between neutral acids and bases. It seems surprising at first to refer to water as a base. This is probably due to the fact that we have always considered the hydrogen ion concentration in water identical with the hydroxonium concentration, and because the dissociation constant of water as well as of other solvents is exceedingly...
CioHeOH CioHeOH
S. P. L. Sorensen and S. Palitzsch 1 first introduced this indicator which they prepared according to the directions of Grabowski. A. Thiel 2 states that the compound possesses a more or less distinct rose color, depending upon the degree of its purity. Hence the color change has been described as either from rose to blue or from a faint yellow-rose to green. After considerable purification, Thiel finally succeeded in obtaining a practically white product. He concluded from this that commercial...
nnchno
Aqueous stock solutions may contain 0.1 of the indicator, 1-3 drops being required per 10 c.c. The transformation is from yellow to violet in the region 10.2-12.0. This compound is well suited for colorimetric determinations. Azo violet o-p-Dihydroxyazo-p-nitrobenzene, This substance was prepared by K. Suitsu and K. Okuma 1 who recommended its use as a reagent for magnesium. I. M. Kolt-hoff 2 demonstrated the acid-base indicator properties of the compound. Stock solutions should contain 0.1 of...
The determination of dissociation constants
Most dissociation constants recorded in the literature 1 have been calculated on the basis of the old dissociation theory of Arrhenius. It is therefore of great practical interest to evaluate these data critically and to see how the thermodynamic dissociation constants may be calculated from them. Only the three most important methods for determining dissociation constants will be discussed. Sufficient information has been given 1 For a summary, cf. Landolt-B rnstein-Roth...
Ion product and ion activity product of water
Applying the mass action law to the equilibrium between hydrogen and hydroxyl ions In the absence of solute, the activity of water aH20 may be set equal to unity in the conventional manner and even in dilute solutions, the activity is not far removed from this value. The activity of water in more concentrated solutions can be calculated from water vapor pressure measurements where p is the vapor pressure of the solution and p0 is that of pure water at the same temperature. Taking aH20 1, then
cchoh
This compound is insoluble in water, but dissolves in sulfuric acid with a dark red color, and in concentrated hydrochloric acid with an orange-yellow color. In alkaline solution it is blue. Orndorff and Wang have prepared the crystalline hydrochloride, sulfate, and perchlorate of this substance. The Methoxytriphenylcarbinols. The methoxytriphenylcarbi-nols are derivatives of triphenylcarbinol, which behaves as a weak base. Hakon Lund 3 has prepared and studied intensively a number of such...
Info 1
H X OH- Kw, A H A- OH- , A A A- c. From 1 and 2 we have J. Walker 1 derived this equation in a similar manner. There are two unknowns, H and A , in equation 8 and a direct solution is not possible. S. P. L. Sorensen 2 has eliminated the unknown A and obtained the expression This equation is too inconvenient for practical use. Its general solution can not be given. The author, therefore, suggests that equation 8 be used in calculations, assuming as a first approximation that the concentration...
AocMao
in which jul is the viscosity. The degree of dissociation calculated from electromotive force data is fa, and 0 denotes the dissociation found from freezing point lowering. 1 Storch Z. physik. Chem., 19, 13 1896 . Van't Hoff Z. physik. Chem., 18t 300 1895 . 2 Noyes and McInnes J. Am. Chem. Soc., 42, 239 1920 . c A. A. Noyes has pointed out a number of other objections to the theory of Arrhenius. It is difficult to understand, for example, why a normal hydrochloric acid solution should show an...
h ni
This substance behaves like a weak base, is insoluble in water, and dissolves in dilute hydrochloric acid as a colorless salt. The indicator properties were investigated by I. M. Kolthoff.1 Stock solution a 0.1 in 70 alcohol red solution . Stock solution b 0.1 neutralized solution prepared by dissolving 100 mg. of indicator in 40 c.c. of alcohol, adding 1.9 c.c. of 0.1 N hydrochloric acid, and diluting to 100 c.c. with water. This solution has a weak violet color and is stored in Jena or Pyrex...
pH pKi
According to 4 and 5 , the change commences at a pH less than pKi by one unit, and is practically complete at a pH in excess of pKi by the same amount. The transformation range of this indicator thus includes two units of hydrogen exponent. This range of two pH units happens to be characteristic of most indicators. As regards the visibility of the acid form in the presence of the alkaline, similar relationships obtain and the production of the colored form in visible quantities starts at a...
Selected list of useful indicators
A compilation of indicators useful for pH determinations was made available first by the laboratory of W. Nernst. Simultaneous reports by W. Salessky,4 H. Friedenthal,5 and B. Fels 6 appeared in 1904. Salm 7 made a noteworthy contribution by 1 N. Bjerrum Die Theorie der alkalimetrischen und acidimetrischen Indicatoren, Sammlung Herz, 1914, 30. 2 W. M. Clark and Lubs J. Bact., 2, 110 1917 J. Biol. Chem., 25, 479 1916 . 8 J. F. McClendon J. Biol. Chem., 54, 647 1922 . 4 W. Salessky Z....
The theory of complete dissociation of strong electrolytes
In spite of the various obvious objections to the Arrhenius theory, it remained the basis for the electrochemistry of solutions until 1923, simply because no better theory had replaced it. At the end of the preceding century a number of authors, among them 0. Jahn,1 had demonstrated indeed that the theory did not represent the facts in a satisfactory manner. As early as 1894, J. J. van Laar 2 had begun to lead the way to the modern theory by stating that the extremely strong electrostatic...
Chapter Two
1. Characteristics of amphoteric substances. When an acid is dissolved in water, it splits off hydrogen ions. This change may be attributed to the ability of acids to bind hydroxyl ions. Conversely we may say that bases liberate hy-droxyl ions or bind hydrogen ions. Many compounds possess both acidic and basic properties, although sometimes one or the other property predominates. Such substances which behave both as acids and bases by combining with hydroxyl ions as well as hydrogen ions are...
nchnrr
II. Anilinoazobenzene C6H6N NC6H4NRiR2 unsuitable because of its small solubility . III. Anilinoazoparatoluene CH3C6H4N NC6H4NRiR2 unsuitable because of insolubility . acid V. a-Naphthylaminoazobenzene CeHsN NCi0H6NRiR2 unsuitable because of insolubility . unsuitable because of insolubility . The transformation intervals of the compounds derived by varying Ri and R2 in the above six types of azo indicators are listed in the following table. 1 S. P. L. Sorensen Compt. rend. trav. lab. Carlsberg,...