bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of the Third Virial Coefficient on the Intensity of Light Scattered by Mixed Aqueous Solution of Poly(vinylpyrrolidone) and Sodium Dodecyl Sulfate
Authors: Nakagaki Masayuki , Shimabayashi Saburo 
Published: July 2006

Abstract
It was found that the reduced intensity of scattered light, Rθ, increases and then decreases with polymer concentration, becoming maximum for a certain concentration of the polymer, when the third virial coefficient, A3, is positive. The theoretical concentration of polymer for the maximum Rθ is (3A3M2)−1⁄2, where M2 is the molecular weight of the polymer. This was observed in the case of the aqueous solution of poly(vinylpyrrolidone) (PVP) mixed with sodium dodecyl sulfate (SDS). In the mixed solution, PVP and SDS form a complex which behaves like a polyelectrolyte with or without a simple salt of low concentration. Such a solution often has higher-order virials. The value of the polymer concentration for the maximum scattered light intensity agreed with the theoretical value.
Intramolecular Catalytic Substitution Reaction of N-(ω)-Bromoalkyl)pyridinium Bromide with Potassium Cyanide
Authors: Yamada Masahide , Sakakibara Tohru , Takamoto Tetsuyoshi , Sudoh Rokuro 
Published: July 2006

Abstract
It was found by means of NMR spectrometric and potentiometric titration technique that the intramolecular catalytic substitution of N-(ω-bromoalkyl)pyridinium bromide with KCN proceeds in the range n=2–6 of methylene chain on the pyridinium salt and the intermolecular substitution in n=7 and 9, and the addition of cyanide anion to the pyridine ring takes place only for n=1.
Active Sites of MoO3 and MoO3–SiO2 Catalysts for Isomerizaiton of Butenes. Characterization by Tracer Study
Authors: Hattori Hideshi , Maruyama Kazumasa , Tanabe Kozo 
Published: July 2006

Abstract
Deuterium atom distribution of butenes in the coisomerization of cis-2-butene d0/d8 over MoO3 and MoO3–SiO2 indicates that the reaction involves intermolecular hydrogen transfer for both catalysts. Butenvs produced over deuterium-exchanged MoO3–SiO2 contain deuterium atoms, those produced over deuterium-exchanged MoO3 none.
Radical Reaction in a Silent Electric Discharge of Ethylene
Authors: Itoh Junichi , Takimoto Kazuto , Tsuda Satoru 
Published: July 2006

Abstract
In the silent electric discharge of ethylene, it was revealed, by studying the effects of various scavengers on the formation of gaseous products, that the radical reaction plays an important role, unlike as in the reaction in radiolysis. Furthermore, the existence of several intermediates was directly or indirectly demonstrated by using an ESR technique and by adding iodine as a radical scavenger.
Ligand-Substitution Reaction of Bis(acetylacetonato)copper(II) and Bis(acetylacetonato)zinc(II) with 2-(2-Pyridyl)benzimidazole
Authors: Kondo Michio 
Published: July 2006

Abstract
The reaction of bis(acetylacetonato)copper(II) with 2-(2-pyridyl)benzimidazole (1) in ethanol was studied by means of absorption, fluorescence, and 1H NMR spectroscopies, and it was found that one of the acetylacetonate anions in the complex is replaced by the anion of 1. Bis(acetylacetonato)zinc(II) reacts with 1 in a similar manner. Neither acetylacetonate reacts with 2-(3-pyridyl)- or 2-(4-pyridyl)benzimidazole.
Vilsmeier Reaction of Phenols. I. Synthesis of Aryl Formates
Authors: Morimura Syoji , Horiuchi Hideo , Murayama Keisuke 
Published: July 2006

Abstract
The reaction of phenol and o-t-butylphenols with N,N-dimethylformamide–phosphoryl chloride complex in dimethylformamide afforded the corresponding formates in fairly good yields. The scope and limitation of o-formylation of highly sterically hindered phenols with the complex were also examined.
A New Synthesis of 4-Methoxy-6-valeryl-5,6-dihydro-2-pyrone
Authors: Takeda Akira , Amano Eiichiro , Tsuboi Sadao 
Published: July 2006

Abstract
The reaction of ethyl 2-acetoxy-3-oxoheptanoate with γ-bromo-β-methoxy-cis-crotonate in the presence of sodium ethoxide afforded diethyl 3-methoxy-5-hydroxy-5-valeryl-2-hexenedioate (7) in 65% yield. Treatment of 7 with a dilute aqueous NaOH in acetone gave (±)-4-methoxy-6-valeryl-5,6-dihydro-2-pyrone, a key intermediate leading to pestalotin, in 41% yield.
Mono S-Acylated 1,8-Naphthalenedithiol. Isolation and Characterization of Tetrahedral Intermediate in the Intramolecular Acyl Transfer Reaction
Authors: Takagi Makoto , Ishihara Ryoji , Matsuda Tsutomu 
Published: July 2006

Abstract
The tetrahedral intermediate in the intramolecular acyl transfer reaction of mono-S-acylated 1,8-naphthalenedithiol was found to be sufficiently stable to allow isolation or direct characterization by spectroscopy. Formation of carbenium ion from the intermediate is suggested in sulfuric acid.
Utilizing Emulsification in the Synthesis of Dihydro-exo-dicyclopehtadienyl Ethers and Their Esters
Authors: Hatano Akira , Iwase Yoshiyuki 
Published: July 2006

Abstract
Alcohols and carboxylic acids were subjected to an addition reaction with dicyclopentadiene, using dodecylbenzenesulfonic acid both as the emulsifying agent and the acid catalyst. Dihydro-exo-dicyclopentadienyl ethers and their esters were syntheized in good yields and found to be free of undesirable side reactions.
Isolated Molecule Approach to the Orbital Study of Chemical Reactions. I. Bimolecular Nucleophilic Substitution
Authors: Fujimoto Hiroshi , Kosugi Nobuhiro 
Published: July 2006

Abstract
A method of analyzing chemical interactions between two systems is presented and applied to the bimolecular nucleophilic substitution of methylfluoride by fluoride ion. In order to get a clear insight into the mechanisms of chemical interactions, the interacting system has been represented by a combination of various electron configurations of the reactants involved. The matrix elements necessary for the configuration interaction have been obtained by transforming the MO’s of the isolated reactants into a set of orthogonalized functions. The change in the energy and the redistribution of the electrons due to the interaction in the reaction have been calculated by the use of the ab initio (STO-3G) MO’s and have been divided into the Coulomb, exchange, delocalization, and polarization interactions. A comparison of the results with the results of the SCF CI calculations of the composite system has shown the utility of the method in studying weak and moderately strong interactions between two systems.
Switching in Copper-Phthalocyanine Films
Authors: Sadaoka Yoshihiko , Sakai Yoshiro 
Published: July 2006

Abstract
Bistable switching between two impedance states was observed in copper-phthalocyanine films. The turn-on can be interpreted in terms of the steady thermal breakdown model. The stable high conductivity in the on-state is attributed to the partly carbonized copper-phthalocyanine which was formed by Joule heating along the filamentary paths. The J-V characteristic in the off-state and the threshold-field strength were found to be expressed as J∝V6|d3.8 and Eth∝1|d0.46 respectively.
The Dimorphism and Electronic and Vibrational Spectra of 2-Anilino-1,4-naphthoquinones
Authors: Matsunaga Yoshio , Miyajima Nobuhiko , Togashi Atushi 
Published: July 2006

Abstract
Dimorphic forms were isolated for over ten derivatives of 2-anilino-1,4-naphthoquinone, 2-anilino-3-chloro-1,4-naphthoquinone, and 2-anilino-3-bromo-1,4-naphthoquinone carrying substituents on the phenyl ring. One of the two forms exhibits a relatively sharp vibrational band near 3300 cm−1, the other, a relatively broad band at a lower wave number. The spectra in the region from 700 to 1700 cm−1 are often markedly different from each other. In several instances, the two forms are differently colored. This difference is attributed to the appearance of, or a change in the intensity of, an intermolecular charge-transfer absorption band. Not only the dimorphic forms, but also most of the derivatives examined, could be classified into two groups on the basis of the location and the sharpness of the vibrational band appearing in the region from 3150 to 3350 cm−1.
Shock Tube Study of the H–D Exchange Reaction between Acetylene and Deuterium
Authors: Ogura Hiroo 
Published: July 2006

Abstract
H–D exchange reaction between acetylene and deuterium has been investigated in a single-pulse shock tube in the temperature range 1200–1500 K. Empirically, in the C2HD appearance the order with respect to acetylene was 0.25±0.09, and that with respect to deuterium 1.14±0.15. The rate constant of 1.39 th order for the C2HD increase was obtained as; k(cm1.17 mol−0.39 s−1)=(24.4±7.5)×1011exp((−51200±2400)⁄RT). The isotopic distributions of acetylene and hydrogen as determined by mass spectrometry suggest that C2D2 and H2 are formed by the subsequent reactions of C2HD and HD, respectively. A free-radical chain mechanism initiated by the same bimolecular reaction of acetylene, viz. 2C2H2→C4H3+H, as in the pyrolysis and hydrogenation of acetylene was proposed. A steady-state treatment of the proposed mechanism shows that the empirical rate and concentration dependence of the C2HD increase are in line with those of the steady-state rate.
The Transition to Detonation from Deflagration in Ethylene–Oxygen Systems
Authors: Inomata Tadaaki , Suzuki Momotaro 
Published: July 2006

Abstract
The flames of ethylene and oxygen mixtures (initial pressure, 50–500 mmHg, and ethylene content, 20–40%) were studied, especially for the transition to detonation from deflagration. The flames may roughly be divided into four groups: A, a flame without any shock wave generation; B, a flame with a shock wave generation; C, a flame with many shock waves and much turbulence of the flame, and finally D, the detonation produced by the collision of a flame and a reflected shock wave at the bottom of the tube. The flame transit to detonation from deflagration is a linear relation between the velocities of the flames at the point of detonation and DID, or the distance from the point of ignition to the detonation for all the sorts of flames given above, in spite of several apparent differences.
The Molecular Structure of μ-Carbonyl-di-μ-diphenylmethylene-bis(π-cyclopentadienylrhodium), [(π-C5H5)2Rh2{C(C6H5)2}2(CO)]
Authors: Ueda Hiroshi , Kai Yasushi , Yasuoka Noritake , Kasai Nobutami 
Published: July 2006

Abstract
The molecular structure of [(π-C5H5)2Rh2{C(C6H5)2}2(CO)] has been determined from three-dimensional X-ray diffraction data (R=0.040 for 2394 reflections). The crystal belongs to the monoclinic system, space group A2/a, with four formula units in a cell of dimensions: a=19.967(5), b=10.343(1), c=16.526(4) Å, and β=123.05(2)°. The molecule has C2 symmetry: the two-fold axis passes through the bridge carbonyl group, being perpendicular to the Rh–Rh bond (Rh–Rh=2.548(1) Å). The diphenylcarbene moieties bridge between rhodium atoms. The planar cyclopentadienyl rings lie 1.94 Å from the nearest rhodium atom and exihibit the usual π-bonded geometry.
The Synthesis of Dimethyl dl-3-Ethyl-4-methyl-1,2-cyclopentanedicarboxylates
Authors: Ito Shosuke , Hirata Yoshimasa 
Published: July 2006

Abstract
The four 3,4-cis-stereoisomers of dimethyl dl-3-ethyl-4-methyl-1,2-cyclopentanedicarboxylates (1a, 1b, 1c, and 1d) have been synthesized and their configurations established. A comparison of the spectral data and the GLC behaviors has shown that the corresponding ester, one of the key degradation products of ikarugamycin, has the r-1, t-2, c-3, c-4-configuration (1a). The r-1, t-2, c-3, t-4-stereoisomer (1f) has also been prepared.
The Isotope Effect on the Quenching of the Cadmium Triplet State by Methanol
Authors: Tsunashima Shigeru , Morita Kuniko , Sato Shin 
Published: July 2006

Abstract
The isotope effect on the Cd-photosensitized emission of methanol has been investigated using CH3OH, CH3OD, CD3OH, and CD3OD. The relative quenching efficiencies for the 326.1 nm resonance line were 1 : 0.3 : 0 .9 : 0.3 in the order of CH3OH, CH3OD, CD3OH, and CD3OD. The emission intensities from the intermediate complex between an excited cadmium and methanol were also measured. The band-shape was not affected by the substitution of D atoms. The intensity ratio was 1 : 3.1 : 1.1 : 3.1 in the order of CH3OH, CH3OD, CD3OH, and CD3OD, when the incomplete quenching was corrected. These results were explained by the following quenching processes:
Cd^*+CH_3OH & →Cd···H···OCH_3
&→Cd···O&lt;_CH_3^H
where Cd* represents Cd(3P1) and/or Cd(3P0). The D/H kinetic isotope effect on the former process was estimated to be 0.3
A Temperature-Jump Study of the Formation Reactions of Nickel(II)–Pyridine Complexes in Aqueous Solutions
Authors: Tamura Kiyoshi , Harada Shoji , Yasunaga Tatsuya 
Published: July 2006

Abstract
A temperature-jump study reveals two relaxation phenomena in aqueous nickel (II)–pyridine solutions. One is observed in a metal-rich and low-concentration system, while the other is found only in a ligand-rich and high-concentration system. The relaxation processes are ascribed to the complex formation reactions:
Ni^2++py\oversetk_1\undersetk_-1\ightleftharpoonsNi(py)^2+ and Ni(py)_2^2++py\oversetk_3\undersetk_-3\ightleftharpoonsNi(py)_3^2+
The rate constants reported are: 3.6×103 M−1 s−1 for k1 and k3, 37 s−1 for k−1 and 760 s−1 for k−3, at 25 °C. The effect of the coordinated pyridine molecules on the reactivity of the metal is discussed.
The Effect of a Solvent on the Carbonylation of Methanol Catalyzed by Rhodium Complexes in the Presence of Methyl Iodide
Authors: Matsumoto Toshio , Mori Kunio , Mizoroki Tsutomu , Ozaki Atsumu 
Published: July 2006

Abstract
In the synthesis of acetic acid by the carbonylation of methanol catalyzed by RhCl3·3H2O or Rh2Cl2(CO)4in the presence of methyl iodide, it was found that ketone solvents, such as acetophenone and benzophenone, keep both the catalytic activity and selectivity high, even at an elevated temperature. The kinetic results in acetophenone are in agreement with the mechanism proposed by Paulik and Roth. The effect of the ketone solvent was discussed by taking account of the competitive oxidative addition of hydrogen iodide with methyl iodide.
Studies of Peptide Antibiotics. XXXVI. Synthesis and Biological Activity of [5,5′-Leucine]-gramicidin S
Authors: Abe Okitoshi , Utsumi Yoko , Izumiya Nobuo 
Published: July 2006

Abstract
An analog of gramicidin S, in which 5,5′-proline residues were replaced by leucine, was prepared in order to investigate the effect of the introduction of hydrophobic side groups on the antibacterial activity and on the conformation. Also the solubility problems encountered during the synthesis of this analog are described. No significant effect was observed on the cyclization reaction by the replacement of 5,5′-proline to leucine residues. This analog exhibited comparable biological activity and the similar conformation to the natural gramicidin S. These studies suggested that the imino groups of 5,5′-proline residues have no significant roles on both antibacterial activity and conformation of this antibiotic.
The Photobromination of β-Styrenesulfonamides and Syntheses of 2-Arylacetylene-1-sulfonamides
Authors: Hasegawa Kiyoshi , Hirooka Syuzi , Kawahara Hiroshi , Tanaka Atsushi , Nomura Masahiro , Hori Yutaka 
Published: July 2006

Abstract
The photobromination of trans-β-styrenesulfonamides in acetic acid at 16–18 °C gave about 75 : 25 mixtures of threo (cis adducts)- and erythro-1,2-dibromo-2-arylethane-1-sulfonamides (trans adducts). A similar photobromination of cis-β-styrenesulfonamide afforded a 33 : 67 mixture of the threo (trans adduct)- and the erthro-dibromides (cis adduct). The diastereomers could be separated by fractional recrystallization. The cis adducts were shown to be formed neither by secondary isomerization nor by (presumably) ionic addition. The trans dehydrobromination of the threo- and the erythro-dibromides with Et3N gave (Z)- and (E)-β-bromo-β-styrenesulfonamides respectively, which underwent further facile dehydrobromination with aqueous 1 M NaOH at 45–50 °C to afford 2-arylacetylene-1-sulfonamides. They were also prepared from (Z)-α-chloro-β-styrenesulfonamide by an analogous procedure.
Diphosphine–Rhodium Complex-Catalyzed Hydroformylation of α,β-Unsaturated Esters
Authors: Tanaka Masato , Hayashi Teruyuki , Ogata Ikuei 
Published: July 2006

Abstract
The product distribution in the hydroformylation of α,β-unsaturated esters (ethyl acrylate, methyl methacrylate, methyl crotonate, and methyl tiglate) catalyzed by Rh2Cl2(CO)4 was studied at 150 °C under 100 atm of synthesis gas (CO/H2=1/1) in the absence or presence of various additional phosphorus ligands. In order to attain a high selectivity of α-formylation (&gt;80%), the addition of shorter methylene-chained diphosphines (R2P(CH2)nPR2, R=phenyl or cyclohexyl, n=2–4) to the reaction system was essential, while the use of Rh2Cl2(CO)4 alone or in combination with triphenylphosphine or a longer diphosphine, Ph2P(CH2)5PPh2, resulted in a very low α-selectivity. The effects of the reaction variables on the product distribution were also examined for acrylate and methacrylate using Ph2P(CH2)4PPh2 and Ph2P(CH2)2PPh2, respectively, as additional ligands.
Syntheses of 4′-Deoxykanamycin and 4′-Deoxykanamycin B
Authors: Miyake Toshiaki , Tsuchiya Tsutomu , Umezawa Sumio , Umezawa Hamao 
Published: July 2006

Abstract
4′-Deoxykanamycin (9) was prepared from kanamycin via N-benzyloxycarbonylation, 4″,6″-O-cyclohexylidenation, selective benzoylation at 2′,3′, and 2″-hydroxyl groups, 4′-O-mesylation, 4′-iodination, 4′-hydrogenation, and removal of the protective groups. 4′-Deoxykanamycin B (19) was analogously prepared from kanamycin B. 4′-O-Tosyl derivative of kanamycin B was also led to 19. Selective formylation of the 3′-hydroxyl group of a protected kanamycin B derivative with N,N-dimethylformamide-tosyl chloride followed by mesylation of the unstable 3′-O-formyl derivative also led to 4′-deoxykanamycin B. Throughout the syntheses, the 4′-hydroxyl group of the protected kanamycins was found to be least reactive for benzoylation among the 2′,3′,4′, and 2″-hydroxyl groups. The 13C NMR spectrum of 9 was also measured. It was concluded that 4′-deoxygenation of antibiotics structurally related to kanamycin caused the resonances of 13C-6′ downfield shift.
The Reaction of Nucleophilic Reagents at the β-Position of 3-Bromo-4-nitropyridine N-Oxides
Authors: Matsumura Eizo , Ariga Masahiro 
Published: July 2006

Abstract
The reactions of 3-bromo-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (1a:R1=H, R2=Me, X=H; 1b:R1=R2=Me, X=H; 1c: R1=R2=H, X=Br) with diethyl sodiomalonate, ethyl sodiocyanoacetate, and ethyl sodioacetoacetate have been carried out. The treatment of 1a, 1b, and 1c with diethyl sodiomalonate gives 3-[bis(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-5-X-pyridine N-oxides (2a, 2b, and 2c) and 4-[bis(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxides (3c). With ethyl sodiocyanoacetate, 3-[cyano(ethoxycarbonyl)methyl]-4-nitro-2-R1-6-R2-pyridine N-oxides (4a and 4b) and 4-[cyano(ethoxycarbonyl)methyl]-3,5-dibromopyridine N-oxide (5c) are obtained. With ethyl sodioacetoacetate, 1a and 1c give 3-[acetyl(ethoxycarbonyl)methyl]-6-methyl-4-nitropyridine N-oxide (6a) and/or 3-ethoxycarbonyl-2-methyl-6-R1-7-X-furo[3,2-c]pyridine N-oxides (7a and 7c), but 1b is unaffected by ethyl sodioacetoacetate under the given conditions. The electronic and steric effects of methyl and bromo groups for the reactions are discussed.
Synthesis of Streptolidine Lactam, a Guanidine-contain ing Amino-acid Lactam Moiety of Streptothricin Antibiotic Group
Authors: Kinoshita Mitsuhiro , Suzuki Yoshiharu 
Published: July 2006

Abstract
Streptolidine lactam (3) present in streptothricin antibiotics was stereospecifically synthesized. 3,4-Anhydro-1,2 : 5,6-di-O-isopropylidene-d-iditol (4) was converted into the 3,4-bis(benzyloxycarbonylamino)-3,4-dideoxy-d-mannitol derivative 7 via the 3,4-diazido-3,4-dideoxy-d-mannitol derivative 6. De-O-protection of 7 followed by two-stage oxidation with periodate-bromine afforded 2,3-bis(benzyloxycarbonylamino)-2,3-dideoxy-d-arabono-1,4-lactone (8), which was transformed into the azide lactone 9. Selective hydrogenolysis of 9 with Raney Ni gave the N-protected amino sugar lactam 10. O-Tetrahydropyranylation of 10 followed by hydrogenolysis afforded the O-protected amino sugar lactam 12. Treatment of 12 with cyanogen bromide in water gave the O-tetrahydropyranylated streptolidine lactam 13, which on mild acid hydrolysis afforded 3 (hydrochloride). The amino sugar lactam 14 obtained by hydrogenolysis of 9 with palladium black was also treated with cyanogen bromide to yield 3 (hydrobromide). Acid hydrolysis of 3 gave streptolidine (2) (dihydrochloride) identical with that derived from the antibiotics.
Studies on Separation of Amino Acids and Related Compounds. VIII. Preparative Separation of Isomeric l-Aspartyl-l-phenylalanine Methyl Esters and Related Dipeptide Esters by Ion-Exchange Chromatography
Authors: Yasutake Akira , Aoyagi Haruhiko , Izumiya Nobuo 
Published: July 2006

Abstract
Authentic peptides, α- and ω-isomers of l-aspartyl (or l-glutamyl)-l-phenylalanine (or l-tyrosine) methyl ester, were synthesized by conventional methods. Among these eight peptides, α-l-glutamyl-l-phenylalanine methyl ester showed the tendency to convert to the corresponding dipeptide anhydride even under mild conditions. The experiments on a small column of Dowex 50 cation exchange resin were carried out with a model mixture composed of the α- and ω-isomers, and the optimum conditions for the complete separation of both isomers were determined. A synthetic mixture composed of the α- and ω-isomers was prepared readily through the coupling of benzyloxycarbonyl-l-aspartic acid (or glutamic acid) anhydride with l-phenylalanine (or l-tyrosine) methyl ester and subsequent hydrogenation. The synthetic mixture was separated by the use of a large ion exchange column and each isomer was obtained in a good yield.
Effects of Metal Ions on Reactivity Patterns in the Reactions of 1-Methoxycarbonyl-2-imidazolidinone and Its Derivatives with Butylamine
Authors: Matsumura Noboru , Kawai Hiroshi , Otsuji Yoshio , Imoto Eiji 
Published: July 2006

Abstract
The reactions of 1-methoxycarbonyl-2-imidazolidinone, 3-acetyl-1-methoxycarbonyl-2-imidazolidinone and 1-methoxycarbonyl-cis-perhydrocyclopenta[d]imidazol-2-one with butylamine were studied in the absence and presence of various metal ions. Certain bivalent ions such as Mg2+, Ca2+, and Mn2+ enhanced an electrophilic reactivity of the methoxycarbonyl group and facilitated the transfer reaction of this group to butylamine, especially when the imidazolidinone moiety of substrates bears the methoxycarbonyl group at one N-position and a hydrogen atom at the other N-position. Whereas monovalent ions such as Na+ and Ag+, and bivalent ions such as Zn2+ and Cu2+, had no appreciable effect on the reactivity, and exhibited almost the same reactivity patterns as those observed in the reactions in the absence of metal ions. A possible explanation is given in terms of the stability of coordination complexes which are formed by the interaction between the imidazolidinone moiety of substrates and added ions.
A New Method for Measuring Surface Acidity. The Titration of Silica–Alumina with the Indicator Itself
Authors: Take Jun-ichiro , Kawai Haruyuki , Yoneda Yukio 
Published: July 2006

Abstract
A new method has been proposed for measuring the surface acidity of solid acids. The method involves the titration of a solid acid with the indicator itself in a nonpolar solvent; it determines the number of acid sites from the amount of the indicator chemisorbed at saturation. The titration of silica-aluminas with 4-anilinoazobenzene (pKa=1.5) itself yielded an acid content smaller than the butylamine titration method with the same indicator. This difference in acid content was ascribed to the difference in the base strength of the titrants. Similarly, titration with trans-azobenzene (pKa=−2.9) itself produced an acid content smaller than that with 4-anilinoazobenzene itself.