Deterioration, crystal treatment

Cupferon ammonium salt (7V-nitroso-7V-phenylhydroxylamine ammonium salt) [135-20-6] M 155.2, m 150-155°(dec), 162.5-163.5°, 163-164°, pK 4.16 (free base). Recrystd twice from EtOH after treatment with Norite and finally once with EtOH. The crystals are washed with diethyl ether and air dried then stored in the dark over solid ammonium carbonate. A standard soln (ca 0.05M prepared in air-free H2O) is prepared daily from this material for analytical work and is essentially 100% pure. [Anal Chem 26 1747 1954.] It can also be washed with Et20, dried and stored as stated. In a sealed, dark container it can be stored for at least 12 months without deterioration. Xmax 260nm (CHCI3). [Org Synth Coll Vol I 77 1948 J Am Chem Soc 78 4206 7956.] Possible CARCINOGEN. 

Zeolite samples that were exhaustively treated were gray in color (materials A). Portions of each treated catalyst (0.3 gram) were calcined at 500°C in oxygen for 6 hours, giving a white product (material B). X-ray analysis showed no deterioration in crystal structure on treatment with TMS and subsequent calcination. Surface area measurements using N2 adsorption at — 196°C and the Point B method are also given in Table I. The value for HY zeolite, activated as described, prior to TMS treatment was 840 m2/gram. 

For a zeolite T (OFF stmcture, 0.68 nm XRD pore diameter), Tanaka et al. [131], observed that the separation factor of a water/acetic acid (50/50 wt%) measured at 75°C decreased monotonically after the immersion of the membrane into the acetic acid mixmre. Initially, the separation factor and water flux were 182 and 1.46 kg/m h, respectively, and after 32 h these values changed to 86 and 1.77 kg/m h, showing a deterioration of the membrane. Cui et al. [130] also smdied the stability of crystals and membranes of zeolite T in acid medium. The powders were immersed in a 50/50 wt% water/acetic acid mixture for 7 days at 75°C and also in HCl solutions 0.5 and 1 M for 1 h at 50°C. The analysis of the samples after the treatment by ICP and XRD indicated that the sample treated in the acetic acid solution maintained its original Si/Al ratio equal to 4 however, the hydrochloridric acid treatment with the 1 M solution destroyed the zeolite stmcmre and the 0.5 M solution dealuminated the zeolite to a Si/Al equal to 8.9 and the XRD analysis corresponded to zeolite T. The membrane performance, after being used for 1 week at different water/acetic acid concentrations, remains almost unchanged and the separation factor of the membrane treated in HCl dramatically decreased as was expected. 

In order to improve the resolution efficiency, i. e. to increase the yield of the less-soluble three-component diastereomeric salt without any deterioration in the diastereomeric purity, the effect of water in ethanol was examined for a range of 2-75% (w/w) water contents. Table 5.10 shows that the enantiomeric excess of the amine recovered from the less-soluble diastereomeric salt increased and then decreased with decreasing water content, until finally no crystal was obtained. This result indicates that the presence of water in a solvent is essential for the formation of the less-soluble diastereomeric salt and that the three-component salt could possibly deposit in a larger quantity from a solvent less polar than ethanol. On the basis of this consideration, less polar alcohols were used as solvents in the presence of a small amount of water (Table 5.11). When 2-butanol containing two moles of water was used as a solvent, the highest resolution efficiency was achieved. The diastereomeric salt crystals, obtained in all the systems shown in Table 5.11, contained an equimolar amount of water as a component. These results obviously show that water plays a very important role in the formation of stable diastereomeric salt crystals with satisfactory diastereomeric purity. The recrystaUization of the crude salt once from aqueous 2-butanol gave the diastereomeric three-component salt with diastereomeric purity of more than 95 %. The final product (S)-3-(methylamino)-l-(2-thienyl)propan-l-ol with more than 99.5% ee was obtained upon treatment of the recrystaUized salt with aqueous sodium hydroxide, followed by extraction with 2-butanol and crystallization from toluene [21]. 

Heterogeneous catalysis has to deal not only with the catalyzed reaction itself but, in addition, with the complexities of surface properties (different crystal surfaces, different catalytic sites), possible segregation of adsorbates (so-called island formation), contamination or deterioration of catalytic sites, and adsorption and desorption equilibria and rates. Moreover, mass transfer to and from the reaction site is a factor more often than in homogeneous catalysis. In practice, these complications may affect behavior more profoundly than does the kinetics of the surface reaction itself. A practical and balanced kinetic treatment therefore uses simplifications and approximations much more generously than was done in the preceding chapters. Excellent textbooks on the subject are available [G1-G7], so coverage here can remain restricted to a critical overview and indications showing when and how concepts and methods developed in the earlier chapters can be useful. 

Renal functional deterioration usually occurs within the first few days of therapy, and may be detected after only a few doses or, more rarely, later in the course of treatment [5-15]. Patients may be asymptomatic, but nausea, vomiting, and abdominal, back, or flank pain are common. Oliguria is uncommon. The rise in the serum creatinine concentration is usually modest, and dialysis has only rarely been necessary. Most patients recover renal function within 3 to 14 days of stopping acyclovir therapy, reducing the dose, or increasing hydration [5, 6, 8-15]. Urinalysis usually shows mild proteinuria, microscopic hematuria, and variable degrees of pyuria. Birefringent needle-shaped crystals may be seen either free or within white blood cells in the urine sediment [10]. It should be noted, however, that acy-... 

Ni (0) catalyst can be produced with the aid of plasma. The activation energy of hydrogen production from sodium borohydride with this catalyst system was calculated as 51.35 kj moT With this approach the mass specific surface area can be increased from 0.0063 m g to 23.11 m g without the crystal structure deteriorating. The reason is thought to be the higher resistivity of plasma treated Ni to aggregations. Plasma treatment can enhance... 

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