Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Tanning procedures

The fundamental process of tanning is accomplished by chromium (III) salts ( 80% of all leather produced). Short-chain aliphatic acids - lactic acid among others are sometimes used for masking Cr-tanning agents, but this dominating tanning procedure needs not much RR-based products. [Pg.165]

Many procedures have been studied for detoxification of aflatoxkis, including heat and treatment with ammonia, methylamine, or sodium hydroxide coupled with extraction from an acetone—hexane—water solvent system. Because ki detoxification it is important to free the toxki from cellular constituents to which it is bound, a stabifi2ation of protekis uskig a tanning compound such as acetaldehyde (qv) or glutaraldehyde may be a solution to the problem (98). [Pg.480]

In temperate climates extracts from some plants were found to be excellent preservatives for hides and skins. The hides, with or without hair, were placed in pits in the ground, then covered with alternating layers of bark or leaves and skins. Water was added and later, ie, days or months depending on the thickness of the hide, the hides could be removed, washed, and oiled. The resulting leather is flexible and lasts essentially forever. This procedure was used well into the seventeenth century as the most common method of tanning. In some isolated primitive societies, the method is used in the 1990s. [Pg.80]

The usual procedure in the manufacture of chrome-tanned leathers is the use of a continuous bate, pickle, and tan method. The hides or skins remain in the dmm from the lime washing through the chrome tanning stages. The entire process usually takes about 22—24 hours. The bate, pickle, and tan can be done faster, but most tanners find that a one-day cycle fits well into production scheduling and results in a quaUty leather. [Pg.84]

B. a-Ketoglularic acid. The ester obtained by the foregoing procedure is mixed with 600 ml. of concentrated hydrochloric acid and left overnight. The mixture is concentrated by distillation (Note 5) until the temperature of the liquid reaches 140°. It is poured into an evaporating dish and allowed to cool. The solid mass, weighing 11(3-112 g., is then pulverized. The yield of a-ketoglutaric acid is 92-93% of the theoretical for the last step, or 75-77% based upon diethyl succinate. The light tan product, obtained as described above, is suitable for most purposes, but a purer add, m.p. 109-110° (corr.) may be obtained by recrystallization from an acetone-benzene mixture. [Pg.43]

S. N. Shah, P. C. Harris, and H. C. Tan. Rheological characterization of borate crosslinked fracturing fluids employing a simulated field procedure. In Proceedings Volume. SPE Prod Technol Symp (Hobbs, NM, 11/7-11/8), 1988. [Pg.458]

For the solution of Equation 10.25 the inverse of matrix A is computed by iterative techniques as opposed to direct methods often employed for matrices of low order. Since matrix A is normally very large, its inverse is more economically found by an iterative method. Many iterative methods have been published such as successive over-relaxation (SOR) and its variants, the strongly implicit procedure (SIP) and its variants, Orthomin and its variants (Stone, 1968), nested factorization (Appleyard and Chesire, 1983) and iterative D4 with minimization (Tan and Let-keman. 1982) to name a few. [Pg.176]

The solution of Equation 10.28 is obtained in one step by performing a simple matrix multiplication since the inverse of the matrix on the left hand side of Equation 10.28 is already available from the integration of the state equations. Equation 10.28 is solved for r=l,...,p and thus the whole sensitivity matrix G(tr,) is obtained as [gi(tHt), g2(t,+1),- - , gP(t,+i)]. The computational savings that are realized by the above procedure are substantial, especially when the number of unknown parameters is large (Tan and Kalogerakis, 1991). With this modification the computational requirements of the Gauss-Newton method for PDE models become reasonable and hence, the estimation method becomes implementable. [Pg.176]

Tan, T.B. and N. Kalogerakis, "Improved Reservoir Characterization Using Automatic History Matching Procedures", J. Can Petr. Technology, 32(6), 26-33 (1993). [Pg.401]

Shah, S.N. Harris, P.C. Tan, H.C. "Rheological Characterization of Borate Crosslinked Fracturing Fluids Employing A Simulated Field Procedure" SPE Paper 18589, 1988 SPE Production Technology Symposium, Hobbs, N.M. [Pg.102]

Caution This procedure should be conducted in a good hood. The slurry is stirred while being heated on a steam bath, and solid sodium hydrosulfite is added until the red color of the nitroso compound is completely bleached (Note 5). Then an additional 30 g. of sodium hydrosulfite is added the light tan suspension is stirred with heating for 15 minutes more and is then allowed to cool. The dense diaminouracil bisulfite is filtered from the cooled solution, washed well with water, and partially dried. [Pg.9]

Tan [71] devised a rapid simple sample preparation technique for analysing polyaromatic hydrocarbons in sediments. Polyaromatic hydrocarbons are removed from the sediment by ultrasonic extraction and isolated by solvent partition and silica gel column chromatography. The sulphur removal step is combined into the ultrasonic extraction procedure. Identification of polyaromatic hydrocarbon is carried by gas chromatography alone and in conjunction with mass spectrometry. Quantitative determination is achieved by addition of known amounts of standard compounds using flame ionization and multiple ion detectors. [Pg.135]

Sodium sulfonate 1 has previously been prepared from NaHS03 and vinyltrimethylsilane using sodium nitrite/sodium nitrate as the radical initiator.3 In the submitters hands this protocol resulted in salt 1 as a pale tan powder in only 15-53% yield if 50% (v/v) aqueous methanol is employed as solvent. The yield of 1 could be increased to 63% if 22% (v/v) aqueous methanol is employed. An advantage of this method is the elimination of a potentially explosive perester as radical initiator. However, lower yields of 1 and the subsequent lower yield of the sulfonyl chloride 2 (53% for the sulfonylation, 35% overall from vinyltrimethylsilane) make this procedure less desirable than the method presented. The use of tert-butyl perbenzoate as the radical initiator4 not only provides 1 in a higher yield, but the subsequent conversion to 2 also proceeds in better yield. [Pg.84]

Liu Z-Q, Tan Z-R, Wang D, Huang S-L, Wang L-S, et al. 2002. Simultaneous determination of fluoxetine and its metabolite p-trifluoromethylphenol in human liver microsomes using a gas chromatographic-electron-capture detection procedure. J Chromatogr B 769 305. [Pg.15]

The present procedure makes possible the preparation of large quantities of very pure 3-phenylsydnone without recrystallization. The earlier procedure produced a tan or brown product which lost its color only after several recrystallizations. Slight variations in this procedure can be used to prepare a variety of 3-substituted and 3,4-disubstituted sydnones. [Pg.50]

Crude pentaerythrityl tetrabromide, purchased from Columbia Organic Chemicals Company, Inc., was reerystallized from chloroform to separate the tetrabromide as tan needles, m.p. 158-160°. Alternatively, this material may be obtained by the procedure described in a previous volume of this series. ... [Pg.95]

A colorimetric assay procedure for the quantitative analysis of procaine hydrochloride was developed by Tan and Shelton [38]. The method is based on the interaction of procaine with /i-dimethylamino-... [Pg.430]

In order to estimate kinetic constants for elementary processes in template polymerization two general approaches can be applied. The first is based on the generalized kinetic model for radical-initiated template polymerizations published by Tan and Alberda van Ekenstein. The second is based on the direct measurement of the polymerization rate in a non-stationary state by rotating sector procedure or by post-effect in photopolymerization. The first approach involves partial absorption of the monomer on the template. Polymerization proceeds according to zip mechanism (with propagation rate constant kp i) in the sequences filled with the monomer, and according to pick up mechanism (with rate constant kp n) at the sites in which monomer is outside the template and can be connected by the macroradical placed onto template. This mechanism can be illustrated by the following scheme ... [Pg.96]

One of the checkers added both the dibromoethane and subsequently the ether solution of bis(trifluoro-methyl)bromobenzene via syringe through a rubber septum stopper in place of the addition funnel. Filtration of the benzene solution removes unreacted starting material and other soluble impurities. +The tan solid obtained after drying by the benzene azeotrope procedure is much less soluble in CH2CI2 than the oily solid present before. [Pg.7]

Dichloro-5-nitropyrimidine [4316-93-2] M 194.0, m 100-103", 101-102". If too impure then dissolve in Et2O, wash with H2O, dry over MgSO4, evaporate to dryness and recrystallise from pet ether (b 85-105°) as a light tan solid. It is sol in ca 8 parts of MeOH [Boon et al, JCS 96 1951 Montgomery et al. in Synthetic Procedures in Nucleic Acid Chemistry (Zorbach and Tipson eds) Wiley Sons, NY, p76 1968],... [Pg.177]

In the tanning process hides are first washed or soaked, hair and keratinous debris are removed, bated (enzymes are used to break down non-collagenous components, which are washed out) and the hide is acid-pickled to prepare for the addition of the chromium salt. Contemporary processes are exclusively based on one-bath procedures and utilize chromium(III). The older two-bath process is now obsolete, mainly because it involved the in situ reduction of chromate, a major environmental and toxicological hazard (cf. chromate toxicity p. 947) to chromium(III) on the hide. A useful review of the history of chromium tannage processes is available.1205... [Pg.907]


See other pages where Tanning procedures is mentioned: [Pg.95]    [Pg.95]    [Pg.350]    [Pg.11]    [Pg.407]    [Pg.24]    [Pg.281]    [Pg.284]    [Pg.139]    [Pg.139]    [Pg.142]    [Pg.143]    [Pg.439]    [Pg.147]    [Pg.174]    [Pg.28]    [Pg.100]    [Pg.49]    [Pg.171]    [Pg.2]    [Pg.142]    [Pg.66]    [Pg.649]    [Pg.160]    [Pg.432]    [Pg.7]    [Pg.166]   
See also in sourсe #XX -- [ Pg.95 ]




SEARCH



Tanned

Tanning

© 2024 chempedia.info