Tanning of leather

N Nitrosodimethylamine (formed dunng tanning of leather also found in beer and herbicides)... 

Miscellaneous. In ore flotation, sodium sulfite functions as a selective depressant. In textile processing, sodium sulfite is used as a bleach for wood (qv) and polyamide fibers and as an antichlor after the use of chlorine bleach. Synthetic appHcations of sodium sulfite include production of sodium thiosulfite by addition of sulfur and the introduction of sulfonate groups into dyestuffs and other organic products. Sodium sulfite is useful as a scavenger for formaldehyde in aminoplast—wood compositions, and as a buffer in chrome tanning of leather. 

Potassium dichromate, K2Cr207, is used in the tanning of leather. A 125 mL of solution is labeled 0.145 M K2Cr207. 

Milk of Magnesia is an alkaline (basic) water suspension and creamy-like suspended form of magnesium hydroxide, MglOH). It is used as an antacid to neutralize excess stomach acid. Magnesium can also be used in the form of Epsom salts as a treatment for rashes and as a laxative. A more important commercial use of Epsom salts is in the tanning of leather, as well as in the dyeing of fabrics. 

Stability constant determinations are few 1170 they are summarized in Table 100. Complexa-tion by acidic amino acids is obviously of relevance to the tanning of leather the stability constants for L-glutamic and aspartic acid1171 complexes are much greater than those for glycine or L-alanine.1172,1173,1174 This is probably because the acidic amino acids form tridentate complexes. In contrast, cysteine1173 appears to form glycine-like complexes in moderately acidic solution however, in the solid state L-cysteine is known to be tridentate vide infra). 

The chromates and dichromates are used in making pigments, in dying textiles, and in the tanning of leather. Chromium in the +6 oxidation state is believed to be a carcinogen so chromates and dichromates should be handled carefully. 

The long established use of chromium salts in the tanning of leather has been reflected in interest in the determination of chromium in leather extracts. Generally the leather is leached with acids or complexing agents such as oxine to remove the metal salts. Della Monica and McDowell [189] recommended leather strips be air dried at 80°C for 24 h and ground to pass a 10 mesh screen. The powder was vacuum dried at 70°C for 16 h and then 100 mg refluxed with 25 ml 2M hydrochloric acid. The filtered acid was aspirated into a flame. For chromium a fuel-rich air/acetylene flame or a nitrous oxide/acetylene flame is to be recommended. 

Phenolic compounds typically possess anti-diarrheal and anti-motility properties germicidal activity , herbicidal effect and antiseptic properties". They have also been used in the tanning of leather , as dyes , as a thermal insulating material, as food aroma and liquid smoke". In some cases, the smoke flavour has been attributed to the presence of phenols and sometimes to a single component. The phenols forming the "liquid smoke" which is used to smoke foods are well studied but their role and extent of flavouring have been clarified recently . ... 

Ammonium nitrate and ammonium sulfate both have other uses also. For example, ammonium nitrate is used to make explosives, fireworks, insecticides and herbicides (chemicals that kill insects and weeds), and rocket fuel. Ammonium sulfate is also used in water treatment systems, as a food additive, in the tanning of leather, in fireproofing materials, and as a food additive. 

Higher molecular weight sodium polyphosphates are utilized in the manufacture of processed cheeses, condensed milk and frankfurters and as pigment suspension stabilizers and in the tanning of leather. 

Basic chromium sulfate utilized for the tanning of leather. 

Glyceraldehyde is used in nutrition in the preparation of polyesters and adhesives as a cellulose modifier and in the tanning of leather. It is also used in biochemical research the two isomers are used as reference chemicals because each is one of the... 

Use Source of wattle bark extract, used in vegetable tanning of leather, especially retannage of upper leathers and production of heavy leathers. 

The tannins of some woods, acacias, chestnuts and oaks - and also their barks -were once of importance for the tanning of leather. Yet they have adverse influence on gluing (inhibiting polymerization of adhesives) and in pulping. Today, in the state of Rio Grande do Sul, Brazil, 100,000 ha of Acacia mearnsii provide short fibre for chip export while the 27-28% tannin in its bark supports another industry. 

PCMC has completely replaced pentachlorophenol in the leather industry, particularly as an antimold agent, during chrome tanning of leather. In fact, pentachlorophenol has... 

In connection with the chrome tanning of leather it has been found in technical practice that by the addition of neutral salts it is possible to use more basic chrome liquors The added salt prevents the precipitation of hydrated chromium oxide This phenomen has been regarded as due to an actual increase in hydrogen ion concentration It is much more probable, however, that we are dealing with an increase of activity rather than an increase of mere concentration Instead of dealing with the complex system presented in the tanning bath we shall refer briefly to the results obtained by Thomas and Miss Baldwin loc at) in the chemically better defined case of a solution of chromium chloride... 

Today formaldehyde finds widespread use in the hardening of gelatin, preservation of food, disinfection, tanning of leather and, most important, in the production of resins by condensation with phenol (bakelite) and in the synthetic organic chemical industry. 

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