Aluminium tannings

Oil-tanned chamois leather Alum-tawed skins Formaldehyde-tanned leather Aluminium-tanned skins Vegetable-tanned leather (hydrolysable) Vegetable-tanned leather (condensed) Chrome-tanned leather... 

In addition to their energetic value, oil shales have also been used as sources for other materials, such as alumina, ammonium sulphate, phosphate, sodium carbonate, S, U, V, and Zn (Murray 1974). In the early 17th century, potassium aluminium sulphate was extracted from the Alum Shales in Sweden for use in the tanning and textile industry. It was only by the 19th century that hydrocarbons were being extracted from these Alum Shales while, in the 1960s, their content of U and V was being exploited (Dyni 2000). 

Hydroxy-5,6,7,8-tetrahydro-2-acetonaphthone [3].—On mixing 32 1 g of aluminium chloride with 35 0 g (0 184 mole) of 5,6,7,8-tetrahydro-2-napbthyl acetate [10] a vigorous reaction occurred immediately, and hydrogen chloride was evolved rapidly. After the initial reaction had subsided, the mixture was heated for 0 5 hour at 130°. The tan solid obtained on decomposition of the cooled mixture... 

The ash of true leather tanned with tannin consists essentially of calcium carbonate with traces of iron and of phosphates. Coloured leathers may contain metals from the mordants used (tin, copper, iron, chromium, aluminium) tin may also be introduced as stannous chloride used for bleaching. Small quantities of silicates (talc, kaolin) may be employed in the treatment of the leather. Finally, other mineral matters (barium, magnesium and lead salts and sodium chloride) may have been added as filling to increase the weight. Complete quantitative analysis of the ash is rarely necessary, but determination of its calcium content is sometimes required, this being made by the ordinary methods. 

Ash.—As in tanned leather, but with a smaller quantity of substance. The result obtained does not give the true proportion of mineral matter, since the acids combined with the chromium and aluminium oxides axe eliminated during calcination. 

From among the methods mentioned above, iron has been determined with the use of Chrome Azurol S - in waters [176], Bromopyrogallol Red - in magnetic Fe-Co-Ni films [177], sulphanilic acid - in blood plasma [129] and in plants [109], Tiron - in geological materials [114], in aluminium alloys and copper [115], 2,2 -diquinoxalyl - in niobium oxide [128], PAN - in alloys and biological samples [79] and in waste waters [178], TAN - in geological samples [83], 5-Br-PADAP - in biological samples (by derivative spectrophotometry) [91] and in copper alloys [179], and morin - in copper-chromium and nickel-chromium alloys [122]. 

As a method of avoiding the damage caused by aqueous solutions, an attempt was made to find an aluminium compound which was both soluble in a non-polar solvent and had significant tanning powers. A wide range of compounds was screened and one, an aluminium isopropoxyde derivative chelated with ethyl acetoacetate called, for simplicity, aluminium alkoxide, was found to have the optimum combination of properties. This is used as follows. 

Al alloys are frequently used to prepare composites with p- and y-BN [9 to 12]. This can be done by sintering the reaction mixture originating from preformed p-BN particles or from a-BN powder. The aluminium is often combined with transition metal carbides or nitrides (especially TiC and TiN) in order to form the binding phase [13 to 39]. However, TiC, TiN, and TiBg also form composites with the hard BN phases without the addition of aluminium [40 to 46] addition of TaN has also been reported [47]. 

The tanning proper is carried out by the use of tannin, or vegetable extracts, or by minerals such as the salts of iron, aluminium, and chromium. The function of the tanning agent is to form an insoluble precipitate with the components of the hide. This takes place usually in acid solution. The resulting insoluble substance, leather, is much more inert chemically than the hide, and as it is insoluble in water there is no increase of osmotic pressure and hence no appreciable swelling. 

Chromium salts are more advantageous for tanning than either those of iron or of aluminium, although aluminium salts are preceptibly better than those of iron. The reason given is that the latter are hydro-llzed too greatly, and the salt, therefore, does not so easily penetrate the cell substance. The effect of iron salts can be improved by the aid of protective colloids such as blood, albumin, gelatin. 

Figure 13 The dielectric constant and the effective tan 6 for hot pressed aluminium nitride as a function of the temperature. (After ref 3).

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