As the process of dégras manufacture is obviously mainly one of oxidation, many attempts have been made to produce it by direct oxidation of fish oils, without the agency of skins, both by blowing air through the oil, and by addition of oxidising agents such as nitric acid. Eitner states that such oxidised oils are more liable to “spue” than the original oils, as they already contain large quantities of resinised products; but this is certainly not true of all artificial dégras, some of which answers its purpose perfectly as a currying material, though it is very probably justified in other cases. Of course the methods of successful manufacturers are kept as profound secrets.
Dégras and sod oil, when deprived of water, are dark and viscous oils, of high specific gravity (0·945-0·955), and therefore heavier than the oils which have been employed in their manufacture.
Waxes, as has already been stated, differ in their chemical character from true fats, in that their fatty acids, which are mostly of high molecular weight, are combined, not with glycerine, but with alcohols, also of high molecular weight and of wax-like consistency. Most waxes are solid bodies of high melting point, but some oils, especially sperm and bottlenose oils, are chemically liquid waxes; woolfat contains a considerable proportion of waxes; and many marine oils, such for instance as shark-liver oil ([p. 366]), contain waxes in smaller quantity in mixture with true fatty oils.
Sperm Oil (Fr. Huile de cachalot; Ger. Spermacetioel, Walratoel) is obtained from the sperm whale, an inhabitant of the Antarctic seas. “Arctic sperm” (Ger. Doeglingthran) is a very similar oil obtained from the “Bottlenose whale.” These oils are very fluid, do not dry, and are excellent lubricating oils for light machinery, and also good lamp oils. They contain little if any glycerides, and about 40 per cent. of unsaponifiable solid alcohols, which are soluble in ethyl-alcohol, and must not be confused with ordinary unsaponifiable mineral oils, which are frequently used as adulterants in mixture with fatty oils to adjust gravity and the “saponification value.” Mineral oils are liquid, and insoluble in alcohol. Sperm oil is the lightest of ordinary oils, its gravity being only about 0·880 at 15° C. From its price it is particularly liable to sophistication. It is used in leather manufacture in the finishing of some fine leathers, and sometimes as a constituent of fat-liquors. Spermaceti, a wax also obtained from the sperm whale, is an occasional constituent of leather polishes.
Beeswax (Fr. Cire des abeilles; Ger. Bienenwachs) is one of the most important waxes for the leather-dresser. As is well known, it is obtained from the honeycomb of the ordinary bee. It is a yellowish solid body, fairly plastic when fresh, and of “waxy” feel. At low temperatures it is brittle and of fine granular texture, and when pure is almost tasteless. It is often bleached by repeated melting and exposure to sunlight. As wax always contains a considerable amount of pollen it may be identified when in admixture with other substances by means of the microscope.
Beeswax is almost insoluble in cold alcohol, but boiling alcohol dissolves out the contained cerotic acid, which crystallises from it on cooling. Wax is saponified by alcoholic potash, but the resulting myricyl alcohol (about 54 per cent.) is not capable of further saponification.
Beeswax is frequently adulterated. Water and mineral matters (ochre, gypsum, etc.) also flour, starch, tallow, stearic acid, Japan wax, carnaüba wax, resin and paraffin-wax are among the substances most commonly used in its sophistication.
The detection of these, and especially of the other waxes, is so difficult that it will not be described here. The reader is, however, referred to Benedikt and Lewkowitsch’s ‘Oils, Fats and Waxes,’ for further information.
Carnaüba Wax (Fr. Cire de carnauba; Ger. Cearenwachs, Carnaubawachs) has come largely into use recently owing to the advent of the coloured leather shoe. As it is a very hard wax it has become very popular with boot polish makers, its low price being also in its favour. Carnaüba wax is an exudation from the leaves of Copernica cerifera, a palm indigenous to Brazil, and is, on this account, often known as Brazilian wax. It is difficult to saponify, and with different experimenters has yielded very varied results on analysis; it is generally agreed, however, that it is a complicated mixture of several of the higher alcohols and acids.
Japan Wax is not a true wax, but a fat consisting of glycerides. It is a pale yellow, hard, waxy substance obtained from the berries of a sumach (Rhus succedanea, etc.). At ordinary temperatures its specific gravity is exactly that of water, and it melts at 56° C. Any admixture with other fats would lower the melting point, but japan wax is often adulterated with 15 to 30 per cent. of water. It is chiefly valuable to leather dressers as a substitute for beeswax on account of its lower price.