The coal tar colours have nearly superseded those from lichens which incrust rocks, walls and stems of aged trees with brilliant colours, which do not however furnish dyes directly; they yield a colourless crystalline substance which combines with alkalies to furnish very beautiful dyes; it is exactly the opposite of rosaniline, which is a base. The Variolaria dealbata yields litmus or orchil, from which the beautiful French purple is made. The Rocella tinctoria and fusiformis give blue and purple, and the pale yellow lichen, Parmelia parcolerina furnishes a bright yellow dye, which a little ammonia changes to a rich red, inclining to purple. Mauve was first made from orchil, but was not permanent. The fine dyes, alizarine blue, Turkey red and garancine, are still much in use. They are derived from madder, the dried roots of the Rubia tinctorum; the madder dyes most extensively employed are alizarine and flower of madder. Mauve and other dyes are derived from guano, the offal of seabirds, which is imported in large quantities for manure.
The coal tar colours are manufactured on a highly scientific plan and most extensive scale in Great Britain, to supply the enormous quantity annually consumed in dyeing silk and printing cotton. In general, animal substances such as silk and wool can be permanently dyed at once, because they have a strong affinity or attraction for coloured dyes. If silk is destined to be a moiré, the silk before it is woven undergoes a chemical process in order to introduce fatty matter into it which gives a softness to the silk when woven and renders it fit to receive the moiré by intense pressure.
Cotton cloth has no affinity for dyes, which are washed out at once if not fixed by art, because cotton fibre consists of minute tubes generally open at the extremity, which imbibe the dye by capillary attraction, but cannot retain it unless fixed by a mordant, such as the white of a raw egg, which readily absorbs any dye that is mixed with it, and being then laid on the cloth in any pattern it is absorbed by the tubular fibres, and when coagulated by steam or any other application of heat it is immovably fixed. Both animal and vegetable substances afford a variety of mordants. Caseine or cheese, the curd of milk, which may also be obtained from pease and beans, is the mordant most used by calico printers; for if caseine be dissolved in twice the quantity of alkali necessary for its solution, it coagulates like white of egg and may be used in the same manner. Skimmed milk cheese from Scotland and Holland when purified is extensively used in calico printing. The quantity of mordants required is very great, for of all the cotton that was imported into Britain before the late American civil war, one seventh only was manufactured into muslin and printed calico, yet as already mentioned that was sufficient to envelope the earth’s equator nineteen times, and twenty-seven millions of pieces were exported annually. Atmospheric electricity and ozone affect the process of dyeing, and east wind has a retarding and injurious effect. The Lyons manufacturers, not less celebrated for their scientific skill and taste than for the brilliancy of the colours, have an advantage in their fine climate and bright sun.
It is a singular circumstance that petroleum has existed in enormous quantities throughout the North American States and a great part of Canada, unnoticed and neglected till the year 1859, when its value was discovered, and it almost immediately formed a new and extensive branch of commerce, for during the succeeding year at least 1,000 wells were dug, some of which enriched the proprietors; others were a failure.
Petroleum from the fountains of Is, on the banks of the Euphrates about 120 miles from Babylon, furnished the asphaltic mortar for building Nineveh 2,000 years before the Christian era. There are many sources of naphtha, petroleum, and asphalt in Europe and Asia, which like those in Trinidad and Venezuela occur for the most part in rocks of the newer, secondary and tertiary formations, though sometimes in the lower. But in the northern part of the United States and Canada these substances occur in rocks of all ages from the lower silurian to the tertiary period inclusive; they are usually found in the limestones and more rarely in the sandstones and shales. Petroleum collects in the fissures of the rocks, chiefly in those that have a tendency downwards; in wells dug for it near one another, an abundant supply is furnished at all depths from 70 to 300 feet. In some parts of Ohio and Canada the ground is saturated with petroleum, so that it is believed there is enough in North America to supply the world for ages. In 1861 no less than 42,000,000 gallons of petroleum were sent to England. The wells are not without danger, for when they pass through the coal strata, the petroleum is accompanied by a highly inflammable gas which on one occasion was accidentally set on fire; it ignited the petroleum, which was forced out as from the mouth of a volcano, and covered the ground with liquid fire far around; at the same time the burning gas formed an incandescent atmosphere which extended to a still greater distance.
The distillation of petroleum yields substances for the most part identical with those arising from the distillation of coal. The crude petroleum is put into an iron retort connected with a coil of iron pipes surrounded by cold water, called the condenser. Heat is applied to the retort, and from the open extremity of the condenser, a pale coloured liquid with a strong smell flows, which is very volatile and explosive naphtha. After the naphtha has passed over, an oil of excellent illuminating quality is distilled over. Steam is then forced into the retort, and a heavy oil is driven over, and there remains a black, oily, tarry matter, and a black cake used for fuel. After the naphtha has been repeatedly distilled, benzol is formed, and when the heavy oil is cooled to 30° Fahr., crystals of paraffin appear, which are separated from the oil by pressure, and when they are purified by alternate pressure and agitation in a melted state, they are moulded into candles. This paraffin is identical with that from coal. Among the products of the distillation of petroleum are naphthalin whence aniline is obtained, which yields mauve, magenta, and the other coal tar colours, also solferino which yields dianthine and other dyes and has been proposed as a substitute for chloroform and ether. Many other substances have been separated from petroleum which like some from coal have not yet been chemically examined. Most of the substances obtained from petroleum and the distillation of coal are common also to distilled peat, and now it is proposed to utilize sea weeds, in which the northern coasts of Scotland and Ireland are so rich. They were burnt for many years chiefly to furnish soda, but as that substance is obtained at a cheaper rate from salt, kelp or sea weed ashes has only been made lately to obtain iodine for medical purposes, and more than one half is wasted in the process. Besides iodine and six other substances generally procured from kelp, Mr. Stanford has discovered that it contains naphtha, paraffin oil and volatile oil rich in benzol, which yields aniline and magenta dyes and shows that marine vegetation as well as terrestrial abounds in colouring matter.
Every substance is now of use, no substance is without its value, but it would be a vain attempt to mention the innumerable discoveries made by experimental chemistry, which is daily extending its empire over the three kingdoms of organic and inorganic nature.
Composition of some of the preceding Substances.
| Acetylene | C2H2 |
| Olefiant gas | C2H4 |
| Ammonia | H3N |
| Benzol | C12H6 |
| Phenyle | C12H5N |
| Aniline | C12H7N3 |
| Rosaniline | C40H9N3 |
| Carbolic acid | C12H6O2 |
| Cressylic acid | C14HO2 |