About 13 per cent. of 33° to 35° lye is passed through a rose into the oil, and is thoroughly mixed. As the oil loses its colour, samples are periodically taken for examination, and when flakes are found to collect and quickly subside, the operation is stopped and the mixture allowed to stand, the temperature being kept at the required point by means of a steam jacket, and being seldom allowed to exceed that employed in the acid treatment. After removal of the lye, the oil is repeatedly washed with warm water, without agitation, the temperature being maintained at 60° to 80° C. As much as fourteen times their bulk of water is required for the washing of heavy oils. When the effluent water is free from alkali, the oil is removed and clarified in flat open pans, fitted with steam jackets and steam coils, and having deepened bottoms to receive the deposited water. When the oil is slightly turbid, it is often passed through filters warmed by steam, but there is still some danger of renewed turbidity from the gradual separation of organic salts and of sodium sulphate. This is especially frequent in the case of the most viscous oils, and can only be prevented by extreme care in washing out the lye.

The following table indicates the character and proportion of various fractions which are in some cases obtained :

In other instances, the products are fractionated as follows:

At a large refinery, the following products are stated to be obtained :

The residue which is left in the stills after the distillation of the lubricating oils has a specific gravity of about 0·945, and is termed goudron.

The following description of the manufacture of lubricating oils in a refinery at Baku is given by J. Ljutyk1:

The residues from the kerosene distillation are pumped from the storage reservoirs into tanks, and are warmed to 70° C. in order that water and impurities may settle down. They are then ready for removal to the still, or into the preliminary heater. The stills are horizontal cylinders holding 8,000 kilos. of astatki, and the charge is worked off in twenty-four hours. Petroleum and waste products are used as fuel, the flames passing under an arch, then back along the bottom of the still into the side flues, heating the still to one-fifth of its height. The hot gases are then conveyed to the heater, and follow a similar course under this before escaping to the shaft, great saving of fuel being thus effected, and the astatki being warmed to about 130° C. before it enters the still. The steam employed is superheated by passing it through an iron coil, or through straight pipes, 5 to 7 centimetres in diameter, arranged in two or three pairs in a furnace. It is heated usually to 250° C., but sometimes to 300°. An excess of steam is used to prevent decomposition of the distillate, and it is passed first into a cast-iron cylinder, 0·7 metre high and 0.5 metre wide, to remove any condensed water. Until the right temperature is reached by the contents of the still, a tap is left open for the escape of the steam, but when the distillate is at 160° to 180° C., this tap is closed, and another opened. The steam then passes into the still, where it is discharged through perforations in the branches of a 1 pipe extending the whole length of the still, about 45 millimetres from the bottom. The perforations are 3 millimetres in diameter, and are on the under side of the tubes. Sometimes steam is used without previous superheating, and then four or more rows of perforated pipes are used for its distribution.

The still is provided with a goose-neck of iron or copper, or with a cast-iron dome about 07 metre high, connected by a pipe with the condenser. The latter form is preferable, as it is cheaper, and affords easy access to the interior of the still for cleaning and repairs. The distilled hydrocarbons pass with the steam into the condenser, which usually consists of a coil of lead or iron pipe in a wooden or iron vessel, through which a current of water is passed. In many refineries, however, the following form of condenser is employed. The Rigaer Industrie-Zeitung for 1883 (No. 21).

1

vapours pass from the still into a series of upright copper pipes connected by cast-iron U-joints, and exposed to the air. To the bottom of each of the lower U-pieces is connected a coil condenser placed in a water tank, the delivery end of the pipes being carried up to the height of the first coil, and then passing out of the tank into the oil receiver. From the air condenser the uncondensed vapours are conducted into an ordinary coil condenser, and the distillate, with the condensed water, is collected, the incondensable gases being allowed to escape. By the use of the air and water condensers, the products of the distillation are fractionated according to their boiling points.

The process of distillation is as follows:-The requisite quantity of astatki is transferred from the heater to the still, and the temperature raised to 160° or 180° C., at which point the steam is carefully turned on. The density of the distillate is tested from time to time by an areometer, and the fractionating is thus regulated. Towards the end of the operation, when the oil coming over is of 0.915 to 0.920 specific gravity, the fire is put out, and steam alone is used, and as soon as a sample shows but little oil compared with water, this too is stopped, and the still allowed to cool down for two or three hours, after which the residue is removed. If a larger yield of the heavier oils is desired, the still is cooled as soon as the distillate is of 0.912 specific gravity, recharged with astatki from the heater, without removing the residue, and the distillation conducted as before.

The first fraction, which has a specific gravity of 0.865, is sold as gas oil, or is used in the refinery. The second, of specific gravity 0.875, is sold as cloth oil for oiling wool. The distillates having densities of 0.885 and 0.895 are mixed in equal proportions and sold as spindle oil. Those of specific gravity 0-895 to about 0.910 are worked up into machine oil, and those of above 0.910 specific gravity into cylinder oil.

To produce an odourless oil of pale colour, chemical treatment and redistillation are sometimes employed. The spindle-, machine-, and cylinder-oil distillates are mixed together and allowed to stand for a couple of days for the water to settle out, after which they are placed in an agitator and treated with sulphuric acid (5 to 10 per cent. of the weight of the distillates), the mixture being agitated by the use of an air blast, until a sample exhibits the presence of small black specks. After standing one or two days the oil is neutralised with warm quicklime, the lime being gradually added, and agitation continued until the oil is pale yellow in colour, and gives a weak alkaline reaction with litmus. To separate the gypsum, the oil is warmed to 70° and filtered. The oil, now of a light reddish tint and faint smell, is redistilled in a vertical-cylindrical still.

The following description of the processes adopted in the refining of "perfumery" and "mixing" oils is given by F. A. Rossmässler:

The distillation product of Russian petroleum residuum, known as solar oil, is redistilled, the lightest fractions, which are strong smelling, being rejected. The remainder of the distillate is freed from water by 1 Die Petroleum- und Schmierölfabrikation, 77 to 80, 1893. Leipzig.

blowing air through it at a temperature of 70° C., until it becomes bright, and remains so on cooling. The distillate is then subjected to the acid treatment, the first stage of which consists in the addition of 1 to 1 per cent. of ordinary sulphuric acid. The "sludge acid" having been separated, 10 to 15 per cent. of strong acid-fuming sulphuric acid, or a solution of sulphuric anhydride in ordinary acid in the proportion of 1 part of 80 per cent. anhydride to 2 parts of acid -is added and agitated with the oil for an hour to an hour and a-half, during which time the temperature rises to 35° to 40° C., with evolution of sulphurous acid. The "sludge" is then removed, and the oil treated with caustic soda solution (20° B.) until faintly alkaline. After removal of the soda sediment, free steam is blown in until the temperature rises to 45° to 50° C., the oil being then left to settle. The aqueous liquid having been drawn off, the oil is repeatedly washed with warm water, air is then blown through it while it is at a temperature of 40° C., and the refining is completed by filtration through bone black.

Properly refined perfumery oil has a specific gravity of 0.880 to 0-885, is quite colourless and inodorous, without fluorescence, and should not turn yellow or deposit sediment after prolonged exposure to direct sunlight. The finest quality is used in pharmacy as paraf finum liquidum, and for this purpose is frequently subjected to a final distillation. Mixing" oils are also prepared from solar-oil distillate, the fractions of a lower specific gravity than 0.860 being rejected, and only those having a specific gravity between that figure and 0.885 being employed. It is not essential that these oils should be perfectly colourless and non-fluorescent, and they are usually made in two qualities, the one "white," with a tinge of yellow, and the other a pale sulphur colour. Treatment with 5 to 8 per cent. of fuming sulphuric acid (after the preliminary acidification with 1 per cent. of English acid) suffices. The subsequent processes are similar to those employed for the perfumery oil. The chief use of the mixing oils is stated to be in the manufacture of "artificial olive oil." The pump for supplying compressed air for the drying process, must be so situated as to ensure the highest possible degree of dryness in the air blast, and should be heated in the cold season, damp air being prejudicial, as diluting and weakening the acid, and retarding instead of facilitating the drying of the finished oil.

The following has been recently given as the approximate average cost of the manufacture of kerosene in Baku in the case of those refiners who have their own wells:

Crude oil, 3 poods at 2 copecks, .

Cost of refining, including fuel, chemicals, establish-
ment, expenses, &c.,

Value of astatki, 14 poods at 4 copecks,

Net cost of 1 pood of kerosene delivered in tank wag-
gons at the refinery,

This corresponds to about a halfpenny per gallon.

The author is indebted to Dr. Dvorkovitz for the following particulars of the cost, under conditions which may be held to apply to the chief firms engaged in the industry :

TABLE XLI.-COST OF REFINED OIL (KEROSENE), 1894.
(a) Cost of Crude Oil.

1. Cost of drilling 12,612 sagenes in the course of the year 1894, .
2. Royalty, cop. per pood, or, for 304,000,000 poods produced in 1894,
3. Cost of administration, labour, &c., 1 cop. per pood,
4. Cost of pumping to the refineries and storing at the wells and
refineries,cop. per pood,.

Roubles. 3,153,000 1,520,000 3,040,000

1,520,000

(b) Cost of Manufacture.

1. Administration, labour, depreciation, &c., 2 cop. per pood, or, for 75,000,000 poods of refined kerosene,

1,875,000

2. Refining (caustic soda and sulphuric acid), 2 cop. per pood of refined oil, or, for 75,000,000 poods,

3. Storage of the refined products, pumping to the station, office expenses, &c., 1 cop. per pood,

4. Storage for 210,000,000 poods of residuals and crude naphtha for exportation, at cop. per pood, .

Total,

Less-193,600,000 poods of residuals at 4 cops.,

16,400,000 poods of crude naphtha at 33 cops.,

Net cost of 75,000,000 poods of refined kerosene,

1,500,000

750,000

1,575,000

Or 8.8 copecks per pood, or 0.63d. per gallon.

At the Petroleum Conference held at Baku in 1886, the undermentioned classification of Russian petroleum products was adopted :

1. Benzine-two sorts, viz.:

(a) Light benzine-colourless; used for manufacturing india-rubber goods, and distilled at a temperature not below 130° C. or 266° F.

(b) Heavy benzine-of a pale yellowish colour, yielding 10 per cent. refuse when distilled at a temperature as high as 150° C. or 302° F.

2. Kerosene-specific gravity 0.830; two sorts :--
(a) Safe-flashing point not less than 25° C. or 77° F.
(b) Unsafe-flashing point below 25° C. or 77° F.

3. Astralin-specific gravity 0-850; of a pale yellowish colour; flashing point less than 50° C. or 122° F.

4. Solar oil-specific gravity above 0.850, but not exceeding 0.880; flashing point not below 80° C. or 176° F.; may be of very pale yellowish colour.

5. Lubricating oils-specific gravity from 0-880 and upwards.

6. Crude oil-specific gravity from 0.850 to 0.880; flashing point below 70° C. or 158° F.

7. Mazut, or crude oil deprived of volatile light substances by exposure to air -specific gravity above 0.880; flashing point above 70° C. or 158° F.; and residue, locally called "astatki," flashing point not below 140° C. or 284° F.

8. The different petroleum products in a solid state-asphalt, ozokerite, &c. 9. Ceresine, paraffin, vaseline.

10. The different greases, varnishes, and mastics derived from petroleum.

The kerosene shipped by Nobel Brothers to the United Kingdom usually has a specific gravity of about 0·824 at 60° F., and a flashing point of about 86° F. (Abel test).