Jirtv i, 1884.J 



THE TROPICAL AGRICULTURIST. 



77 



of X 40° 0. It contains, if not freed from acids by alkal- 

 ies, besides tbe neutral fats, from 1 to 5 per cent of sebacic 

 acid. In examining tallow, care should be taken to ascert- 

 ain whether it is free from cellular tissues, free from 

 mineral acid, as well as extraneous additions (other fats, 

 sebacic acid, mineral substances, &c). 



Train-oil. prepared from the fat of seals, &c, in a man- 

 ner similar to tallow, forms, at an ordinary temperature, a 

 liquid of light or dark brown color and of a peculiar odor, 

 solidifying at a temperature of from X5° toX15° C. 

 As a rule it contains a large proportion (up to 5 per cent) 

 of sebacic acid. The same care should be observed in ex- 

 amining train-oil, as is recommended in the case of tallow. 



Olive oil is obtained by pressure from the fruit of the 

 olive tree, cultivated largely in the South of France and 

 Italy. It forms a beautifully yellow liquid of a peculiar 

 odor, and a mild taste, which begins to get thick at a temp- 

 erature of X 2° 0. The contents of free sebacic acid is 

 very small in the better descriptions; inferior sorts con- 

 tain about 05 to 1 per cent. 



Rapeseed oil or rape oil is procured from the seed of the 

 various kinds of Brassica, the seed being crushed in power- 

 ful hydraulic presses. The oil thus obtained is a yellowish- 

 brown to brownish-green liquid, of a peculiar odor and a 

 pungent taste, which precipitates the mucilaginous substances 

 of the seed which have passed in pressing only after being 

 kept in store for some time, and becomes clear b\ this 

 precipitation. But even perfectly clear oils contains mucil- 

 age or albumen in chemical solution, and these can only be 

 removed by treatment with chemicals or by heating up to 

 2U0° 0. The raw oil only cleared by storing was, and is 

 still, used for lubricating bearings, especially railway axles. 

 The purified oil, prepared by removing from the raw oil the 

 mucilaginous and albuminous constituents by sulphuric acid, 

 chloride of zinc, &c, and the free sebacic acid (on the aver- 

 age of CM per cent.; by treating with alkalies, is reserved 

 for lubricating the more delicate portions of machinery 

 and locomotives, steam cylinders, &e. The perfectly 

 purified rape oil, and from which all acid has been eliminated, 

 is of a light yellow color, almost odorless, possesses a speci- 

 fic gravity of from 0-914 to 0'915 at 15° C„ solidifies at a 

 few degrees below zero, and melts again at about X 3 ° 0. 

 In testing rapeseed oil, it must be ascertained whether it 

 possesses the correct specific weight and rneltiug-point, ;md 

 whether it is free free from mucilage, sebacic and mineral 

 acids. 



Palm oil and coconut oil are obtained from the fruit of 

 the oil and coconut palms respectively, imported in large 

 quantities into Europe. The fruit is either crushed in hydr- 

 aulic presses, or the oil is extracted by means of sulphuret 

 of carbon. The two oils or fats (for at an ordinary tempei - 

 ature they resemble butter) are now used very little for 

 lubricating purposes, but extensively in the manufacture 

 of soap. 



Resin oil, gained bv distilling the common resin obtained 

 from the residue left in the manufacture of oil of turpent- 

 ine from turpentine, was formerly used only in the prepar- 

 ation of " carriage grease," mixtures of this oil with colop- 

 hony, fats, &e. Refined resin oil is now procured by freeing 

 ■ the crude oil by means of alkalies, and subsequent bleach- 

 ing, the product being a clear semi-liquid of yellow color, 

 possessing but a slight odor, and having a high specific 

 gravity (about 0'970). The oils are never perfectly free from 

 organic acids, most of them containing about one per cent. 



The class of mineral oils includes a number of lubricants 

 which have nearly all a common origin with " petroleum.'' 

 Crude petroleum, as it was first won in large quantities in 

 America (since 1859), consists of an intermixture of many 

 organic substances, which, on account of their exterior 

 similarity to real oils, as well as for simplicity's sake, are 

 called " oils." These oils, which may be distilled without 

 decomposing, differ from each other by their various specific 

 weights, as well as by their various boiling points. Fur 

 a long time the volatile ingredients only were extracted 

 from crude petroleum, which were used for illuminating 

 purposes, whilst little attention was paid to the heavy 

 oils which remained after distillation. But when those re- 

 sidues grew in quantity, means had to be devised for utilizing 

 them, and it was soon found that they coidd be used as 

 lubricants. At first the oil was applied in its original form, 

 as bft in the alembic, in which it still contains many im- 

 purities. But now in most cases, after the more volatile 



oil used for lighting purposes has been distilled Over (at a 

 temperature of from 150° to 350° ('.), Hi.' lubricating oil 

 is also driven over. The latter is then purified with acids 

 and alkalies, and a product obtained which, in consequence 

 of its impurity, chemical constancy and .other valuable pro- 

 |i< rties, appears very suitable for use as a lubricant. 



As the raw mineral oil consists of a large variety of com- 

 binations related to one another, and as those combinations, 

 according to a greater or less degree of distillation, &c, may 

 appear in the most various mixtures, it follows that, inde- 

 pendent of their greater or less degree of purity, the mineral 

 oils may possess widely varying properties principally of a 

 physical nattire. Thus the color of the different mineral 

 oils varies from light yellow to dark brownish red; their 

 specific weights fluctuate between 0'880 and 0-920 ; their 

 cohesion — their "body," as more generally expressed — 

 shows itself in all grades between the consistency, for in- 

 stance, of the highly liquid linseed oil, when fresh, and 

 the semi-liquid resin oil, &c. But, however much their 

 physical properties may vary, in their chemical nature 

 mineral oils are closely related to each other. They all 

 consist (of course, only real mineral oils are included) of 

 a.mixture of carburetteel hydrogen, indifferent organic combin- 

 ations, which possesses neither acid nor basic properties. 

 They do not decompose either at very low temperatures or 

 at degrees of heat which far exceed those prevailing in 

 the steam cylinders, &c, where they are employed. They 

 do not undergo any change either on cuntact with the air 

 or with water or steam ; they do not attack metals, even 

 the most easily oxydisable, such as potassium or sodium, 

 and are as little changed or deeomposed by the metals 

 themselves. 



This chemical indifference is the principal advantage pos- 

 sessed by mineral oils over all fat oils, whether they are of 

 vegetable or animal origin. All those tat oils decompose 

 in time on exposure to the air, at high temperatures, on 

 contact with metals or their oxides, and thus destroy, some- 

 times more quickly, sometimes more slowly the parts of 

 machinery which they are intended to preserve. 



Notwithstanding those great excellences which mineral 

 oils have over fat oils, great difficulties were at first ex- 

 perienced in introducing lubrication with the former more 

 generally. Convenience, attachment to custom, and want 

 of intelligence were amongst the obstacles which had to 

 be overcome. Mineral oils were looked upon as entirely 

 unsuitable for lubricating machinery, and fat oils as alone 

 possessing the specific property of a lubricant ; apprehensions 

 were raised as to the " easy inflammability " of mineral oils, 

 &c. But the introduction of mineral oils for lubricating 

 purposes was also greatly retarded by the want of sense, 

 and partly also by the want of honesty, on the part of the 

 individual producers aud dealers. Properties were claimed 

 for the crude mineral oil only possessed by carefully puri- 

 fied oil ; when finally the price of lubricating oil exceeded 

 that of the oil used for burning, part of the latter was left 

 in the lubricant, so that, especially if great pressure took 

 place, it was found unsuitable. Norwithstandiug all this, 

 lulu. cation with mineral oil has, within the short space of 

 the last five years, made such progress that it may justly be 

 called, not only the lubricant of the future, but that of 

 the present day. As the mineral oils on account of their 

 chemical properties are far more valuable than fat oils, and, 

 on the other hand, owing to greater variety physically, they 

 may be adopted more readily for different purposes than 

 fat oils, there is nothing to preveuttheirgeneial introduction. 



It will be gathered from the foregoing that the displace- 

 ment of fat oils for lubricating machinery by mineral oils 

 is a great technical progress. But the use of mineral oil 

 is a great advantage also from the point of cheapness. The 

 best mineral oils are now oidj r half the price of fat oils. 

 AVith a suitable construction of the parts to be lubricated aud 

 a correct choice of the most suitable lubricating materials, 

 the consumption of mineral oils is not greater ; on the con- 

 trary, it ought to be less, as with mineral oil no hardening 

 or thickening takes place, and thus there is no loss. Finally 

 in lubricating with mineral oil, the parts oiled are not de- 

 stroyed, but, on the contrary, preserved ; whilst the destruc- 

 tion of machinery parts, such as pivots, regulator valve- 

 re ds of locomotives, &c, is only too often a consequence 

 of the use of fat oils. 



I'.nt the ultimate introduction) of lubrication with mineral 

 oils is of importance also from an economical point of view. 



