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with fixed oil in any proportion: if the twofluids are ftrongly fhakcn together in a half-filledvial, the oil is broken into very minute globules,and thus gives the water the appearance of thinmilk or whey, but after {landing for a fewfeconds the whole of the oil rifes to the furface,and the two liquors remain as clear and diftinClas at firil. That a considerable attraction fub-iilts between water and oil is however manifeftfrom the well-known fact, that if a drop ofoil be let fall into a bafon of water, it does notretain its globular form, but immediately fpreadsitfelf into a thin iridefcent film with which thewhole furface of the water is covered.

The fixed oils are fo called becaufe they areincapable of being volatilized by heat withoutdecompofition: when therefore any of them,olive oil for example, is heated in a clofe diftil-latory apparatus, as foon as the fluid has arrivedat its boiling point a white vapour is difengaged,confiding of oil, carburetted hydrogen, andcarbonic acid; of thefe the firft is for the mollpart condenfed in the receiver, while the othertwo, holding a portion of oil in folution, efcapein the form of permanent gas; when everything volatile has been driven off, nothing re-mains in the retort but a little charcoal. Theoil which is found in the receiver is lighter,more limpid and volatile than that from whichit was procured, and thefe qualities are ob-lerved to increafe by each fucceffive diftillation,carbon and carburetted hydrogen being difen-gaged as at firft. By treating in this mannerthe product of each diftillation the oil at lengthentirely difappears, being partly decompofedand partly carried off in folution by the carbu-rutted hydrogen gas.

If oil inftead of being diftilled is heated in anopen kettle, its colour by degrees becomesdeeper, a highly inflammable and fetid vapourefcapes, and the remaining oil is found to bethick, vifcid, and when fpread over wood orany other fubftance and expofed to the air, con-geals into a folid, tough, tranfparent varnifh.In this ftate it is called boiled or drying oil.It has not been very fatisfa&orily {hewn whattakes place on this occafion, but it is probablethat the mucilage and fecula are for the moftpart charred and decompofed, that the waterwith which they were combined is volatilized,that a fmall portion of the oil itfelf is drivenoff, and that the refidue has abforbed fomeoxygen from the air. When oil is expofedto a high heat and at the fame time to, the freecontact of the atmofphere it takes fire, and

burns with a copious flame, accompanied by %thick black fmoke ; the combuftion of oil how-ever does not readily take place except bymeans of a wick: if an Argand lamp is ufedfor this purpofe the flame is of a pure whitecolour, and no fmoke is produced, the wholeof the oil undergoing entire combuftion. Inthis procefs the oil, according to Lavoifier, isconverted into water and carbonic acid, in fucliproportions, that its conftituent parts may beftated at 21 of hydrogen, and .79 of carbon.In this however no allowance is made for theoxygen which oil no doubt contains, fo that atbelt the given proportions can be looked upononly as a lonfe approximation to the truth.

It is known that fome of the fixed oils ("andprobably all of them) abforb oxygen, eitherfrom the air or from oxygen gas, at the commontemperature. Berthollet difeovered that oil ofalmonds in a jar half filled with oxygen gas{landing over water, had in the courfe of amonth abforbed nearly the whole of the oxygen,and at the fame time depofited a number ofwhite concretions forming a thin ftratum be-tween the water and the oil. In another experi-ment this able chemift expofed a very thin ftra-tum of oil on the furface of water to the contadlof atmofpheric air for three months : at the endof this period the oil was found converted intoa white concrete fubftance, friable at a low-temperature, but fufible at a leis heat than thatrequired for the melting of wax.* By longexpofure to the air fome oils, as olive oil, be-come rancid, in which ftate they exhibit thefollowing charafters: the colour is deepened,the odour becomes ftrong and difagreeable, theconfidence is vifeous or ropy, and vegetableblues are changed to red, {hewing the develope-ment of an acid. Other oils on the contraryin fimilar circumftances only dry to a toughvarnilh. The former are often called fat oils ,and the other fpontaneoufly drying oils.

Of the fimple Gombuftibles, hydrogen in theftate of gas is flowly and fparingly taken up byoil, but the effeft of this combination has notbeen examined. Charcoal appears to be whollyinfoluble in oil, but when newly burnt it hasthe property of bleaching and purifying it toa confiderable degree.

Phofphorus by the afliftance of heat is folublein oils though fparingly, and the compoundhas the property of becoming luminous iffmeared thin over any dry fubftance andexpofed to a warm air. A few drops of thephofphorized oil if rubbed on the hands or

* Mem. dc l’Acad. 17 95- f • 3*9-