posit so large a quantity of crystalline matter as to become almost entirely solid. It should have a smell somewhat like that of almonds. It will be found to be an excellent solvent for the same purposes as alliole, being very useful for making many kinds of varnishes. If a solution of gutta-percha be made in benzole, and the solution be spread as a varnish on a smooth surface, such as glass or porcelain, the spirituous parts will rapidly evaporate, and will leave the gutta-percha in a tough film on the surface, which must be peeled off, and in this way, by properly adjusting the surface and carefully peeling off the varnish, artificial membranes applicable to many useful purposes may be made, or by spreading the solution on the surface of the human body, an excellent plaster or artificial skin may be obtained in cases in which protection is desirable. This benzole is an excellent solvent for camphor, essential oils, fats, wax, and many other substances. It may be used as a substitute for spirits of wine in some of the arts, and for oil of turpentine in most of the purposes to which that hydrocarbon is applied, having the property of far greater volatility than the latter substance, which in many instances would be an advantage. Benzole admits, however, of yet further purification, which for some purposes it is desirable to effect, and this is accomplished by freezing. But since for those purposes for which it would be required to be so highly rectified, it would probably be required to be as free as possible from all foreign oily matters, I recommend that it be again treated with sulphuric acid, with or without the addition of saltpetre or nitric acid, or with nitric acid alone, or with nitro-muriatic acid, as above described, or that it be distilled with about one quarter its bulk of a mixture of two parts concentrated sulphuric acid and one part of a concentrated aqueous solution of bichromate of potash, or with a small quantity of chromic acid; and I recommend that such treatment be repeated until the benzole, on being agitated with cold oil of vitriol, no longer confers a dark color upon the acid; but strong nitric or nitro-muriatic acids must not be used in so large proportion as sulphuric acid may be used, since the benzole may be decomposed by the former acids, though not by the sulphuric acids.

When this further treatment with acid has been used, I wash the benzole well with water or with lime-water to remove the acid, and distil it either with or without the addition of some lime, and I prefer to insert a thermometer in the retort, and to receive for refrigeration what comes over, while the temperature in the retort is between 79 degs. and 88 degs. What comes over beyond may be mixed with some of the crude spirituous substances, reserved as purified toluole, of which it will partly consist. The benzole may be further rectified by distillation any number of times, and that portion of the distillate should always in that case be reserved separately for purification, which comes over between 80 degs. and 85 degs.

The reduction of benzole to a state of further purity, depends upon the property which it possesses and which distinguishes it from coal naphtha, and from all the other hydrocarbons contained in the naphtha, viz., that of becoming solid when exposed to a low temperature, and of melting again when pure at a temperature a little above that at which ice melts. The degree of cold requisite to solidify the fluid will vary inversely with the degree of purity which it has previously attained by distillation. If nearly pure it will solidify at U deg., if about half the fluid be benzole, and the rest the other hydrocarbons of the naphtha, which distil over with it, the benzole will crystallize out of the solution, when exposed to a temperature of 20 degs. And I may state that, generally, if the crude benzole obtained by once distilling the first runnings of the coal naphtha, or the whole light oil, or the rectified naphtha, as described in the first part of my invention, viz., from a boiler surmounted by a head surrounded with water, which is allowed to become heated to ebullition, be again rectified in a similar apparatus, and the first portion of the distillate equal to one-third the quantity placed in the retort (especially if the very first one-sixteenth portion be set aside separately as alliole, which does not solidify at 0 deg.), or if that portion which comes over while the temperature in the retort is rising from 80 degs. to 90 degs. be reserved as benzole, that portion so received on the second distillation will, if submitted to a temperature of -20 degrees, become in great part solid, depositing crystalline matter equal to at least half its bulk. By further rectification both of the mother liquor of the solid portion (that is, of that portion of the spirituous substance which is separated as fluid from the solid benzole after refrigeration), and also of the rest of the distillate on this second rectification, a further portion of spirituous substance may be obtained which will solidify at -20 degs. I now expose the benzole which has been prepared for refrigeration to a low temperature in a suitable vessel, and for the production of this low temperature I use, if it be necessary, a freezing mixture. When the benzole has been so congealed, I expose it to a powerful pressure, and the more powerful the pressure by which this separation is effected the purer will be the result, and the lower the temperature at which the operation of pressure is conducted, the larger will be the produce. The fluid pressed out is set aside, and after further rectification, if required, will yield another portion of solid matter by refrigeration.

The purification may be carried still further, either by again pressing at a temperature of 0 deg. the mass obtained by a first pressure, or by placing the mass in a funnel, and allowing it to melt slowly in the air, with the bulb of a thermometer immersed in the mass, reserving as pure that which remains solid when the temperature of the mass has risen to 0 deg. I call the substance so produced absolute benzole. It will be found to boil constantly

at 80 degs. or 81 degs. It will produce a state of intoxication if inhaled in the manner in which ether is used. It is an excellent substitute for ether, in many uses to which ether is applied, as for the solution of iodine, quinine, wax, and fatty and volatile oils. The next spirituous substance, or toluole, which when pure boils at about 110 deg., and which may be obtained in a state of partial purity by reserving the last portions which come over in the rectification of benzole, and the first which come over in the rectification of camphole, is purified by treatment with acids in the same manner as the benzole, but not by refrigeration. And I wish it to be understood, that by purified toluole, I do not mean a chemically pure hydrocarbon having a fixed boiling point, but I mean an oily or spirituous substance obtained from the coal naphtha, which will boil chiefly between 100 degs. and 130 degs. being so much of the naphtha as remains after separating on the one hand as much as possible of the spirituous substances that will yield a white flame with a current of air passed through them, and on the other hand as much as possible of the oily substances which will not take fire on the surface on the application of a lighted match, both being understood of the fluids at the ordinary temperature of the air.

Since all that applies to toluole as regards its purification, is also applicable to common naphtha, and to other bituminous and empyreumatic oils, such as petroleum, or native naphtha, the oil distilled from bituminous schist, &c., I will here state my method of purification as applied to coal naphtha, generally observing, however, that in the application of concentrated sulphuric acid to common coal naphtha, a certain proportion of oil is lost by the destruction of much of the cumole by the acid, I add to the naphtha, or toluole separated as above described, concentrated sulphuric acid in the proportion of about three quarters of a pound, and nitric acid or aquafortis in the proportion of about a quarter of a pound to a gallon of the naphtha or toluole, which has been previously carefully separated from water. I then agitate them well together in a suitable leaden or other vessel. The nitric acid need not be the strongest, that of specific gravity between 1.30 and 1.40 is suitable, and it need not be pure; the crude acid, known as nitrous acid, or the acid called single aquafortis, may be used.

I do not confine myself exactly to the proportions here given, or I use a mixture of nitric and hydrochloric acids, or nitromuriatic acid, or nitrate of potash or of soda, instead of nitric acid, in about the same proportions, with or without the addition of an equal proportion of bichromate of potash, or bichromate of potash without the nitrates; but if I use these salts instead of nitric acid, I prefer to use a rather larger proportion of sulphuric acid. Since the object is not to form definite chemical compounds, exact proportions are unnecessary; all that is requisite is to have

sufficient free sulphuric acid to dissolve the naphthaline, or a part of the naphthaline, in the naphtha, and not sufficient to dissolve much of the other hydrocarbons; to have sufficient free acid of any sort to dissolve all the alkaline oils (aniline, picoline, &c.) and to have enough of the oxidizing agents, sulphuric, nitric, or chromic acids, to convert at once all the coloring matter into new volatile products, and to have enough nitric acid to convert a small quantity of the naphtha into an aromatic oil, which leaves a slight fragrance in the naphtha when separated from it by subsequent distillation. After thorough agitation and subsidence, I withdraw the naphtha, and wash it thoroughly with a large quantity of water till all the acid is removed. It is advisable to separate the naphtha carefully from the acid before adding the water, otherwise certain compounds may be precipitated by the water from the sulphuric acid liquor, which may impair the purity of the oils. I then either agitate the naphtha with a solution of caustic lime, caustic soda, or caustic potash (preferring lime or soda to potash as being cheaper); and then either distil the oil with the alkaline fluid, or after removing it from the alkaline fluid in a still, to which fire is directly applied; or I rectify it by passing steam through it in the manner already known and in use; and when so distilling, I sometimes pass the vapor through a dry lime purifier, as hereafter described, when speaking of the purification of camphole. I then carefully separate the naphtha from water, and it is fit for use; or I sometimes allow it to stand, after agitation with chloride of calcium or chloride of lime, in vessels in which a small quantity of those substances has been placed, which removes the remainder of the water.

The toluole or naphtha so purified is applicable to the melting of varnishes, and to combustion in lamps, in which oil of turpentine or coal naphtha are usually burned, and also to burning in lamps when mixed with alcoholic or pyroxylic spirit; or to naphthalizing a current of heated air, so as to confer on it illuminating properties on being ignited.

The camphole, which is obtained by the rectifications of the last portions of the light oil, and the first portions of the heavy oils of coal tar, is purified in a different manner, since, firstly, it contains a large quantity of creosote and other acid substances, and secondly, a considerable portion of the hydrocarbon, which is required to be purified, is destroyed by treatment with concentrated nitric or sulphuric acids. And the method which I adopt to purify this oil is to digest it with a caustic alkaline lye, and to distil it so that its vapor may pass over lime, and to agitate it with hydrochloric acid, or with dilute nitric or sulphuric acids; and I prefer to treat it first with alkali for this purpose. In a boiler or retort with two apertures or necks, one of which is directly connected with the upper condenser hereinafter mentioned, and the other with the condenser of an ordinary still,

(which boiler I prefer to be of cast iron), I place the crude camphole with about a quarter its bulk of a solution in water of caustic potash or caustic soda of specific gravity about 1.150, or with a similar quantity of a solution of hydrate of lime in water, with an excess of fresh-slaked lime, or with dry caustic potash, or caustic soda, in the proportion of a quarter of a pound of the alkali to a gallon of the oil, or with caustic lime in rather larger proportions (the carbonates of soda and potash may be used, but they do not act so perfectly as the caustic alkalies or lime in the removal of the acid substances, and in the oxidation of the other impurities). The boiler or retort is surmounted with a vapor chamber, or head similar to that recommended for the rectification of benzole, it being so connected with one of the necks of the retort, that all the vapors condensed in it shall flow freely back into the retort. This head is kept surrounded with water as cold as possible, as the object of it is to condense all the vapors and return them to the retort; it may be connected by its other or upper opening with a still-worm to condense any vapors that may escape, or its other opening may be closed with a loaded safety valve. The oil and caustic lye being placed in the retort, the neck of the retort which is directly connected with the still-worm is closed, and that connected with the upper chamber is opened; fire is applied, and the aqueous solution is to be allowed to boil. The ebullition will continue for any length of time, if the condenser in the upper condenser be perfect, and even if a small quantity of vapor be allowed to escape condensation, the digestion will continue for a sufficient length of time. I allow this digestion to continue for five or six hours after ebullition has commenced. I then either lower the fire to stop ebullition, and draw off the watery solution through a pipe at the bottom of the boiler, and then close the neck connected with the upper condenser, and open the other neck of the retort which is directly connected with the still-worm, and then distil the oil over; or I change the outlet in the same way, and distil without first drawing off the lye. In the latter case, oil and water will come over together at first, and the temperature in the retort will not rise far above 100 degs. or 110 degs. till nearly all the water and a large quantity of the oil has come over; but if the water be drawn off, the temperature in the retort will soon rise rapidly to 140 degs. or 150 degs. before any fluid distils. I then sometimes set aside the first portion that distils over so long as samples taken in a small open vessel catch fire on the surface on the application of a lighted match, and I prefer to receive as camphole that which comes over subsequently till the temperature in the retort reaches 190 degs. The residue is distilled over, distillation being stopped when the temperature in the retort reaches about 300 degs., if it should rise so high before distillation ceases, and is mixed with the dead oil in the same stage of purification, unless