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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 rnentioned, 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

this residual distillate contain much naphthaline, in which case it will solidify partially or entirely, and the solid part is rejected and the fluid part only of this residual distillate is added to the dead oil. The camphole, after this distillation, is now agitated either with common hydrochloric acid, or with dilute, sulphuric, or nitric acid, formed by mixing the strong acids of commerce with about six times their bulk in water. This agitation is continued for a convenient length of time, and may be done in an open vessel with a stirrer. Having allowed the fluids to separate, I draw off the acid, and then I sometimes repeat the agitation with a further quantity of dilute acid with the addition of some chloride of lime in the proportion of a quarter of a pound of chloride of lime to a gallon of the acid, but this may be omitted. The oil is drawn off and well washed with water, from which it is separated, and then rectified. It may be rectified by passing steam through it, or by distilling from a retort to which fire is directly applied, but in either case it is convenient to place between the retort and the condenser a vessel similar to the dry lime purifiers used for purifying coal gas, in which lime is placed on plates or gratings in a chamber having only two openings, so that the vapors pass over the lime, and I prefer to have this lime purifier of such size that it may contain lime conveniently spread in the quantity of about half a pound of lime, more or less, to a gallon of the oil placed in the retort, but a smaller vessel may be used. This vessel is so arranged that the vapor of the oil, or water and oil, as it leaves the retort, passes over the lime which deprives it of dry acid remaining in it, and then passing into the condenser is reduced to the fluid form. But I prefer to rectify it in a retort over fire directly applied without the presence of water or steam, and to use a thermometer inserted in the retort, and to cease receiving as camphole when the temperature in the retort reaches 190 degs. By this means I obtain the oil colorless, and it should be of specific gravity, .890 or .900, or if the distillation be not continued so far, the specific gravity may be so low as .870. Concentrated sulphuric and nitric acid, separately or mixed, may be used in the purification of camphole; but I prefer not to use such acids, as a considerable loss of hydrocarbon is thereby sustained, and the use of concentrated nitric acid sometimes confers a yellow color on the oil which it does not lose on rectification. I sometimes repeat this treatment with alkali and acid once or oftener. Camphole so purified is applicable, either alone or mixed with the common naphtha of commerce, or mixed with some of the oils having lower boiling points separated in my processes, or with the pyroxylic spirit for burning in lamps. It is also useful as a substitute for oil of turpentine in making varnishes.

For the purification of the dead oil I adopt the same method of digesting with an alkali as that which I have described for

camphole, but I prefer to use a stronger lye and in larger proportions, and to continue the digestion for a longer time before I change the outlet and commence distillation, since the dead oil contains a larger quantity of acid substances. The same description of apparatus and the same sorts of alkali are applicable to the dead oil as to the camphole, but caustic alkalies are much to be preferred to carbonates. And in rectifying the dead oil from which the camphole has been previously separated by distillation, which is that which I prefer to treat in this manner, though the Inethod is equally applicable to dead oil from which the camphole has not been removed after digestion with the alkali. If the lye be not drawn off, very little oil will be carried over with the water which distils off first, and whether the lye be or be not drawn off, I prefer to receive separately all the oil which comes over, betore the temperature in the retort reaches 200 degs., and if there be little naphthaline present, I add this oil to the camphole of the corresponding degree of purity. If there be much naphthaline present, I reject so much of that part of the distillate from the dead oil as solidities in the cold, which will be the case in some instances while the temperature is rising from 210 degs. to 220 degs., or even higher. And the quantity which it will be convenient to reject may be ascertained by observing whether a thin film of the distillate received on a cold surface solidifies, when the temperature in the retort is above 210 degs., when it ceases to solidify; on being so examined I commence to receive the mortuole for purification. If none solidify on cooling, I receive all the distillate above 200 degs. together, till the temperature in the retort reaches 280 degs. or 290 degs., I reject what comes over above as containing too much paranaphthaline. And, instead of treating the oil with dilute acid, I treat the dead oil, after distilling from the caustic lye, with oil of vitriol, in the proportion of one pound of oil of vitriol to one gallon of oil, and with or without the addition of a small quantity of nitric acid ; I agitate the acid with the oil in a suitable vessel for one or two hours

, and I prefer to allow the oil to stand with the acid for two or three days, and to repeat the agitation occasionally. I then draw off the oil from the acid, after having allowed it to settle. Finally I distil it through a dry lime puritier, as described for the purification of camphole. The oil should be collected in this rectification between the temperature of 220 degs. and 280 degs. This oil will be of a pale yel. low, or almost colorless. I sometimes repeat this treatment of the mortuole with acids and alkali, once or oftener.

* It is convenient sometimes further to purify the mortuole, camphole, and other oils, and spirituous substances, by filtering them through finely divided carbon, for which purpose I prefer animal charcoal or lampblack, which has been digested for a short time in oil of vitriol, or boiled in a solution of carbonate of potash, and then dried and heated to redness in a closed vessel

recently before use. And the filtration may be conveniently conducted by placing the oil in the filtering apparatus, over a vessel or receiver, into which the oil will be forced through the filterer by the pressure of the air, when the air is exhausted from the receiver. By further treatment with caustic alkali or lime, and with sulphuric acid, and by subsequent rectification, the mortuole may be obtained quite colorless. The oil so obtained is applicable to many of the purposes to which oil of turpentine is applied, and also to many of the purposes to which fixed oils are applicable, and it is applicable either alone or mixed with the more volatile hydrocarbons to burning in naphtha vapor pressure lamps, and when mixed with pyroxylic spirit in suitable proportions, to burning in lamps in which oil of turpentine or the fixed oils are burned.

What I here claim in respect to this second part of my invention, is the purification of the spirituous substances and oils which I manufacture from coal-tar, by treatment with chemical agents, according to principles laid down, depending on the nature of the spirituous substance and oils aforesaid, and of the impurities de. sired to be removed.

I also claim the use of nitric or nitrous acid, of nitro-muriatic acid, and of chromic acid, and the salts of those acids in the purification of empyreumatic and bituminous volatile oils, and the purification of certain of the oils manufactured from coal-tar by digestion with alkalies in the manner above described, and by distilling them so that their vapor is passed over lime, in the manner above described, and the purification of a spirituous substance obtained from coal-tar by congelation and pressure, which substance so purified I call absolute benzole.

Art. II.-GOLD ORES AND TIIEIR WORKING.

As the attention of those who are engaged in the working of gold ores, appears at the present time, to be more particularly directed to the mechanical appliances, by which the separation of the gold from the gangue-stone can be produced, than to the various descriptions of ore which are presented to their operations ; I have thought it the most advisable plan to follow, in these papers now submitted to the public, to give a brief description of the most common methods of crushing and amalgamating now in vogue, and also to show the principles which actuate such manipulations, and to endeavor to point out such adaptations of those principles, as appear to me to be the most likely to aid in obtaining such results, as the labors of those interested are endeavoring to produce.

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