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uses the uncorrected chromolithograph in the new edition of his "Qualitative Analyse," and we have never yet had the good fortune to see the lines of this element correctly mapped on any coloured print.

Bunsen notices at length the inaccuracies of the diagram of Johnson and Allen, which, as the latter stated distinctly, was intended to give approximatively the position of the lines on Kirchhoff and Bunsen's scale, and which from the construction of the spectroscope they employed would not be exact.

The remark of Johnson and Allen that their "line II., nearly coincident with a lithium of Kirchhoff and Bunsen, and not figured by them, is as bright as their y caesium, our VI. (?)"-Bunsen passes over without notice. The observation is certainly not an unimportant one, for any person occupied in preparing the new alkalies is likely to be embarrassed by a line that in small instruments is practically coincident with a lithium, if it be not credited to cæsium by the authorities.

Johnson and Allen rightly state that "the yellow line VIII. is hardly less characteristic of the spectrum of pure cæsium than the two blue lines. It also is nearly as distinct as any of the green lines when sodium is not present in too large quantity, and is much more readily made out than the extreme red line & of rubidium." This line was wanting in the original spectrum plate of Kirchhoff and Bunsen. Chemists will be glad that Bunsen has now given, in connexion with the paper we refer to, a diagram of the spectra of all the alkalies and alkaline earths, as well as of thallium, which is quite complete, and which, by following his simple directions, is readily and exactly comparable with the spectra of any instrument. In this he figures sixteen lines for cæsium.-S. W. J., in American Journal of Science, Xxxvi., 413.

TECHNICAL CHEMISTRY.

Account of an Oil-Lamp Furnace, for Melting Metals at a White Heat, by CHARLES GRIFFIN.

I HAVE been for some time engaged in experiments on the construction of chemical lamps. My object was to discover a method by which chemists and metallurgists, who have occasion to melt metals at a white heat, but who happen to have no command of coal-gas, may be enabled to accomplish their purpose by other agents.

FIG. 1.

Preparation of Chloropicrin, by SAMUEL PRIESTLEY. THIS substance, which has usually been prepared by distilling picric acid with hypochlorite of lime, may be establishes beyond doubt the connection of chloropicrin prepared from methylic alcohol directly-a fact which with the methyl series.

manner :I succeeded in obtaining the substance in the following

Bleaching powder is introduced into a flask, with as the materials, the flask must be placed in a shallow basin much methylalcohol as will form a paste. After mixing of cold water, in order to prevent the volatilisation of the spirit by the heat disengaged.

When the chemical action has subsided, nitric acid is added carefully and by small portions at a time, allowing the action to subside each time, the flask remaining still in the water.

The whole, when dissolved, is submitted to distillation.

During the distillation a gas is evolved, which burns with probably chloride of methyl, but I have not examined it a green flame, and may be collected over water. It is further. These product which collects in the receiver appears to be a mixture of chloroform, chloropicrin and wood-spirit. These substances are afterwards separated by distillation; the chloropierin, having a higher boiling point, remains behind.

In the actual reaction it is very probable that chloroform is first produced, and that the nitric acid reacts according to the following equation:

H

CHCI, +N, O=CNO,Cl,+ NO2

H

H

The odour and oily appearance of the substance leave no doubt as to its true chemical nature.

* Carbon = 12. Oxygen = 16.

After many trials, I have contrived an oil-lamp which is not only as powerful in action as the best gas furnaces, but almost rivals them in handiness and economy.

Description of the Apparatus.-The oil-lamp furnace is represented in perspective by Fig. 1, and in section by Fig. 2. It consists of a wick-holder, an oilreservoir, and a fire-clay furnace. To these must be added a blowing-machine for the supply of atmospheric air.

The oil-reservoir is represented at letter a. It is made of japanned tinplate, mounted on iron legs, and fitted

FIG. 2.

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pressure by a dozen blowpipes, in effective contact with the crucible to be heated.

The flame produced in this furnace is as clear as that produced by an explosive mixture of air and coal-gas. It is perfectly free from smoke; and the unconsumed vapours which occasionally escape with the gaseous products of the combustion are even less unpleasant to smell and to breathe in than are those which are usually disengaged by a blast gas furnace, or by an ordinary lamp fed with pyroxylic spirit. The contents of a crucible under ignition in this furnace can at any moment be readily examined, it being only necessary to remove the pieces and m with tongs, and to lift the cover of the crucible, during which the action of the furnace is not to be interrupted.

When the operation is finished, the blast is stopped, the stopcock is turned off, the oil-reservoir is removed, the wick-holder is lowered on the support o, withdrawn from the furnace, and covered with the extinguisher n. The quantity of oil which then remains in the lamp is

about one fluid ounce.

Power of the Oil-Lamp Furnace.-The furnace being cold when an operation is commenced, it will melt 1 lb. of cast iron in 25 minutes, 1 lb. in 30 minutes, 4 lbs. in 45 minutes, and 5 lbs. in 60 minutes. These results have been obtained in my experiments. When the furnace is hot, such fusions can be effected in much less time; for example, 1 lb. of iron in 15 minutes. It need scarcely be added that small quantities of gold, silver, copper, brass, German silver, &c., can be melted with great ease, and that all the chemical processes that are commonly effected in platinum and porcelain crucibles can be promptly accomplished in the smallest cylinder of this furnace; and, in the case of platinum vessels, with this special advantage, that the oil-gas is free from those sulphurous compounds, the presence of which in coal-gas frequently causes damage

to the crucibles.

Requisite Blowing Power.-The size of the blow

I

ing machine required to develop the fusing power of this oil-lamp furnace depends upon the amount of heat required, or the weight of metal that is to be fused. For ordinary chemical operations with platinum and porcelain crucibles, and even for the fusion of 1 lb. of cast iron in clay or plumbago crucibles, a blowing power equal to that of a glass-blower's table is sufficient, provided the blast it gives is uniform and constant. But the fusion of masses of iron weighing 4 or 5 lbs. demands a more powerful blower, such as is commonly used in chemical laboratories for the supply of air to blast furnaces when fed by gas or coke. The highest power of the oil-lamp furnace depends, indeed, upon the power of the blowing-machine that is to be used with it. Much more than 5 lbs. of iron can be melted by the gas which this oil-lamp is capable of supplying, provided a sufficiently powerful blowing-machine supplies the requisite quantity of air. When more than a quart of oil is to be rapidly distilled into gas, and the whole of that gas is to be instantly burnt with oxygen, it is evident that effective work demands a large and prompt supply of air.

Cost of the Oil-Lamp Furnace.-As in all practical matters of this sort the cost is a main question; it may be useful to state that the price of this apparatus, complete, without the blowing-machine, but including every other portion necessary for heating crucibles up to the size sufficient to fuse 1 lb. of cast iron, is one guinea; and that with the extra furnace-pieces for crucibles suitable for 5 lbs. of iron, or any intermediate quantity, the cost is a guinea and a half.'

PHARMACY, TOXICOLOGY, &c.

On Spiritus Ammoniæ Aromaticus, by W. T. FEWTRELL, F. C.S. AROMATIC spirit of ammonia, commonly called sa volatile, is directed by the Pharmacopoeia to be made with such proportions of carbonate of potash and chloride of ammonium as it is supposed will produce a neutral carbonate of ammonia in solution in a mixture of spirit sometimes happens with the most meritorious designs, of wine and water, with flavouring substances; but, as it would seem that the purpose intended is not always fulfilled. It should have been premised that it is with and it now almost requires an apology for noticing this the spirit of the Pharmacopoeia of 1851 we are dealing; article. Whatever apology, however, may be necessary, has been recently supplied by a contemporary. The formula about to be introduced by the British Pharmacopoeia will be noticed in due time: for the present we return to the Pharmacopoeia of 1851.

In this work we find the following recipe :-Take of hydrochlorate of ammonia, six ounces; carbonate of potash, ten ounces; cinnamon and cloves, bruised, of each fied spirit and water, of each four pints; mix, and distil two drachms and a half; lemon peel, five ounces; rectisix pints. The result of this process is stated by Pereira and Royle to be the production of chloride of potassium, and neutral carbonate of ammonia, which latter distils statement is really true, and what the distilled product over with spirit, water, and essential oils. How far this contains, remain to be seen.

66

The Pharmacopoeia continues-" Hujus pondus specificum est"-("formula," as a recent novelist writes)'918." asserted, which in practice it is found almost impossible We have here again an invariable specific gravity

to secure.

We are, of course, well aware that sal volatile is often made by private formula; and that some which enjoy the highest repute are made by other than the Pharhas tended to swell the records of mortality greatly; macopoeia process. We do not suppose that this fact but we must not be supposed to defend any deviations from the authorised formula.

In some instances, respectable druggists keep two preparations: one made according to the Pharmacopoeia for dispensing; and another made for retail, more pungent, as suiting better the public taste.

We confine our notice to the preparation made exactly according to the Pharmacopoeia, and the question to be determined is, in what state is the ammonia in that preparation? Is it really monocarbonate, or does there exist, in a genuine Pharmacopoeia preparation, any free

ammonia?

In order to determine this point, four times the proportions of the Pharmacopoeia were distilled, so as to produce an article made on a manufacturing scale. The distillation was effected in an earthenware retort;

Spt. Am. Aromaticus.

and, as the use of a worm are liable to inconveniences, the product was condensed in two globular condensers set perpendicularly in separate vessels of water, and connected by means of an earthenware tube. The vessels were kept cool by a current of water passing in at the bottom and out at the top.

Small samples of every half-gallon of the product were taken as it came over. For the information of those

fore, consider it to be one of the constituents of the solid crust of the earth.

The geologist everywhere meets with problems of the highest interest which chemistry alone can solve; yet it is somewhat surprising that in this country of geologists the application of chemistry to the solution of geological phenomena should hitherto have received so small a share of attention. Geology, it must be admitted, is a most comprehensive science, and, to be studied as a whole, requires knowledge so varied and so extensive that there is, perhaps, no living geologist who can be said to have mastered the subject in all its details. It demands more than a superficial acquaintance with physics, mechanics, inorganic chemistry, mineralogy, comparative anatomy, and botany. Where is the man who possesses this combination of acquirements? Not a few persons have attained the reputation of geologists who have either been ignorant of the great foundations of the philosophy of geology, or have had a very slight knowledge of the subject. To know and to remember the order of superposition of rocks, and to be able to recognise the fossils which they respectively contain, does not, I apprehend, entitle a man to rank as a philosophical geologist. As well might a taxidermist lay claim to the title of zoologist, or an ornithologist to the title of botanist. The conquests which remain to be achieved in geology will, doubtless, result from the special study and application of the various sciences which essen. tially compose the great science of geology, and there is assuredly no line of investigation which promises richer fruit than that relating to chemistry.

Having made these preliminary remarks, we will, if you please, proceed at once to examine the subject of this morning's lecture. That subject is silicon, perhaps the most abundant, or, certainly, one of the most abundant elements in the solid crust of the earth. This silicon has only recently been investigated in anything like a satisfactory manner. It exists in, and is the foundation of silica in its various forms. Silica exists in the well-known form of quartz, and consists of silicon combined with oxygen. In sand and in all clay, and in igneous rocks of various kinds, it is an essential constituent. In fact, it is everywhere. This silicon, when once united with oxygen, requires an extraordinary amount of affinity, or the exercise of an extraordinary force to detach it therefrom.

Silicon exists in three distinct states, the amorphous or formless state, in the graphitic state, and in the state of crystallised octahedral silicon. I have here placed before you some very fine specimens of silicon, for the loan of which I am indebted to Mr. Matthey, of Hatton Garden. They are as fine as can well be seen. I shall not attempt to describe the substances which are prepared from silicon, as that would occupy too much of our time.

In its three states, silicon differs considerably. In the amorphous state it occurs in the form of a chocolate brown powder. In the graphitoidal state it is exactly like graphite, or very similar, occurring frequently in small hexagonal plates, as produced in the process for making aluminium. Then we have the octahedral form, the same form and the same crystalline system as that to which the diamond belongs. But here it is a most beautiful substance, of a metallic lustre, and a dark bluish grey colour, considerably more blue then ordinary graphite, and, I think, more metallic in lustre.

Silica consists, in round numbers, of about 48 parts of this silicon, and 52 of oxygen. The atomic formula adopted, and first suggested by Berzelius, is this, Si O,, representing one equivalent of silicon combined with three of oxygen; but there are reasons for supposing that the more accurate expression is Si O2, one equivalent of silicon combined with two of oxygen.

Now, long ago it was ascertained by Schafgotsch that silica exists in two very different states. In one state it was crystallised as quartz, having a specific gravity of 2.6. All quartz, for example, has this specific gravity, and not

only quartz, but chalcedony, hornstone, and flint, and yet these present no outward sign of crystalline structure. It is, however, maintained by Rose, and with some plausibility, that they consist of an aggregation of excessively minute crystals. He designates these forms of quartz as crystalline, in contradistinction to the ordinary form of rock crystal, which is distinctly crystallised. We have, then, crystalline quartz, and this apparently non-crystallised form of quartz which I have just mentioned, chalcedony and the like, of the high specific gravity 2.6. Now, there is another form of silica in which the specific gravity never exceeds 2.3. It ranges from 2.2 to 23, and is never higher than that. This is what is termed amorphous, apparently non-crystalline silica; and these facts, you will perceive directly, have or may have a very important bearing on certain geological considerations of the highest importance. All the crystallised silica of the high specific gravity polarises light. The amorphous silica of low specific gravity does not polarise light. The distinctly crystallised silica which we have here in the form of quartz, when pulverised, reduced to extremely fine powder by trituration and levigation, does not differ chemically in any sensible respect from the powder of the apparently amorphous form of silica, flint, chalcedony, and the like. Both resist the action of boiling alkaline solutions, whereas the amorphous silica is copiously and readily dissolved by such solutions. The crystallised silica is produced in the wet way, and, so far as we know, only in the wet way. By the wet way, I mean through the agency of liquids, never by fusion at a high temperature. The late M. Senarmont, who has devoted considerable attention to the artificial formation of minerals, made microscopic crystals of quartz by dissolving silica in the nascent state, that is, at the moment of its separation from a state of combination, in very dilute hydrochloric acid, and then exposing that solution in a closed tube to a temperature of between 2co and 300 centigrade. These crystals he found to be precisely similar in crystalline form and all other essential respects to those actually occurring in nature, being in the form of six-sided prisms, terminated by the usual pyramids found in crystallised quartz, and having hexagonal faces presenting the transverse striæ which we so constantly see on these crystals. Here, then, is a clear experiment proving the production of crystallised silica by the agency of liquids, exactly similar, in all essential respects, to the rock crystal of nature. It is true that the crystals were very small; but that in no way affects the truth of the conclusion to which I shall draw special attention by-and-by; but all this crystallised silica, of which you have such a fine specimen before you, has been produced in nature by the agency of liquids, and not by fusion at a high temperature, Sorby obtained crystalline silica. I use the word crystalline, because it was not distinctly crystallised. His specimens he examined carefully by the microscope, and he was able distinctly to recognise the forms. He first obtained this form by passing chloride of silicon into a tube along with the vapour of water, but he afterwards procured still more distinct crystals by decomposing glass at a high temperature by the agency of water. We may take an ordinary piece of glass and boil water in it for almost any length of time, without appreciably acting upon it; but if we expose ordinary glass to the action of water at a high temperature in a close vessel the result is different, and the glass is rapidly attacked and corroded. By acting upon glass consisting of silica, lime, and potash by water, at a high temperature, he obtained the well-known mineral called Wollastonite, which is a silicate of lime; and he obtained perfectly transparent crystals of quartz, not less than two millimetres in length. Here, then, is a distinct experimental proof of the forma tion of characteristic crystals of quartz, similar to those occurring in nature, by the agency of water, simply at a high temperature, upon silicate of lime and potash, or soda, as the case may be. That is immaterial. It is a