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gave 0 046 grm. of chloride of platinum and potassium. The coal, therefore, is composed as follows:

[blocks in formation]

The quantity of ironstone consumed by the furnace every twenty-four hours is 33,600 lbs., and that of coal 31,200 lbs., so that the furnace receives every day, in these materials, 271.48 lbs. of potash, corresponding to 377-3 lbs. of cyanide of potassium. Thus these analyses render intelligible the large quantity of potash which we observed in the inferior parts of the furnace.

But we have yet to discuss the most interesting and important question bearing upon the presence of cyanide of potassium, viz. the origin of its cyanogen. We know how easily ammonia, in contact with carbon at high temperatures, is converted into cyanide of ammonium. Hence we should be apt at once to admit that the formation of cyanogen is due to the ammonia so freely evolved from the coal during its distillation; and if this view were correct, the existence of one must arise from the destruction of the other. But when we view more closely the circumstances under which the cyanogen is produced, we are compelled to admit that the ammonia cannot take part in its formation. The hearth, at which the formation of cyanogen takes place, is the deepest and hottest part of the furnace, and it would be absurd to suppose that the coal which reaches this part could contain a trace of ammonia, exposed as it has been for eighty hours to a red heat, and in one part to a temperature sufficient to reduce potash.Hence we are compelled to adopt the only remaining conclusion, that the nitrogen of the air introduced by the blast combines directly with carbon to form cyanogen. This direct formation has been argued for by various chemists, and supported in this country by the experiments of Fownes and Young. But as it has been objected to experiments of this kind, that they were instituted without reference to the ammonia of the air, which is apt to be taken by most substances exposed to it, it is scarcely to be wondered at that the direct generation of ammonia is still doubted by distinguished chemists. We have, therefore, thought it necessary to determine this disputed question by an experiment which seems to banish all sources of error. We have led simultaneously, and under exactly the same conditions, a stream of carbonic acid and another of nitrogen, at a very high temperature, over a mixture of two parts of charcoal from sugar, and one part of chemically pure carbonate of potash, and have subjected the products to careful examination.

The apparatus used by us in these experiments is represented in fig. 9; a is a gasometer, from which a uniform stream of air is made to pass through a bottle filled with sulphuric acid (b), and then through a gun-barrel (cc)

filled with copper turnings. The gun-barrel is kept in a furnace, so that the air passing through it is thoroughly deprived of oxygen, and passes into the gun-barrel (dd) filled with the mixture of charcoal and potash, and heated to a temperature sufficient to reduce potassium. In the same furnace is placed another gun-barrel (ee), filled with the same mixture, and over which is passed a stream of dry carbonic acid from the apparatus fg.

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When both the systems were completely filled, one with nitrogen, and the other with carbonic acid, the streams of gas were allowed to pass slowly over the mixture of potash and charcoal, both the tubes in the same furnace being kept at a temperature sufficient to reduce potassium. The gas passing out of the tube filled with carbonic acid had all the characters of pure carbonic oxide, being transparent, inodorous, and burning with a pale blue flame, without depositing any kind of sublimate. The tube over which nitrogen passed emitted a gas richly laden with a white smoke of cyanide of potassium, which sublimed in such quantity as to stop the conducting tube. When the nitrogen was passed so slowly through the sulphuric acid that the bubbles passed only once in a second, its absorption by the potash was complete, and no gas appeared at the mouth of the gunbarrel; but as soon as the temperature was lowered, so as to be under that necessary for the reduction of potassium, the absorption of nitrogen ceased. The contents of the tube over which carbonic acid had passed were examined after cooling, without the detection of the smallest trace of cyanide of potassium. The mixture treated with nitrogen, on the other hand, dis

solved (with the exception of its charcoal) with a very powerful odor of hydrocyanic acid. The solution exhibited all the reactions of cyanide of potassium, and yielded 6.982 grms. of cyanide of silver, which dissolved (with decomposition) in fuming sulphuric acid, without leaving any residue of chloride of silver after being diluted with water. Hence we cannot for a moment demur to the following conclusion,-That a considerable quantity of cyanide of potassium is formed in iron furnaces immediately above the point where the blast comes in contact with the glowing fuel, and that it owes its formation to a direct union of carbon with potassium and nitrogen of the air.

Our experiments have further shown that cyanide of potassium is volatile at high temperatures, and this property is of much influence in the part which it takes in the reducing process of the furnace. Carried up by the ascending current of gas, the cyanide of potassium, partly in a state of vapor, partly as a solid, reaches the region of the furnace in which the reduction is effected, and here it exerts its well-known reducing power. In consequence of this it is decomposed into nitrogen, carbonic acid, and carbonate of potash, the former of which passes up with the ascending gaseous column to the mouth of the furnace, while the latter, not being volatile, falls back with the other materials in the furnace, to that point where it is again converted into cyanide of potassium, under the influence of the carbon and nitrogen. Hence a large quantity of ore may in this way be reduced in the lower part of the furnace, by comparatively a small quantity of regenerated cyanide of potassium. The importance of this view of the part played by cyanide of potassium, although previously entirely neglected, will be seen when we consider that this powerful reducing agent must accumulate in the furnace to a considerable extent. The region of the furnace where the highest temperature prevails forms a limited space, beyond which the cyanide of potassium cannot extend to the lower parts of the furnace, until its quantity is so much increased, by the potash descending in the materials supplied, that the excess of cyanide of potassium escapes volatilization and reaches the blast, where it is burnt and converted into nitrogen, carbonic acid, and carbonate of potash, the basis of which unites with the slag. We have already shown that the relation of the nitrogen to the oxygen in the gaseous mixture, collected only two and a half feet over the tuyère, is 79-2: 22.8, after deducting a quantity of oxygen corresponding to the hydrogen. If the gas generated at this place contained only the nitrogen and oxygen due to the air, the proportion would be 79-2: 20.8; and hence it follows that the gases at this point must either have obtained oxygen from a source independent of the air, or that a proportion of nitrogen has been abstracted from them. Any one who has had the opportunity of observing the temperature of the furnace at this part, will at once agree with the opinion that the excess of oxygen cannot be derived from the carbonic acid or iron ore. A simple inspection of the materials enables us to reject such an explanation as erroneous, for the fused materials flowing from the furnace do not evolve gas, although they come from a point in the immediate vicinity of that where the oxygen has been taken up.

We must, therefore, admit that this phenomenon is connected with the formation of cyanide of potassium in the furnace. The potash, as it yields

its oxygen to carbon during its conversion to cyanide of potassium, assumes for every volume of oxygen lost by it, two volumes of nitrogen in the form of cyanogen, and consequently the proportion of nitrogen to oxygen is necessarily increased.

Improved Portable Steam Hoisting Machines for Loading and Discharging Cargoes. By A. L. ARCHAMBAULT, Philadelphia.

This useful invention, of which the annexed cut is a representation, was built for Charles Bentric, a stevedore of Philadelphia, who has successfully tested it in discharging the cargoes of the ships Austria, Monongahela, and Hercules.

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The operation of the machine is briefly as follows:-The motion of the engine is communicated to the fly-wheel shaft S, which carries a small pinion gearing into the large wheel f; the winding barrel c, to which the hoisting rope is attached, is locked to the shaft of the wheelf by means of the driving friction coupling a, the latter being thrown into or out of action by the lever d; and the motion of the drum c, when free from the shaft of the wheel f, is controlled by the friction band b, which is tightened or slackened by the brake e.

The machine requires but a single person to keep up steam and attend to the brakes, and is capable of hoisting twelve hogsheads of tobacco from the hold of a vessel and turn them out on the wharf in ten minutes, or can discharge cotton at the rate of three hundred bales per hour. In case the hogshead or other article being raised should strike on the combings of the hatchway, the engineer has only to slacken the brake, and it is lowered, without stopping the motion of the engine, so as to clear the obstruction, and then, by drawing the lever of the brake tight again, the ascending motion is restored. The lowering brake is so arranged that a hogshead of tobacco can be suspended at any point required with the greatest ease. The machine being on wheels, is portable in its character, and can be moved about with a single horse.

A machine of this description should be procured by the stevedores of every sea port, California not excepted.

For the Journal of the Franklin Institute.

An Essay on the Physics of Steam. By THOS. PROSSER, C. E., New York. (Continued from page 136.)

That steam must be either saturated or surcharged will be readily admitted, and therefore, although the fact of its issuing from a high state of elasticity into the atmosphere, at the temperature due to saturated steam under that pressure, does not, per se, prove it to be surcharged, yet, taken in connexion with another fact, viz. that such steam does not scald the hand, affords certain proof that there is some physical difference between expanded steam and steam which has not been expanded; and as only two states of existence are known-saturated and surcharged-it necessarily follows that, on the score of probabilities, we are entirely justified in assuming that it is surcharged, in the absence of any reliable direct experiments on the subject.

It has been mentioned before that low pressure steam is a conductor of electricity, and I may now add that high pressure steam is a non-conductor,* but what bearing this has on the cause of expanded steam being surcharged it is difficult to say, in the present state of our knowledge of that most mysterious agent; whether, as the cause, in consequence of the electricity being converted into heat, which Pelsier has shown to be possible,† or simply as another effect of the same cause.

The electricity of effluent steam was first noticed by an engine-man at Seghill, about six miles from Newcastle, England. The first observations on the electricity of a jet of steam, while issuing from a boiler, is contained in a letter addressed by H. G. Armstrong, Esq., to Professor Faraday, and published in the 17th volume of the London and Edinburgh Magazine, Oct. 14, 1840. There are also some very interesting remarks on the same subject in this Journal, 3d series, Vol. I, p. 123. Evaporation is undoubtedly the great source of electricity in the atmosphere, as well as in the boilers of steam engines, and there appears nothing irrational or unphiloJournal of the Franklin Institute, 3d series, Vol. 1, p. 123.

†Noad's Lectures on Electricity, p. 250, ¶ 408.

Noad's Lectures on Electricity, p. 252.

VOL. XVIII.-THIRD SERIES.-No. 3.-SEPTEMBER, 1849.

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