Prof. Seely. The more I think of the matter, the more am I amazed at what chemistry enables us to do. If you bring us a candle we do not need to light it in order to tell you what it is worth. A hydrocarbon, to give the most light, should have the hydrogen slightly in excess. If the carbon is in excess there will be smoke. It has been frequently talked over here and is now generally understood, that the light comes from the carbon, heated to a white heat. It may, perhaps, be more easily comprehended if it is presented thus: Suppose we had a quantity of carbon, in the form of coal for instance, which we wished to burn in the way to get the most light from it possible, how should we wish to arrange it? We should want it in a thin stratum so as to expose a large surface, and we should wish to keep it hot as long as possible before it was burned, for as soon as combustion took place it would be converted into invisible gas, and would cease to give out light. Finally, we should want it in small pieces, so that the light might be soft to the eye. We have no means of arranging carbon in this way. But nature makes the arrangement beautifully. By combining atoms of carbon with atoms of hydrogen, which separate at a lower temperature than carbon will burn at, the carbon is heated before it is burned; and as the hydrogen occupies much more space than the carbon, the carbon atoms are enveloped by the hydrogen, and thus kept from burning until the hydrogen is consumed. The burning, too, is confined to an excedingly thin film on the outside of the blaze, and thus the illuminating power of the carbon is fully utilized. Mr. Chairman, we have had a very grand exhibition this afternoon of combustion of illuminating materials. Some 18,000 barrels of petroleum oil have been burning in Williamsburgh, and if it had occurred in the night, I have.no doubt that we should have had the finest illumination that has ever taken place. As it was, the smoke, as seen from the lower part of the city, made the most magnificent spectacle that I have ever seen. The Express says that the fire originated from an explosion which occurred in one of the vessels which were lying at the wharf discharging petroleum. The account says that after the explosion in the vessel, a barrel on the wharf exploded, and the word explosion occurs half a dozen times in the account. I have no doubt that we shall have a discussion in the papers whether petrolium will explode. Some people seem to think that if you touch a match to a cask of petroleum it will go off like gunpowder, and' there is quite a common notion that rock oil will explode. It will not do it. The explosion occurs in this wise: Petroleum has the property above all liquids of passing through capillary tubes. If you put it into a wooden barrel it will go right through the staves, and the barrel will be greasy directly on the outside. The most volatile portion passes through the most readily, and when this, in the form of vapor, is mingled with the atmosphere in a confined place, as the hold of a vessel, an explosive mixture is formed. Petroleum is not explosive; but a mixture of the vapor of petroleum with atmospheric air is explosive; and this mixture can be formed only in a close chamber. The question is similar to the famous one, "Will saltpeter explode ?" and the answer is analogous. Saltpeter alone will not explode, any more than a stick of wood or a brick; but when saltpeter is mixed with any combustible, the mixture is explosive. Mr. Churchill. I understood Prof. Seely to say that many of the hydrocarbons in burning would necessarily smoke. I made a great many experiments with lamps while on the committee last winter, and I have continued them since, and I think there is no fat that cannot be burned without smoke in a still atmosphere, if the lamp is not moved about. Prof. Seely.-You must have misunderstood me; I agree with you entirely. The Chairman.-There are a few minutes left; will any one make any remarks or ask any questions? I will inform the society that I shall leave the country in a few days for Europe, and I shall regard myself as a sort of traveling agent of the society at my own expense. I shall try to learn everything of interest to this Association, especially the working of similar societies, which I shall communicate to you on my return, as occasion may offer. Since I have had the honor to preside over your meetings, I have become exceedingly attached to the work. I shall be absent five months, and perhaps you ought to take some steps to provide a presiding officer during my absence. Mr. Dibben. Mr. Chairman, during the summer months it has been our practice to discontinue our meetings, and in the few meetings that we shall hold during your absence, we can choose a chairman pro tem. On motion of Mr. Fisher, the thanks of the society were voted to the Chairman for the firm and satisfactory manner in which he had presided over the meetings. The subject of "Superheated Steam" was chosen for the next meeting, and the society adjourned for two weeks. JOHN K. FISHER, Secretary pro tem. AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION, June 19, 1862. } Dr. R. P. STEVENS in the chair. PREMIUMS OF THE AMERICAN INSTITUTE FOR 1862. Mr. Fisher, Secretary pro tem., read a communication from the board of managers of the American Institute, stating that they had delegated the award of premiums to be given by the Institute this year to the Polytechnic Association and the Farmers' Club. A list of the premiums, and the subjects for which they were offered, are as follows: For the best machinery for spinning and weaving flax.......Gold Medal. For the best lifting and force pump-by hand power........Silver Medal. For the best novelty in building materials, and machinery for preparing the same... .Silver Medal. ......Silver Medal. For the best novelty of practical value extracted or manu- Gold Medal. For the best novelty in the construction of railroads........Silver Medal. For the best novelty in warming and ventilating buildings, having especial regard to health, safety and economy.....Silver Medal. For the best essay on the measure of power.... ...Silver Medal. For the best original researches or monographs on any subject pertaining to the science of chemistry, or mechanics, or their practical applications... ....Gold Medal. For the best samples of American manufactured flax fabrics, with the cost of manufacture....... ...Silver Medal. For a cheap and easy test of the true value of lubricating oils, Silver Medal. ..Silver Medal. ..Silver Medal. ..Silver Medal. ..Silver Medal. For the best lamp to burn kerosene oil, producing perfect combustion... ..Silver Medal. ..Silver Medal. ...Silver Medal. For the best plan for burning kerosene oil for heating purposes Three discretionary premiums (gold or silver medals)-to be determined by the board of managers. Mr. Dibben.-I see Mr. Johnson here, who is a member of the board of managers, and I would like to ask what steps are to be taken to inform those who would be likely to compete for them, in regard to the subjects for which premiums are offered by the Institute? Mr. Johnson. The managers will furnish the Association with circulars for distribution. Mr. Rowell exhibited an instrument for showing the temperature at which coal oil ignites. Mr. G. Tagliabue is the inventor and maker. In Europe no oil is allowed to be sold, for illuminating purposes, which ignites at less than 115o. Prof. Seely. I think the instrument good, but not all that is needed. If oil is shaken, even at 90°, we may have an explosive mixture. This is the best instrument I have seen. Mr. Johnson said he had found no difficulty in setting fire to all the oils he had tried. Mr. Rowell.—I have tried many times and found that the vapor of oil would not ignite below 110° in this instrument. It is to test the comparative explosibility of oils, to show which are comparatively safe. Mr. Seely. Where oil is homogeneous the hydrometer is a good test, but, since the manufacturers have mixed oils, it is not reliable. Dr. Stevens. I think it important to have an instrument to test all oils offered in market, whether on store or for sale. Lives should not be jeopardized from mere ignorance, carelessness, or sheer cupidity. I have known a valuable life lost, the head of a family, dependent upon him for support, by drawing from a barrel of explosive compound sold from this city. When lives are lost from new causes, there is always a season of great excitement; there has recently been an increase of this from a few cases of death from explosive vapor arising from petroleum oils, while the far greater number of deaths arising from the use of burning fluid was forgotten. As to the temperature at which an explosive mixture will take place, the compound of air and vapor will take place at low temperatures, when the vapor is derived fresh from the bowels of the earth. At the burning springs of New York and Ohio, this mixture takes place at the common temperature of the air; at all seasons when the springs flow, spring, autumn, or summer, beautiful pyrotechnic exhibitions are then gotten up extemporaneously. The subject of the evening, "Superheated Steam," being called up, Mr. Babcock said: I know an instance in which superheated steam had been in use six years, and saved 25 per cent., and the apparatus cost nothing for repairs. It is automatic. The invention is by Wilcox Stillman. The steam passes through a set of tubes; the smoke and heat cross these tubes several times; between the fire box and chimney is a damper to regulate the quantity of smoke and heat which pass over the tubes; the pressure is 50 lbs., condensing 100°; temperature of steam 450°. Prof. Seely. The heat used in superheating is commonly waste heat, or the heat going up the flues, in the products of combustion. Such heat makes no extra cost, and all that gets into the steam shows itself in mechanical force. The heat, however, which gets into the water in the boiler is not all available in work; until the water reaches the boiling point, the expansion, although of great force, is of such narrow limits that we do not use it. To raise water from 0° to 212°, 20 per cent. as much heat is required as to raise it then into steam; and this 20 per cent. gives no motion to the engine. But the value of superheating is more plainly shown in another direc tion, and by using figures. In order to be easily understood, I use only round numbers, but numbers which are very near the exact truth: 1 lb. of water at 212 is converted into 1,700 volumes of steam, by 1,000 units of heat. The 1,700 volumes may be taken as the measure of the available mechanical force; the 1,000 units of heat are worth 1,700. Now, if these 1,700 volumes of steam at 212° be raised 500° higher, or to 712o, the bulk will be doubled; for the heat put into the steam we have another 1,700 volumes; or, in other words, the heat used upon the steam has given us the same value as the heat used upon the water. How much heat is there required to raise 1 lb. of steam 500°? The specific heat of water is 1, and the specific heat of steam .5, or a unit of heat will raise 1 lb. of water 19, and 1 lb. of steam 2°. But in our case, suppose the steam was raised 500°, and now it is evident at a cost of 250 units of heat. The 250 units of heat used in superheating steam have done the work of 1,000 units used upon water; heat goes four times farther on steam than on water. If waste heat is used for superheating the steam to 712°, we double our power without increased cost for fuel; or, if the heat costs at the same rate as when used in water, we double power at an additional outlay of 25 per cent. In the first case, we realize a total gain of 50 per cent., and in the second, of 37 per cent. But, unfortunately, it is not yet practicable to use steam at a temperature so high as 712°; the materials we use about our engines will not endure it; we can, however, practically use steam at about 400°, and thus realize an economy as high as 25 per cent. Superheated steam is now much used in chemical operations, as a convenient means of heating, and to effect certain decompositions. Superheated steam upon iron, at a red heat, gives its oxygen to the iron and its hydrogen escapes; upon carbon, at a white heat, its oxygen unites with the carbon to form carbonic oxyd and carbonic acid, and the hydrogen is set free; upon metallic sulphides, the hydrogen unites with the sulphur to form sulphide of hydrogen, and the oxygen with the metal; upon oils, when the fat acid is separated from the glycerine, &c., &c. Mr. Rowell. I hold in my hand a table of the observations made at one of the series of experiments which were tried at the Metropolitan mills in this city, in 1860, to test the value of superheating steam and of working steam expansively. These experiments were made under the direction of B. F. Isherwood, now engineer-in-chief of the United States Navy, at a cost of about $5,000, which was paid by Mr. George Hecker. They were commenced on the 1st of February, and finished on the 1st of November. An engine was constructed expressly for the purpose, and it was the first time in the history of the steam engine, in which an engine was made for the single purpose of testing questions in regard to its operation. The fuel and water of condensation were carefully weighed, and the temperature and pressure of the steam in all parts of the apparatus, as well as the temperature of the room, the barometric pressure, the temperature of the feed water, and, in short, all circumstances that could affect the result, were carefully observed and recorded every hour. It was the most valuable, as well as the most costly, series of experiments that have ever been made in regard to the practical working of steam. The plan of superheating was to surround the cylinder with a steam jacket, and then throttle the steam in the cylinder, so as to reduce its pressure without diminishing its temperature. It was found that there was no marked economy in superheating more than 5o. At this extent of superheating, the economy was 54 per cent.; that is to say, 46 pounds of coal, with this method of superheating, did as much work as 100 pounds of coal, with steam used in the ordinary way. Mr. Dibben.-I introduced this question with an idea that the facts brought out would show that the prejudice against superheated steam is not well founded, and the discussion has fully sustained my opinion. The statement of Mr. Babcock shows that if a superheater is properly constructed, there is no burning out of the tubes, about which we have heard so much, and the working of Ericsson's air engines proves conclusively that lubri cating materials will bear a temperature of 450° without being decomposed. |