18. d (tang. sec. ) d x (tang. x). (cosec. x) {sec. x = dx x)2 cos. xl tang. x} z 19. d (cot. xi. * ) = d x (cot. x)sin. cos. x {l cot. x * sin. x {l cot. x + (cosec. x)2} dx (cot. x) cot. 20. d (cot. x) = — d x (cot. x) d x (cot. x). = (sec. x) {l cot. x - 1} dx (cot. x)cosec. (cosec. x)2 {cos. x l 25. d (sec. xsin.) = dx (sec. x)si cos. x {l sec. x + (tang.x)2 } 26. d (sec. xco. *) = d x (sec. x)cos. * sin. x {1 7 sec. x} 27. d (sec. ang. ) = d x (sec. x) tang. (sec. x) {l sec. x + (sin. x)2} 28. d (sec. x) cot. = d x (sec. x)eot.x{1 29. d (sec. xsec. x ) = d x (sec. x)". * tang. x sec. x {l sec. x + 1} 30. d (sec. xcosee. =) = d x (sec. x)cose. * cot. x cosec. x { (tang, x)2 - I sec. x} 31. d (cosec. sin. *) = d x (cosec. x)sin. x cos. x {l cosec. x — 1} 32. d (cosec. cos. 3) = d x (cosec. x) = sin. x {l cosec. x + (cot. x)} 33. d (cosec. tang. )= 34, d (cosec. x0t. x ) = +(cos. x)2 } 35. d (cosec. c. ) d x (cosec, x). cosec, x(tang. x) l ARTICLE IX. Experiments on the Composition and Properties of the Naphtha of Amiano. By M. Theodore de Saussure. Read to the Society of Natural Philosophy and Natural History of Geneva.* AFTER ascertaining that alcohol and ether may be represented by olefiant gas and a certain quantity of water, which predominates in the alcohol, I was led to examine whether several other inflammable bodies, of which I shall hereafter give the analysis, might not be subjected to the same law. Öne of the first substances which I examined with this object in view is the naphthat found at Amiano, in the states of Parma, which differs in several remarkable properties from the essential oils. If it were more common, it might advantageously supply the place of oil of turpentine for a variety of purposes. It is more volatile, is at least as good a solvent, has a less tenaceous odour, is not liable to become coloured and thick, to be decomposed by the action of air and light, and is scarcely altered by the action of the most powerful chemical agents, such as the mineral acids and the fixed alkalies. As the properties of this bitumen have not been correctly determined, I make it the subject of the present paper. The knowledge of naphtha is very ancient. Dioscorides and Pliny distinguish by this name a volatile combustible liquid, either white or black, which sometimes issues from the earth, and sometimes collects on the surface of water. They observe that it catches fire at a little distance from an inflamed body; they describe it as found in the same parts of Sicily, Syria, and the Archipelago, where it occurs at present. We do not know the causes that lead to the formation of naphtha in the bosom of the earth. We know only that when asphaltum is decomposed in close vessels by heat, it yields petroleum and naphtha: and that petroleum, which is a heavier and less volatile oil than naphtha, yields it also when thus treated. The asphaltum found in the Val-de-Travers, in Switzerland, appears to have an animal origin. The rock which furnishes it, or which is penetrated with it, is almost entirely composed of shells, and exhibits no trace of vegetables. There is no coal in that country; but we meet with a great deal of sulphate of lime. The mines of asphaltum in the department of the Ain are without any coal in their neighbourhood; but we find animal petrifactions and metalline sulphates. It is probable from this that this kind of bitumen may sometimes owe its origin to the action of sulphuric acid on animal substances. * Translated from the Bibliotheque Universelle, iv. 116, for Feb. 1817. The petroleum of Amiano, which yields abundance of this naphtha when distilled, costs at Genoa only eight centimes the pound, and is employed to light the streets of the city. (Ann. de Chim. tom. xlv.) Rectified naphtha is quite volatile at the ordinary temperature of the atmosphere; but there is reason to suspect that it does not occur naturally in that state. It is usually contaminated with petroleum, which may be separated by repeated distillations, and with which it has been often confounded. The natural naphtha of Amiano appears at its source in its state of impurity as a transparent yellow liquid, with a great degree of fluidity, and having a specific gravity of 0.836. When I drew off by a very slow distillation about a fourth of this substance, I obtained a transparent, colourless liquid, as fluid as alcohol, and having the specific gravity of 0.769 at the temperature of 59°. On distilling this liquid twice more, and retaining only the portions that came over first, it differed very little in its appearance from what I first obtained, and its specific gravity was 0.758 at the temperature of 66°. This density was not diminished by subsequent distillations, even when they were made off a great quantity of muriate of lime. It is to this liquor thus rectified that all the properties which I shall assign to naphtha belong. It was interesting to compare them with the properties of naphthas obtained from a different source; but the naphtha of Amiano is the only one which I could procure in sufficient abundance for a rigid examination. The naphthas which I procured in small quantities by the distillation of the petroleum of Gabian, and of the asphaltum of the department of the Ain, appeared to me to possess, after repeated distillations, the specific gravity of the naphtha of Amiano, the same fluidity, and nearly the same volatility. They had the same action on alcohol, on the mineral acids, and on the alkalies. They did not differ from pure naphtha, except by having a slight shade of yellow. I deprived them of it by distilling them from sulphuric acid; but they became again yellow by exposure to the light; which is not the case with rectified naphtha of Amiano. Notwithstanding this difference, I think that all these naphthas should be considered as identical in their essential principles. Impure naphtha has usually a strong, penetrating, and very lasting odour. That of pure naphtha is weak and fugitive. It is almost without taste. It catches fire at a small distance from an inflamed body, and burns with a white flame mixed with much soot. On paper it forms a stain, which disappears in a few minutes, even in the lowest temperatures. According to most authors, naphtha becomes yellow when exposed to the air and to light; it thickens at the same time, and is converted into petroleum. But such marked results have probably been observed only in naphtha already contaminated with petroleum. In my experiments air and light have had no very sensible action on pure naphtha. I exposed to the sun for 15 days naphtha in contact with 20 times its bulk of air, without observing any change. The experiment was continued for 18 months in a diffuse light, and the volume of the air diminished only one hundredth part. The alteration which it had undergone was scarcely sensible to the eudiometer. The whiteness and specific gravity of the naphtha were not perceptibly altered. The impure naphtha of Amiano deepens in colour when exposed to the light, absorbing oxygen very sensibly. The colourless naphtha obtained by a distillation continued too long, and which has a greater specific gravity than I have indicated for the most complete rectification of this bitumen, becomes yellow in the same manner; but pure naphtha (of the specific gravity 0.758) which I left exposed to the light in phials only half full, has undergone no evident alteration in three years. It is possible, however, that some change may take place hereafter, in consequence of the small absorption of air which I have noticed above. Naphtha may be totally distilled over several times in a moderate heat without undergoing any decomposition. Of the Vapour of Naphtha.-The elasticity of the vapour of naphtha (of the specific gravity 0-7581) is equal to 0.0453 metre (1.78 inch) of mercury at the temperature of 72.5°. Hence it boils at the temperature of 186°. The elasticity of that vapour is deduced from the dilatation which air underwent over mercury when naphtha was let up into it. This air dilated in the ratio of 100 106-67 at the same temperature. This tension, ascertained at the same time in the vacuum of a barometer, was found to amount to 0.0465 metre (1:83 inch). But this last method may be less exact, because naphtha absorbs very quickly a considerable quantity of atmospheric air, which is disengaged in a vacuum, and which cannot be got rid of without putting the liquor again in contact with the external air. The vapour of naphtha has an elastic force four times as great as that of oil of turpentine, which has the greatest elasticity of all the essential oils properly so called. The density of the vapour of naphtha is 2-833, supposing that of common air to be 1. It will be 2.567 if we suppose that of oxygen gas 1. This density was obtained by taking the weight of air saturated with naphtha at the common atmospheric temperature, and following the process for determining the weight of gases. For this operation the air was impregnated with naphtha over mercury in a receiver without lute, and shut by a glass stop-cock, to which was attached a globular vessel exhausted of air, which was to be filled with the air impregnated with naptha. I found that at the temperature of 72.5°, and when the barometer stood at 0.72525 metre (28.55 inches), the weight of common air is to that of air impregnated with naphtha as 1 : 11145. The density and the tension of the vapour of naphtha appear a little less when this liquor swims upon water, and when we employ that liquid instead of mercury to shut the receiver. Air impregnated with the vapour of naphtha has several remarkable properties. This vapour is scarcely absorbed by water. It may be passed a great number of times through that liquid, and even kept over water, without losing its principal characters. The presence of this vapour in some carbureted hydrogen gases may occasion a mistake respecting their composition. Thus by dis tilling over the naked fire different specimens of petroleum, I obtained over water towards the beginning of the process a carbureted hydrogen gas, which, after being washed by a solution of potash, had a specific gravity greater than that of any carbureted hydrogen known. It was 1.1129, supposing that of air to be 1. 100 parts in volume of this gas required for complete combustion 355 of oxygen gas, and formed 220 of carbonic acid gas. It broke in pieces eudiometers of glass which had remained entire under the same circumstances when olefiant gas was detonated in them. I thought at first that I had obtained a new gas; but on observing that naphtha was produced by the distillation of petroleum, and that on the supposition that the new gas was olefiant gas saturated with naphtha, it would have almost the same specific gravity that I found it to have, I concluded that my supposition was well founded.* Common air saturated with the vapour of naphtha (which I shall call naphthated air) burns like carbureted hydrogen gas when placed in contact with a burning body, but cannot be kindled by electricity. This is the case also with naphthated oxygen gas. When a measure of naphthated air is mixed with a measure of hydrogen gas, the mixture cannot be fired by electricity; so that if this test were alone attended to, we might conclude that no oxygen gas was present. It is necessary to add a greater dose of oxygen before combustion will take place. A very small quantity (a 20th, for example) of hydrogen gas, when added to naphthated oxygen, enables the vapour to be kindled by electricity, and the strongest glass eudiometers are broken by the violence of the detonation. If at the common temperature of the air we put a stick of phosphorus into naphthated air standing over water, the oxygen of the air is not absorbed. We must apply a heat sufficient to melt the phosphorus before a diminution of volume takes place. Nitrous gas and the alkaline hydro-sulphurets absorb the whole of the oxygen from naphthated air. We may, therefore, by the difference in the result of the eudiometrical processes with phosphorus at the common temperature and the hydro-sulphurets, judge of the presence of certain emanations in air. I put some peas with water under mercury into a receiver filled with naphthated air. They germinated as readily as in the same quantity of pure atmospherical air; but they vegetated a longer time in this last, and their action on the air was different. In common air the grains replace the oxygen which they absorb by the same volume of carbonic acid gas, and of course do not alter the bulk of their atmosphere. But as soon as they have absorbed all the * The analysis does not agree exactly with that supposition. But the olefiant gas ought to be somewhat modified by the strong heat necessary to distil petroleum. Besides, the analysis can be made only on a small quantity of the gas which I examine, because we are obliged to mix it with six times its volume of oxygen to enable the eudiometer to resist the detonation, |