This explanation is founded on the sup position, that the sulphuric acid decomposed in the process by which ether is formed. But a few years ago it was affirmed by Fourcroy and Vauquelin, from a series of experiments which they undertook to elucidate this subject, that such a decomposition of the acid is not at all necessary to its formation : that al though it may take place to a certain ex tent towards the end of the process, when the liquor is loaded with carbon; there is no indication of it in the first stage, during which, principally, the ether is ffirmed : no sulphurous acid gas is discharged, and if the process be stopped at the end of this stage, the re maining acid, they found, is capable of saturating the same quantity of alkali as before its mixture with the alcohol. (" Nicholson's Journal," 4to. vol. 1. p. 385.) These chemists gave, therefore, a dif ferent view of this subject, which they applied even to the action of this acid on vegetable matter in general. They suppose that the sulphuric acid suffers no decomposition, and that it acts no other part than causing, by the exertion of a disposing affinity, the decomposition of the alcohol. By this affinity, it dis poses part of the hydrogen and of the oxygen of the alcohol to combine and form water : the balance of attractions being thus subverted, a quantity of car bon is separated, and the remaining car bon, hydrogen, and oxygen, combine and form ether.
This theory, however, advanced by these chemists, is not perhaps perfectly established. Though they affirm, that the acid remaining after the formation of ether saturates as much alkali, as it would do previous to its mixture with the alcohol, the experiment by which this is supposed to be established is not altogether without fallacy. During the formation of ether, there is always, also, a formation from the elements of the al cohol, of some of the vegetable acids, particularly of the acetous and oxalic. The oxalic, it has been ascertained by the observation of Cadet, is formed co piously even without heat, merely by allowing the mixture of acid and alcohol to remain at rest for some time. These will contribute to the saturation of the alkali ; so that if none of the sulphuric acid were decomposed, more alkali ought in reality to be saturated by it after, than before, its mixture with the alcohol.
There are also some facts which ap pear to prove the necessity of the pre sence of some substance that can part with its oxygen, for the production of ether. Thus, ether cannot be formed from the muriatic 'acid, but it can with facility from the oxymuriatie; it is like wise formed with great rapidity by the nitric acid; neither of which can exert a strong disposing affinity to water, though both very readily part with their oxygen.
Whatever opinion, however, may be formed as to the manner in which the changes that take place during the for mation of ether are produced, the na ture of the changes themselves seems sufficiently well ascertained. It is proved, that a quantity of the hydrogen of the alcohol is expended in the formation of water, as the remaining acid is always in a diluted state: a still larger quantity of carbon is also separated, and is mechani cally diffused through the liquor. The
ether, therefore, which is the only other product of the operation, is to be consi dered as a compound of hydrogen and carbon, and perhaps oxygen ; differing from alcohol, in containing a much larger quantity of hydrogen, proportioned to its carbon ; and to this predominance of hydrogen its great levity and volatility are owing. This conclusion is confirm ed, by its analysis by combustion, the products of which are water and car bonic acid ; the former being• de'-ived from the combination of its hydrogen with the oxygen of the air, the latter from the same combination of its carbon. Mr. Cruikshank found, that the vapour of ether requires about seven times its volume of oxygen to saturate it in com bustion ; the products being water and carbonic acid gas, the latter amounting to 4.6 parts by measure. From this result, compared with a similar experiment on alcohol, he inferred, that the proportion of carbon to hydrogen in the ether Is as 5 to 1 nearly, while in alcohol it is as 8 or 9 to 1. (" Nicholson's Journal," 4to. vol. v. p. 205.) Besides ether, there are some other products formed during the action of sulphuric acid upon alcohol. Towards the end of the process an oily-like mat ter distils over, which has been named Sweet Oil of Wine. This can be ob tained separate, by changing the re ceiver : it is unctuous, thick, and less volatile than the ether, but is soluble both in it and in alcohol. It is obtained, likewise, by distilling sulphuric ether from a fresh quantity of acid. Chemists are not agreed respecting its nature Fourcroy and Vauquelin consider it as si milar to ether, and that it differs from that fluid, principally, in containing a larger proportion of carbon, which gives to it more density and less volatility. Other chemists, particularly Higgins, have af firmed, that it is a compound of ether and sulphurous acid, and that by the ad dition of an alkali, which combines with the acid, a quantity of ether may be ob tained from it. It does not appear, how ever, that this combination can be formed directly, or that ether can combine with a large quantity of sulphurous acid, so as to assume the properties of oil of wine ; and though this substance may contain a ,portion of this acid, it is not improbable that it also differs from ether in its ulti mate composition. At the same time that the oil of wine is disengaged, there is formed a quantity of olefiant gas, which passes of It was in this process, indeed, that the production of this gas was first observed ; and the action of sulphuric acid on alcohol still affords us the best method of obtaining it pure. The same gas is produced, by passing the vapour of ether through an ignited earthen tube ; but when a glass tube is used, a different variety of carburetted hydrogen is ob tained.