This gas is above twice as heavy as at mospheric air : it kills animals very speedily,and extinguishes burning bodies. From this latter property it has been re commended, when a chimney is on fire, to throw a spoonful or two of flowers of sulphur into the grate. It whitens and gives lustre to silk, and is useful in bleaching woollens. Fresh prepared muriate of tin decomposes it, sulphur being deposited, and the mitriate oxy genized. Mr. Northmore has condens ed it by pressure: and Mange did the same, with the addition of artificial cold. According to Dr. Thompson, it consists of sulphur sixty-eight parts, oxygen thir ty-two.
One hundred grains of water take up 5 grains of this gas, or 25 parts by mea sure; or, according to Dr. Thomson, 8.2 grains, equal to 33 times its volume. The solution has a pungent disagreeable odour, and an acid taste. It reddens some of the vegetable colours, such as that of litmus, or red cabbage ; there are others, however, the colour of which it destroys, as that of the red rose. The effect of the gas upon these colours is similar.
The saturated solution allows the gas to escape at a very moderate heat, and by boiling, the greater part is expel-led, though the liquor remains acid, appa rently from the presence of sulphuric acid. It is singular that it is not expelled by freezing, but still remains combined with the ice, and renders it so heavy that it sinks in water. This act shows that that this has, comparatively with others, little tendency to pass into the aeriform state. The freezing of the solution takes place at a few degrees below 32.
When two parts of the gas are mix ed with one part of oxygen gas, if the mixture is kept over mercury, they do not act on each other. But if a small portion
of water is introduced, they gradually combine and form sulphuric acid, a fact explained by Mr. Murray, on the suppo sition that the water exerts a strong dis posing affinity to this acid, or, to speak more intelligibly, according to the expla nation of disposing affinity given under our article CHEMISTRY, the water at tracts the sulphurous gas, and, by de priving it of its state of elastic fluidity, renders it capable of more readily uniting with the oxygen, which is also effected by a like action of the water ; and as these combine into sulphuric acid, which is more soluble than the sulphurous, the process is still more facilitated, and goes on progressively until the effect is com pleted. By passing s mixture of oxygen gas and sulphurous acid gas through a tube heated to redness, they instantly combine, and sulphuric acid is formed.
This acid combines with facility with the alkalies, forming salts denominated sulphites, which differ considerably from the salts formed by the sulphuric acid. Their taste is sulphurous ; they are de composed by a high temperature, their acid being either expelled, or a portion of sulphur being driven off, in which case they become sulphates ; they are also de composed by the greater part of the acids, and then the sulphurous acid is disengaged with effervescence. The al kaline sulphites are more soluble than the sulphates in water, the earthy sul phates less so. All these salts are con verted into sulphates by exposure to the atmospheric air, or by the action of any snbstance capable of affording them oxy gen. They suffer this change, for exam ple, by deflagration with nitre. See SUL PHUROUS ACID.