consist of an alkaline earth, which is soluble by itself in water; but which, when combined with a large quantity of fixed-air, becomes insoluble; losing the properties of quick-lime, and assuming the appearance those earths naturally have, when not reduced to a calcareous state.
Dr. Black observed the same phenomenon in white magnesia, and in alkalis both fixed and volatile. Their effervescence with acids, and their mildness, depend on the fixed-air which these bodies contain; because alkalis and calcareous earths become in a high degree caustic, when divested of that gas. He farther remarked, that fixed-air had different degrees of affinity with various substances; being stronger with calcareous earth than with fixed alkali; with the latter than with magnesia; and with this than with volatile alkali.
This new gas was introduced into the catalogue of medicines, by its strongly antiseptic properties: it cannot, however, on account of its fatal effects, be inspired in large quantities, though in small portions it may be inhaled without danger.
Dr. Percival first administered it on a large scale, and directed his patients, in more than thirty cases of pulmonary consumption, to inspire the steam of effervescing mixtures of chalk and vinegar through the spout of a coffee-pot. By this treatment, the hectic fever was, in several cases, considerably abated, and the matter expectorated became less offensive, and better digested. Although Dr. Percival was not so fortunate as to effect a cure in any one instance, yet the late Dr. Withering met with better success; as one of three patients was thus restored to perfect health; another received great benefit, and was much relieved; and the third was kept alive by inhaling this gas for more than two months. Fixed-air, however, can only be employed with advantage in those stages of pulmonary consumption, when a purulent expectoration, or a rupture and discharge of an abscess in the lungs, have taken place: in such cases, this remedy affords a powerful palliative.
Farther, it is equally useful when applied to foul ulcers; and instances have occurred, in which the sanies, or corrupt matter issuing from cancers, has been sweetened, the pain alleviated, and a better suppuration produced, even after the carrot-poultice had failed. But, though fixed-air evidently checks the progress of a cancer, there is reason to apprehend that it never will effect a cure.
Considerable benefit has also been received in ulcerated sore-throats, from inhaling the vapours arising from effervescing mixtures. This remedy ought, however, by no means to exclude the use of other antiseptic applications.
In that dreadful disorder, the malignant fever, wines strongly impregnated with fixed-air may be administered, with a view to check the septic ferment, and to neutralize the putrid matter in the stomach and intestines. If the patient's common drink were thus prepared, it might be attended with beneficial effects.—As the latter stages of malignant fevers are generally accompanied with putrid diarrhœas, this evacuation ought not to be restrained by the use of astringent medicines; because the retention of putrid matter in the body will aggravate the delirium, and increase the vehemence of the fever. And
