Though great advancement has been made within these few years in chemical pharmacy, by the labours of the very ingenious Dr. Lewis, and some other writers on chemistry and the materia medica, there is still a wide field left for improvement. It is to be wished that Apothecaries, to whose province researches of this kind more peculiarly belong, and many of whom are well qualified by a liberal education to pursue them with advantage, would give their attention to these material interests of the art: for while the several professors of medicine and of surgery, are most laudably and assiduously employed in adding to the enlargement of these sciences, why should the sons of pharmacy remain supinely inactive, and leave every thing towards the improvement of their profession to be performed by the members of the elder branch of physic, instead of contributing _their_ share to its support? as if tacitly acknowledging themselves unequal to the task, and thereby incurring the too general, though unmerited, imputation of want of knowledge and skill in their department. The first part of the ensuing Treatise, which relates _an improved method of preparing Magnesia Alba_, has been communicated to the College of Physicians; and that learned body have done the author the honour to insert it in the second volume of their TRANSACTIONS. It is here reprinted as a proper introduction to the subsequent pages. The calcination of Magnesia is not a new process[a]; but, as in this state it is a medicine not much introduced into practice, perhaps a few hints may be suggested, in regard to its medicinal and pharmaceutical properties, which are not generally known; and it is hoped that some useful information may be communicated relative to the various action of absorbent medicines on the bile. [a] The German and Italian chemists formerly prepared Magnesia by evaporating the mother of nitre, and then calcining the residuum; but, Hoffman having discovered the method of precipitating it from the bittern remaining after the crystallization of sea salt, the calcination was disused, as tedious and unnecessary. In the succeeding chapters, it is attempted to determine how far, and in what proportion, lime promotes the solution of vegetable astringents, and other drugs in water; and whether the action of antiseptic medicines, thus dissolved, be in any degree impaired or increased by this mode of obtaining tinctures from them. In endeavouring to contribute to the determination of the question, whether fixed air has the power of restoring sweetness to putrid substances, the Author may at first sight appear to have transgressed his proper limits; but, as fixed air, if possessed of this property, is likely to be a valuable acquisition to the materia medica, he flatters himself he shall incur no censure by the attempt. THE CONTENTS. CHAP. I. Page