PART I.

INTRODUCTORY.

PRELIMINARY REMARKS.

DEFINITION, GENERAL PRINCIPLES, OBJECTS, UTILITY, AND IMPORTANCE OF QUALITATIVE CHEMICAL ANALYSIS, THE CONDITIONS AND REQUIREMENTS FOR A SUCCESSFUL STUDY OF THAT SCIENCE.

CHEMISTRY is the science which treats of the various materials entering into the structure of the earth, their composition and decomposition, their mutual relations and deportment in general. A special branch of this science is designated Analytical Chemistry, inasmuch as it pursues a distinct and definite object-viz., the analysis of compound bodies, and the examination of their component elements. Analytical chemistry, again, is subdivided into two branches-viz., qualitative analysis, which simply studies the nature and properties of the component parts of bodies; and quantitative analysis, which ascertains the quantity of every individual element present. The office of qualitative analysis, therefore, is to exhibit the constituent parts of a substance of unknown composition in forms of known composition, from which the constitution of the body examined, and the presence of its several component elements may be positively inferred. The efficiency of its method depends upon two conditions-viz., it must attain the object in view with unerring certainty, and in the most expeditious manner. object of quantitative analysis, on the other hand, is to exhibit the elements revealed by the qualitative investigation in forms which will permit the most accurate estimate of their weight, or to effect by other means the determination of their quantity.

The

These different ends are, of course, attained respectively by very different ways and means. The study of qualitative analysis must, therefore, be pursued separately from that of quantitative analysis, and must naturally precede it.

Having thus generally defined the meaning and scope of qualitative analysis, we have now still to consider, in the first place, the preliminary information required to qualify students for a successful cultivation of this branch of science, the rank which it holds in the domain of chemistry, the bodies that fall within the sphere of its operations, and its utility and importance; and, in the second place, the principal parts into which its study is divided.

It is, above all, absolutely indispensable for a successful pursuit of qualitative investigations, that the student should possess some knowledge of the chemical elements, and of their most important combinations, as well as of the principles of chemistry in general; and that he should combine with this knowledge some readiness in the apprehension of chemical processes. The practical part of this science demands, moreover, strict order, great neatness, and a certain skill in manipulation. If the student joins to these qualifications the habit of invariably ascribing the failures with which he may happen to meet, to some error or defect in his operations, or, in other words, to the absence of some condition or other indispensable to the success of the experiment-and a firm reliance on the immutability of the laws of nature cannot fail to create this habit -he possesses every requisite to render his study of analytical chemistry successful.

Now, although chemical analysis is based on general chemistry, and cannot be cultivated without some previous knowledge of the latter, yet, on the other hand, we have to look upon it as one of the main pillars upon which the entire structure of the science rests; since it is of almost equal importance for all branches of theoretical as well as of practical chemistry; and I need not expatiate here on the advantages which the physician, the pharmaceutist, the mineralogist, the rational farmer, the manufacturer, the artisan, and many others derive from it.

This consideration would surely in itself be sufficient reason to recommend a thorough and diligent study of this branch of science, even if its cultivation lacked those attractions which yet it unquestionably possesses for every one who devotes himself zealously and ardently to it. The human mind is constantly striving for the attainment of truth; it delights in the solution of problems; and where do we meet with a greater variety of them, more or less difficult of solution, than in the province of chemistry? but as a problem to which, after long pondering, we fail to discover the key, wearies and discourages the mind: so, in like manner, do chemical investigations, if the object in view is not attained—if the results do not bear the stamp of truth, of unerring certainty. A half-knowledge is therefore, as indeed in every department of science, but more especially here, to be considered worse than no knowledge at all; and a mere superficial cultivation of chemical analysis is consequently to be particularly guarded against.

A qualitative investigation may be made with a twofold view-viz., either, 1st, to prove that a certain body is or is not contained in a substance, e.g. lead in wine; or, 2nd, to ascertain all the constituents of a chemical compound or mixture. Any substance whatever may of course become the object of a chemical analysis.

In the present work, however, we purpose to confine ourselves to those elements and compounds which are more generally employed in pharmacy, in the arts and manufactures, and in agriculture.

The study of qualitative analysis is most properly divided into four principal parts-viz.,

1. CHEMICAL OPERATIONS.

2. REAGENTS AND THEIR USES.

3. DEPORTMENT OF THE VARIOUS BODIES WITH REAGENTS.

4. SYSTEMATIC COURSE OF QUALITATIVE ANALYSIS.

It will now be readily understood that the pursuit of chemical