ORGANIC ANALYSIS is the generic term for a great number of chemical and physical operations, that have for their object the ascer taining of the composition and constitution of all matter that has been formed under the influences existing in animal and vegetable life. It also, of course, includes the similar examination of all derivatives and artificial imitations of the matter referred to.
In illustration of the above definition of organic analysis, let us suppose that we have for examination some well-known fruit, such as a pear. By processes presently to be described, we separate and isolate from it the matter or matters that appeal to the eye, in other words the colouring agent; similarly we obtain the odoriferous principle ; then a matter that has no odour, but a distinct and well-defined taste ; next we chemically dissect out the framework or skeleton ; and finally tune our attention to the great mass of substance with which the framework is filled in. Operations are next undertaken by whjeh we assure ourselves that the bodies thus separated are neither more nor less than what we suspect them to be ; uniformity is hero the great character istic. Solid or liquid, the body in question must have a constant specific gravity ; taste, odour, touch, must be unvaried ; to tho eye, alone or aided by the microscope, the appearance of each observable particle must be identical ; if a fusible solid, it must have a constant melting point ; if a volatile liquid, its boiling point must be unvarying. .The next series of operations acquaints us with the number of elementary substances contained in each body under examination, as well as with the exact per tentage amounts of those elements. Having now, to a certain extent, a knowledge of the composition of the bodies, we arrive at their probable constitution by a process of analogical reasoning; and this is confirmed or disproved by severally subjecting them to powerful chemical reagents. Possibly the latter cause the substances to be split into two or three bodies of more simple constitution ; if so, they each must be passed through the prescribed ordeal. The odoriferous
principle, for instance, of the pear has been isolated in a state of purity, and has been found to contain certain constant centesimal amounts of three elements ; but on farther chemical examination it breaks up into two compounds, each of which however is found to possess uniform properties, and to have a constant centesimal composition. And now, having individnalised and given character to each of the bodies under examination, WO probably recognise them as old acquaintances, or possibly take to ourselves the merit of having discovered new ones. Our pear would yield us such bodies as water, starch, lignin, sugar, ; the flavouring principle, or essence of pears as we might call it, being found by the latter part of the examination to be a compound of acetic acid and oxide of amyl, or shortly the acetate of ainyL Several of the bodies enumerated may be artificially produced, their identity with the natural products being established by tho similarity in their physical and chemical characters, especially as evidenced by their per centago composition.
From what has already been stated, it will be observed that organic analysis is either proximate or ultimate. The appearance and behaviour of bodies when acted upon by various reagents or tests may, when viewed by an experienced eye, be sufficient to establish their individu ality, and their presence and even amount, in the matter originally operated on, may thus be satisfactorily determined : such is proximate organic analysis. But perhaps the bodies in question have no well marked properties, or are possessed of characteristics not before observed in any known substance ; in either case the number of their elementary constituents must be discovered, and the amount of each element ascertained; and such is ultimate organic analysis. Ultimate analysis also forms, as it were, the court of appeal from the decisions arrived at in proximate analysis.