Organic analysis and inorganic analysis are conventional divisions of chemical analysis. Each is subdivided into proximate and ultimate, and either one of the four classes is qualitative or quantitative in the sense of those words already alluded to under CHEMICAL ANALYSIS. The line of demarcation that separates these divisions is nut very sharp ; many bodies being found in animals and vegetables in a state not dis tinguishable from that in which they exist in the inorganic kingdom ; such, of course, demand inorganic analytical treatment. Other bodies require modifications of organic or inorganic analysis, according to the nature of the substances with which they are associated, and from which they are to be isolated. The broad principles, however, of in organic and organic analysis are pretty well defined, and the difference between them easy of practical recognition. While, on the one hand, inorganic analysis comprehends the manipulatory processes connected with the examination of metals and their salts : organic analysis, on the other hand, includes only operations which aid in discovering and investigating the apparently innumerable series of compounds formed by the union, in various ways, of the four elements—carbon, oxygen, hydrogen, and nitrogen.
Proximate Organic Analysis.
This is by far the more difficult branch of organic analysis. An animal or vegetable substance usually contains a much greater number of proximate principles than the most complex mineral ; these principles have been built up by the agency of that mysterious aggregation of influences sometimes, though very unphilosophically, termed vital force ; and, inasmuch as organic matter is necessarily only examined after those influences have been withdrawn, it follows that there is a constant tendency, as in all dead animal and vegetable matter, to return to its original more simple and stable condition. In addition to this source of complication, the bodies in question being held together by such weak affinities, are not only more readily acted upon and altered by the agents employed by the chemist to separate them, but very frequently act upon each other ; so that, indeed, the perfect proximate analysis of organic matter is, in the present state of our knowledge, an impossibility; and the various published processes, professing to give a means of arriving at that desirable end, must be looked upon as being merely provisional. We are, however, able to isolate very many proximate principles, and it is quite admissible to include in an analysis such substances as "extractive matter," "balsamic matter," "resinous matter," " ethereal, alcoholic, aqueous, or alkaline extractive," &c., provided always that it be remembered that such names are only pro visional, and that in future times, as in times gone by, an increasing number of definite principles will probably crop out from such collective substances, and finally their names be altogether expunged from proximate organic analysis.
We are indebted to Rochleder for the latest improvements in this department of chemistry. The process may shortly be stated as follows. (For further details see ' Pharmaceutical Journal ' for 1860.) The organic matter is first mechanically disintegrated. The more points of contact presented by a solid to the. solvent action of a liquid, the better it is ; so that comminution cannot well be carried too far. Often a certain degree of moisture renders the material tenacious and elastic, so that it is difficult of pulverisation ; in that case a careful drying suffices to bring it into a pulverisable condition. Sometimes oily bodies cause the same kind of tenacity, and then expression of the cold or slightly warmed material will expedite matters. In other eases appropriate solvents may be used for the removal of bodies causing tenacity, and disintegration thus facilitated. If pulverisation cannot be accomplished by stamping or rubbing, recourse may be had to rasping, slicing, &c. Obviously much will depend upon the charac teristic properties of the substance operated upon, so that no general rule can be laid down ; at the same time, however, the above hints may give an ides of the methods to be adopted.
The material in a fine state of division is now divided into several portions, and each treated with a solvent, in order to obtain a number of extracts, which are to be submitted to farther examination.
One portion is boiled with water in a distillatory apparatus, by which a decoction and a distillate are obtained ; the former will contain non volatile constituents soluble in water, the latter volatile matters only. Another portion is treated with cold water, in order to dissolve out such matters as would be coagulated by the hot water. A third portion is heated in water acidulated with sulphuric acid, organic acids being thus set free and dissolved, and sulphates of alkaloids also extracted. The fourth operation is-digestion in water rendered alkaline by ammonia, and for this the residue of the first operation may be em ployed. A fifth portion is subjected to the solvent action of alcohol, either cold, hot, strong, or weak, according to the nature of the material under examination ; fats, oils, resins, and many bodies insoluble in water being thereby dissolved. The sixth process consists in treating with ether, which much resembles alcohol in its powers of solution, but differs in its action upon free fatty acids, and one or two other important bodies.