NEW METHOD FOR THE QUANTITATIVE DETERMINATION OF STARCH.
A.V. ASBOTH.
The author maintains that unsatisfactory results are obtained in determinations of starch when the method employed is based upon the inversion of sugar, formed as an intermediate product, since maltose, dextrose, and levulose are partly decomposed by boiling with dilute acids. He proposes to replace the methods hitherto employed by one which depends upon the formation of a barium salt of starch, to which he assigns the formula BaO.C24H40O20. This salt is sparingly soluble in water and insoluble in dilute alcohol.
In making a determination a weighed quantity of starch is saccharified with water, then mixed with an excess of normal baryta solution, dilute alcohol added to make up to a certain volume, and, after the precipitate has settled, the excess of baryta is titrated back with acid.
Titrating apparatus
The author also describes the apparatus he employs for storing and titrating with baryta solution. The latter is contained in the bottle, A, and the drying tube attached to the neck of the same is filled with quicklime. The burette, B, which is in direct connection with the bottle, may be filled with the solution by opening the stop cock, and the small drying tube, n, is filled with dry KOH, thus preventing the entrance of any CO2. Numbers are appended which seem to testify to the excellence of the method employed. The author finally gives a detailed account of the entire analysis of various cereals.—A.R. in Jour. Soc. Chem. Indus.
SYNTHESIS OF THE ALKALOIDS.
In the note on the constitution of alkaloids in a recent issue, we referred more especially to what we may term the less highly organized bases. Most of our knowledge, as we now have it, regarding such alkaloids as muscarine and choline has been acquired during the past dozen years. This is not exactly the case with the higher groups of alkaloids—the derivatives of pyridine and quinoline. It so happens that the oldest alkaloids are in these groups. They have, almost necessarily, been subjected to a longer period of attack, but the extreme complexity of their molecules, and the infinite number of differing parts or substances into which these molecules split up when attacked, are the main cause of the small progress which has been made in this department. All, however, yield one or more bodies or bases in common, while each has its distinctive and peculiar decomposition product. For example, cinchonine and quinine both afford the basic quinoline under certain conditions, but on oxidation of cinchonine, an acid—cinchoninic acid (C10H7NO2)—is the principal body formed, while in the case of quinine, quininic acid (C10H9NO3) is the principal product. The acquirement through experiment of such knowledge as that is, however, so much gained. We find, indeed, that obstacles are gradually being cleared away, and the actual synthetic formation of such alkaloids as piperidine and coniine is a proof that the chemist is on the right track in studying the decomposition products, and building up from them, theoretically, bodies of similar constitution. It is noteworthy that the synthesis of the alkaloids has led to some of the most brilliant discoveries of the present day, especially in the discovery of dye stuffs. Many of our quinine substitutes, such as thalline, for example, are the result of endeavors to make quinine artificially. If there is romance in chemistry at all, it is to be found certainly in this branch of it, which is generally considered the most uninteresting and unfathomable. We may take piperidine and coniine as examples of the methods followed in alkaloidal synthesis; these are pyridine bases. Pyridine has the formula C5H5N, that is, it is benzene with CH replaced by N. The relationship between these and piperidine is seen in the following formulæ: