3. Chromates.-Dr. John has published a paper on the chromates, in which he describes the properties of twelve chromates hitherto unknown, or nearly so. As this paper is short, and cannot well be abridged, I have inserted a translation of it in the last number of the Annals of Philosophy, to which I refer the reader. 4. Sal-ammoniac.-Before concluding this department, I may take the opportunity of mentioning that Mr. Trimmer informs me that the sand employed for mixing with the clay by the London brick-makers is brought from below Woolwich. It probably, therefore, contains some common salt, derived from the sea water with which it is washed. This may be the source of the muriatic acid which goes to the formation of the sal-ammoniac that sublimes during the burning of the bricks; but if this be the case, Nature employs during this process some method of decomposing common salt at present unknown to manufacturers; but which it might be well worth their while to endeavour to trace experimentally, unless we suppose the whole acid to come from the muriate of magnesia, VIII. Composition of Alcohol and Ether. M. de Saussure has given us a new, and seemingly very accurate, analysis of alcohol and sulphuric ether. The constituents of alcohol are as follows: This result seems to show that alcohol is composed of An atom of it, according to this statement, would weigh 2·898. This composition is very simple, considering that the number of constituents of alcohol amounts to three. The constituents of sulphuric ether are, This result seems to show that sulphuric ether is composed of So that, if the analysis of Saussure be correct, sulphuric ether contains twice as many atoms in its composition as alcohol. The weight of an integrant particle of it, according to this statement, would be 5.547. IX. Analysis of Waters. Bouillon-Lagrange and Vogel have published an elaborate analysis of the sea-water that washes the different coasts of France. The following table exhibits the results of their analyses : Water of the Channel...... 1000 Gram. Gr. Gr. Gr. Gr. Gr. Gr. Gr. 0.15 0.15 38 0.23 25.10 3.50 5.78 0.20 Water of the Atlantic...... 1000 0.15 Berzelius has published an analysis of a very complicated mineral water in Stockholm. Its constituents per Swedish kanne are as follows: According to the analysis of Mr. Funke, apothecary at Linz, on the Rhine, the mineral water of Tönnestein, on the Rhine, contains the following constituents in five pounds weight of it : Five pounds weight of the mineral water of Heilbrunn contains, according to the same analyst, The same chemist obtained the following substances from five pounds of the mineral water of Obermenning : Finally, the mineral water of Heppingen gave the same chemist the following ingredients. He operated, as before, upon five pounds of the water : The field of vegetable chemistry is so vast, and still so imperfectly explored, that it is always a very prolific department. I must at present confine myself within as narrow limits as possible, and avoid indulging reflections even when they obtrude themselves upon me. 1. Tribet Caoutchouc.-This is a reddish elastic substance, which is used as beads in the Mediterranean. I have seen strings of beads repeatedly brought to this country from Malta, and once made a few trials on one of these beads, sufficient to show that it was a vegetable substance, and that it had some resemblance to the oils in its chemical properties. It has been particularly examined by John and Bucholz. Neither alcohol, ether, nor oils, dissolve it completely, thoughthey produce some effect on it. Potash ley dissolves it, and an acid separates it from the solution in the state of an oil. It dissolves in sulphuric and nitric acids. When heated, it does not melt; but it soon loses its red colour; it seems to me to be very analogous to linseed oil boiled to dryness. Nothing is known respecting its natural history. It is probably a natural production. It is said to be much employed in Thibet. Whether what is used in the Mediterranean comes from Thibet I do not know. 2. Cajeput Oil.-This oil has lately acquired considerable celebrity in some parts of England, as a most effectual remedy for rheumatism when applied externally to the diseased part by friction. It was first made known in Europe by the Dutch. According to Murray, it was first brought to Holland about the beginning of the eighteenth century. In 1719 it made an article in the Materia Medica in some of the German Pharmacopoeas. It is doubtless an essential oil. Dr. Roxburgh has lately laid a very accurate account of the tree which yields this oil before the Linnæan. Society. He cultivated these trees at Calcutta for about ten years; so that the doubts still remaining respecting the nature of the plant from which this oil comes may be considered as removed. 3. Sugar from Starch.-Kirchhoff's discovery of the method of converting starch into sugar was no sooner known in Germany than it occasioned a great many publications on the subject, and numerous attempts to improve the process, and render this new sugar a substitute for common sugar. These attempts were natural at a time when the mistaken policy of Bonaparte had shut out Europe from all access to foreign countries, and precluded the supply of common sugar, except at an enormous price. I cannot find, however, that any of these attempts were attended with success; or that much additional chemical information, was even added to Kirchhoff's original discovery. This discovery was owing to an accident. In consequence of the war between Great Britain and Russia, the Russians found it difficult to procure gum. Kirchhoff's object was to render starch a substitute for gum. He thought that he would improve it by boiling it in weak sulphuric acid. He gradually lengthened the boiling process, in expectation of rendering the starch more completely gum. The result was, that it acquired a sweet taste, and the properties of sugar. Schrader has shown that by increasing the quantity of sulphuric acid the length of time necessary for boiling inay be shortened. Thus five or six parts of sulphuric acid to 100 parts of starch require only six or eight hours boiling. Nasse found that nitric acid and muriatic acid produce this change on starch as well as sulphuric acid. Starch sugar is not so sweet as common sugar; but I have seen it as white, and very like common loaf sugar in appearance. 4. Sap of the Acer Campestre.-In the year 1811 Professor Scherer, of Vienna, examined the sap of the acer campestre, or common maple, with a view, I presume, to the sugar which might be extracted from it. This sap, when in small quantities, was |