Scientific Serials

Abstract

THE Journal of the Chemical Society for October contains but one paper communicated to the Society, viz., a lengthy communication on the chemistry of tartaric and citric acids, by Mr. R. Warington. The author has had considerable experience in the manufacture of these acids, having been for some years chemist to the factory of Mr. J. B. Lawes. The author's experiments prove that the citric acid of commerce contains one molecule of water corresponding to the formula C6H8O7, H2O. Some interesting results have been brought to light in the course of some experiments made with a view to determine the water of crystallisation in various samples of the acid. Thus in one determination a specimen of the powdered acid lost the whole of its water over sulphuric acid in a few days, at a temperature of 16°. In another experiment the powdered acid lost but a mere trace of water in vacuo over vitriol for some days, while the same acid heated to 100° lost its normal amount of water. Results of an equally contradictory nature were obtained with various other samples of the acid tried at subsequent periods. It has been proved also that a strong solution of citric acid undergoes considerable contraction when mixed with water. —The next section of the paper relates to the acidity and commercial value of the different lime, lemon, and bergamot juices supplied for the manufacture of citric acid. The nature of some of the acids existing in the concentrated juices is to be made the subject of further research; up to the present time, in addition to citric, formic, acetic, and possibly propionic, acids have been detected. It appears, however, that the organic acids other than citric which exist in the juice are chiefly non-volatile, and have soluble calcium salts. Phosphoric acid has also been found, and there is reason to suspect malic and aconitic acids, the latter being produced by the concentration of the juice. With regard to calcium citrate, it has been found that the amount of water contained in this salt varies according to the mode of preparation, a result demanding further investigation. The author next gives details of the method employed for analysing the citric acid liquors. With regard to tartaric acid, it is found that a strong solution contracts even more than citric acid when mixed with water. The author then proceeds to consider the qualitative reactions of tartaric, metatartaric, and ditartaric acids. Contrary to the statement given in books, it has been found that calcium acetate yields a crystalline precipitate of calcium tartrate, even in dilute solutions of tartaric acid. Free tartaric acid also is precipitated by calcium chloride in the presence of alcohol. The reactions with the acetates of lead and barium have likewise been studied. With regard to the amount of water in calcium tartrate, the author concludes that the salt has no definite composition at 100°. A very complete series of experiments upon the solubility of potassium bitartrate has been made, and the remainder of the paper is devoted to the materials used for the manufacture of tartaric acid, viz. lees, argol, and tartar, and the methods of analysis employed in their valuation. Mr. Warington deserves credit for thus contributing to the general store of knowledge from the experience gained in the chemical factory. A great deal of manufacturing chemistry is at present carried on without any regard to the scientific principles involved, and if manufacturers would only be somewhat more free in communicating apparently inexplicable facts to the scientific world, the advantage gained could not but be mutually beneficial. To quote the author's own words:—“A large amount of information is acquired in the laboratories of our great manufacturing concerns; most of this might be published without any injury to the individual manufacturer. Especially is this true of analytical methods, and the publication and discussion of these would do much to remove the disgrace to which science is often subjected from the wide discrepancies of commercial analyses.” We cordially echo the hope “that the publication of these notes may lead to many similar communications.”—The remainder of this part is occupied by abstracts of papers from British and foreign journals.