ABOUT 1820 chrome ores were first introduced in considerable quantities for the manufacture of chromium salts, and naturally the quantitative determination of the amount of metallic chromium contained in them received much attention at the hands of chemists. Calvert 1852 (1), Bunsen 1854 (2), and Woehler (4) some years later were the first to devise satisfactory quantitative methods for the analysis of chrome ores, but these methods were very incomplete and would hardly satisfy the modern chemist. Since then chromium has taken a very prominent place in chemical industry, and the literature referring to the determination of it has increased in proportion to its use in the production of various salts, chrome paints, ferro-chromium, chrome-steel, &c. tions Na2CO3, K2CO3, KNO3, KCIO3, KHSO4, KF, Na2B4O7, &c., &c. Some of these methods gave satisfactory results, and have found a very extensive application, as, for instance, the so-called magnesia-method of Dr. J. Clark (14), which was proposed by him as early as 1871. It may be interesting to mention that six years later Christomanos (20) proposed the above mentioned method as one which had been carefully worked out by himself, for the decomposition of chrome ores. He communicated the very accordant results of about 50 different chrome ores, and thus once more proved the exactness of the magnesia-method, the priority of which undoubtedly belongs to Dr. J. Clark. Another reagent for the decomposition of chrome ores has lately been proposed by J. E. Stead (32). It is the so-called tri-basic reagent, consist. ing of a mixture of 4 parts lime, I part Na2CO3, and I part K2CO3, which readily effects a complete decomposition. A very similar mixture, viz., 2 parts Na2CO3 + 3 parts Ca(OH)2, was proposed in 1876 by Dr. R. Kayser (17). In all the methods suggested for the decomposition of The list of papers on this subject which we have chrome ores and alloys special stress was laid upon selected, and which, as regards the analysis of chrome- rendering the time required for complete decomposition steel, is still far from being complete, will give some idea as short as possible, and this point, as far as the works. of the importance of the subject and of the number of analyst is concerned, is naturally of great importance. eminent chemists who have made a special study of it. The methods previously mentioned fulfilled this conIn the proposals which have been made for the quanti-dition in so far that they reduced the time necessary for tative analysis of the chrome ore or of ferro-chromium, complete decomposition from about 4 hours to 1 to 2 the chief difficulty has been in obtaining a convenient hours. method for rendering the chromium soluble. The gravimetric methods of determining the chromium from its solutions were soon abandoned as requiring too much time, and two volumetric methods, viz., the permanganate method of H. Schwartz ("Fresenius Quantitative Anal.," i., §112, 2a), and the bichromate method of Penny ("Fresenius Quantitative Anal.," i., §112, 26) have since been universally adopted. The chief problem, viz., the complete decomposition of the ore or of its iron alloy remained for a long time unsolved, and the most widely differing methods have from time to time been proposed for this purpose. It was soon found that a wet decomposition by means of acids in combination with oxidising agents would not produce the desired effect, so that almost all the subsequent methods which were proposed for the decomposition of chrome ores or alloys are based on the oxidising action of mixtures containing in varied proportions and combina. With the introduction of sodium peroxide for laboratory use the decomposition of chrome ores and alloys enters into a new phase, and W. Hempel (34) was the first to draw the attention of chemists (in 1893) to the use of this leagent for effecting the decomposition of chrome ores. The experiments which he made were only of a qualitative nature, but during the same year J. Spueller and S. Kalman (35) in Germany and Dr. J. Clark (36) in this country adopted sodium peroxide for the quantita tive analysis of chrome ores and alloys, and especially the two first-named chemists succeeded in working out an exact method for the analysis of chrome ore, ferrochromium, and chrome steel. The chief claim made for the sodium peroxide was the extraordinary rapidity with which a complete decomposition could be effected, provided that the ore was reduced to a very fine powder. E. H. Saniter (40) has quite recently also published a |