THE E S T I N A T I O N O F T I T A N I U M .
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in these tables. T h e yellow color is probably somewhat easier to “match” than the pink, and its use is advised when the higher concentrations are concerned. I t is also of considerable advantage in that it affords a ready check upon the determination by the pink color, a matter of importance when such small amounts of unknown solutions are available as to preclude duplicate determinations. The yellow color is not so deep or strong, however, as the pink, and for this reason the latter is much more advantageous than the former, when high dilutions are concerned. From what has been presented in this paper, it is evident that we have here a very sensitive method, susceptible of a high degree of accuracy, for determining quantitatively minute quantities of potassium. No unusual apparatus o r skill is required for its manipulation. But it will only yield satisfactory results when care is exercised, and especially in the handling and washing of the small precipitate of potassium platinic chloride. The limit of dilution tu which the method is applicable is probably much higher than the figures given here would indicate, but we have not attempted to determine this limit, and are not prepared to make a more definite statement concerning it. BUREAUO F SOILS, U. S . DEPARTMENT O F AGRICULTURE, WASHINGTOS. I).
c.
THE ESTIflATION OF TITANIUfl. B Y J.
WATSONBAIN.
Rccelved August 17.
xwj.
OF THE many elements which present themselves for determination to the metallurgical chemist of to-day, there are a select few which have won for themselves a reputation based upon the tediousness or the difficulty of the preliminary separation from other constituents which may be present. I n this class of unenviable reputation we may place the element titanium for, although its determination presents no difficulties t o the experienced chemist with time at his disposal, his less fortunatc brother, a t the same task in the rush of a works laboratory, is apt to find that either speed or accuracy must be sacrificed in answer t o the demands made on him. F o r three-quarters of a century the estimation of this element
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R.LIS.
in all pure solutions involved six or eight hours' boiling, an oppration which had often to bc repeated, or else a tedious treatment with ammonium s u 1ph id e, until Goocli discovered that tit ani tuii could be precipitated quantitatively i n a convenient form by a few minutes' boiling, and Elair: added to this a tnodificatioii which permitted a much niorc rapid separation from iron thai: heretofore. Thus the determillation became comparatively cnsy, but nevertheless under the pressure of heavy work and insufficient time, the demand for a shorter method has become notice. able and i n response several modified processes have appeared in the chemical literature of the cia!.. To inquire into the accuracy of these was the first object of the following investigation. A4t the same time it has not been considered necessary to confine thc attention to speed, and hence some experiments have lieen incorporated simply because they have a bearing upon the estimation of titanium i n general. In the foregoing statements, therc has been a reservation regarding excellcnt colorimetric method ; it is rapid and accurate, but unfortunately is only adapted for the estimation of small quantities of titaniuni. To the chemist engaged i n the analysis of minerals and roc!.:: the separation of titanium from some of the rarer elements such as zirconium or vanadium is a matter demanding attention, but t o the metallurgical chemist who meets these more uncominoi~elements either rarely or in minute quantities, the eliininatioii of iron, aluminum and phosphorus is mually the only problem to be considered. For this reason, the behavior of these last three elements, with the one under consideration, has been the object of this study. At the same time it will readily be seen that all our present lmowledge can be directly employed in the final stages of any of the methods investigatctl. Without referring in detail to the modifications of the older processes, descriptions of which a r e to be found i n modern chemical or metallurgical journals, it is proposed to discuss the merits of three methods which are apparently new in principle. I n the foilowing pages, these have been designated for convenience by the author's name; i f any injustice has been done, the Ivriter begs to offer his apologies. i(. A . , 1 Gooch ; Bull. 27, U. S. Geol. Survey. p. 16 : Proc. . 4 m . A c a d . A ) is .S
