A RETROSPECT.

WITH the present number the CHEMICAL NEWS begins the fifty-first year of its existence. It made its first appearance December 10th, 1859. A brief recapitulation of the objects and aims it was intended to fulfil, and some account of its career, will probably interest those subscribers who have not followed its fortunes from the beginning.

In 1859 most of the present day scientific periodicals did not exist, and the spread of chemical knowledge was slow and restricted. Thus the Berichte der Deutschen Chemischen Gesellschaft is quite the younger brother of the CHEMICAL NEWS, and the German Chemical Society of Berlin was not founded till 1868. In the early fifties there was no weekly English newspaper to record the rapid advances of chemical science either in this country or on the Continent. The Journal of the Chemical Society was then as now a valuable record of the work of English Chemists; it was not until much later that it began to publish stracts of Papers from Continental chemical urnals. These extracts were recognised as of extreme importance, and by their aid English Chemists were easily placed au courant of the latest researches and discoveries of their foreign fellow workers.

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The great chemists and physicists of those days contributed many priceless Papers to the early volumes of the CHEMICAL NEWS. Frankland, Kolbe, Graham, Liebig, Faraday, Tyndall were all eagerly researching, probing, verifying, and building-up the knowledge; while Mendeleeff and Kekulé, Kirch off and Bunsen had far from exhausted their amazing hypotheses and discoveries. The first announcement of the discovery of the element Thallium was given to the world in our third volume. In addition many of the brilliant eager younger men were coming to the front, and it is to the CHEMICAL NEWS they looked to spread the knowledge of their hitherto unrecognised work. Many of these early contributors are still amongst us, and time has proved that the CHEMICAL NEWS showed judgment and sagacity in publishing their first researches. Faraday's famous lectures before the Royal Institution on "Various Forces of Matter" and on the "Chemical History of a Candle" were

reproduced verbatim in the first volume. Tyndall's Lectures were also fully reported. Frankland's remarkably lucid discourses on "Inorganic Chemistry," which summarised practically all that was then known of the subject, are still worth reading, and clearly show how the way was paved for subsequent discoveries.

Turning over the pages of the early volumes one cannot but be struck with the thought how much was known, and again how much was not known, in the last half of the nineteenth century. Thus, organic chemistry and the doctrine of the atom were already sturdy developments of the earlier decades. The period of the discovery of fresh elements must be put a little earlier, though announcements of great importance upon this subject followed rapidly. Spectral and microscopic analysis were both in their infancy, although the germ of the modern doctrine of valency had practically been contained in Frankland's work on the organo-metallic derivatives. Photographic chemistry was in some respects well advanced, and technical chemistry was growing with unparalleled rapidity. On the other hand, many important undecided questions were freely discussed in the pages of the CHEMICAL NEWS. At the time of the appearance of the earlier numbers the formula of water was written HO, and that of potassium nitrate KNO6, isomerism and stereo-isomerism had not as yet found an explanation, the cathode rays had not been detected, and physical chemistry was practically unknown. The reaching of high temperatures was an achievement to be reported in a later volume, and low temperature research was of a still later date; while the sister science of radio-activity, with its powerful influence upon the whole trend of modern thought, was not even in the realm of dreams. Many important discoveries in technical chemistry, such as the application of scientific methods to manufacturing processes and to the solution of agricultural problems, &c., were later developments. The knowledge of chemistry possessed by the general public was infinitesimal, an ignorance due partly to lack of facilities. Above all it is strange to reflect that in 1859 the Periodic Law was unknown. This great generalisation which has thrown so much light upon the meaning of chemical phenomena had not yet been put before the scientific world. Newlands' "Law

Speaking generally, the period beginning 1859 was rather a period of the investigation of details both in organic and inorganic chemistry than an age of great generalisations; and the work of most original investigators consisted of the patient accumulation of information upon lines already well and clearly defined. Possibly we are now on the brink of the formulation of a new set of laws epitomising and bringing together what appear at present to be unrelated and isolated facts. The time seems ripe for fresh generalisations.

And how has the CHEMICAL NEWs fulfilled its aims? Looking back upon its career can it be said to have performed the two-fold task of the truly useful scientific paper-the giving of assistance in the advancement of knowledge by the specialist and the spreading of knowledge among the public? There is no question but that among its contributors have been numbered great minds, specially endowed, to whom it is given to discover, to invent, to devise, and to perfect. Many discoveries of astonishing import have been announced in its pages, and workers of all nations have acknowledged the CHEMICAL NEWS to be a source of inspiration, an incentive to fresh effort. Its pages have always been open to unknown writers, and new ideas and conceptions have been frankly welcomed. Revolutionary doctrines have been freely discussed, and Progress has ever been the watchword. In the early numbers of the CHEMICAL NEWS many semipopular expositions of scientific subjects were included, so that chemistry and physics might become less of a mystery to numbers who readily would have devoted themselves to the study of science, but whom circumstances debarred from following their true bent. Thanks to the spread of scientific education there is now little need to consider this class of readers. Practical men will still find in every issue helpful suggestions, and chemists, prevented by lack of linguistic talent from following the researches of workers of other nationalities, have also reason to be grateful for full abstracts from foreign periodicals.

The CHEMICAL NEWS has always been tolerant, open-minded, and impartial. Regardless of consequences it has pursued one great aim-the true furtherance of Science. Who can estimate the value of services rendered to the public in exposing the evils of food adulteration, pointing out the need for better methods of analysis, greater watchfulness, and greater skill on the part of those entrusted with the work? When methods of analysis of foods and drugs, for the detection of poisons and deleterious materials, were as yet imperfect, and the shortcomings of any method were freely admitted, no false esprit de corps silenced its voice in cases where possibly either faulty methods or want of knowledge had led experts to false conclusions. The earlier numbers contain many discussions on

Fifty years have not passed without their testimony to the unforeseen conclusion of many controversies, the superseding of methods at one time regarded as infallible, and the overthrow of hotly supported theories. The Editor can but hope that the CHEMICAL NEWS has not fallen short of the true aim of all scientific work-the advancement of the sum of human knowledge.

Vast as have been the discoveries of the past, marvels are still unfolding. Great spirits have departed and left their mark-and "great spirits now on earth are sojourning."

Thus tantalum is used for the filaments of electric lamps, for current rectifiers, for the construction of useful objects such as pens, &c. Titanium has recently been employed in the manufacture of steel, for it is said to communicate useful properties to iron (W. Venator, "Uber Eisenlegierungen und Metalle für die Stahlindustrie," Stahl und Eisen, 1908, Nos. 2, 3, 5, and 8). As yet no technical use is known for niobium.

covering methods for the quantitative determination of the The experimental investigation therefore aimed at disacid earths and their preparation in the pure state.

In the description of the different experiments it will be best to discuss, first, the preparation of the pure acid earths, and to show how they are separated from one another and from the metallic impurities accompanying them; then the quantitative determination of the individual acid earths will be described, and the separation of them from one another.

Finally, some analyses will be given of such tantalum, niobium, and titanium minerals as are worked up technically.

In conclusion, we shall endeavour to give a comprehensive survey, based on the knowledge obtained, of the properties of the acid earths from an analytical point of view.

We had at our disposal nearly 3 kgrms. of impure material containing niobic acid; it had been prepared in the course of earlier experiments in this laboratory.

The impurities present in this niobic acid were titanium, tin, iron, and ammonia, the last in all probability due to the fact that the material had been ignited with ammonium carbonate in order to remove the sulphuric acid present. It is known that it is a peculiarity of niobic acid if it is precipitated with sulphuric acid to retain the greater part of it in spite of repeated washing, and not to give it up even when very strongly heated.

* From the Zeitschrift für Anorganische Chemie, Ixiv., 65.

Wöhler (Pogg. Ann., xlviii., 91) therefore suggested the addition of ammonium carbonate on ignition, in order thus to volatilise the sulphuric acid as ammonium sulphate. This method has, however, various disadvantages, for it is impossible, especially on stirring, to prevent the niobic acid from spirting, owing to the sudden formation of vapour, and the complete removal of the sulphuric acid cannot be effected even when the ignition process is repeated. Moreover, as we have found, niobic acid can never be completely precipitated by boiling with sulphuric acid, and it is almost impossible to filter it owing to the form in which it separates.

These difficulties are easily overcome if the acid is neutralised with ammonia in very slight excess. When precipitated whilst warm the niobic acid is rapidly deposited in beautiful white flakes; the liquid above it is perfectly clear and can be filtered very easily. This precipitate can also be separated particularly well in a Nutschen filter.

If the precipitate is washed with water containing ammonia (one-half per cent) it is perfectly free from sulphuric acid after the first ignition.

Precipitated niobic, tantalic, or titanic acid must never be washed with pure water, for the liquid always goes through the filter turbid, especially if the precipitate has been nearly freed from electrolytes (ammonium salts); by using one-half per cent ammonia for washing this difficulty is entirely avoided. If it is necessary to wash the precipitates with water containing acid, a dilute (about 1 per cent) acetic acid solution can be used, but not a mineral acid; thus it was found that the precipitated acid earths-in the hydrated state-are comparatively easily soluble in mineral acids. Hydrochloric acid dissolves them more easily than nitric acid, and the latter more readily than sulphuric acid. In perchloric acid the substances, are, however, quite insoluble.

It is always an advantage, after washing with acetic acid, to rinse with water containing ammonia, as otherwise the filter is apt to crumble when it is dried.

Returning after this digression to the initial material, it must be added the niobic acid used was free from tantalic, sulphuric, and silicic acids.

To test for tantalic acid, some granules of the niobic acid were dissolved by warming with hydrofluoric acid and neutralised with potash solution. After being diluted strongly, a drop of this solution was evaporated on the slide, and subjected to examination under the microscope (Weiss and Riedelbauch, Ann., ccclv., 61). The double fluoride crystals thus obtained did not contain the exceedingly characteristic lance-shaped crystals of potas sium tantalum fluoride, but exhibited the tablet shape of niobium potassium oxyfluoride.

We had only 20 grms. of tantalic acid, but it was perfectly pure. We had in addition various specimens of socalled purest tantalic and niobic acids, as they are obtained at a very high price from the usual chemical manufacturers. All these preparations, in spite of the descriptions applied to them, were exceedingly impure; we have sometimes even found that "sodium tantalate or niobate purissimum consisted of nothing but an ordinary mixture of acid earths without containing alkali, and having in it iron, tin, and even unchanged mineral. It will readily be understood that working with such material, which is called chemically pure, involves much waste of time, and one is easily led to false conclusions. The extraordinary confusion in the statements in literature on the acid earths is partly explicable by this “very deplorable" state of the chemical trade.

II. METHODS OF PURIFICATION.

A. Older Methods.

The older methods of Rose (Pogg. Ann., lxiii., 307, 693; lxix., 118) and Marignac (Ann. Chim. Phys., [4], viii., 5, 49) only differ as regards the opening up of the mineral used.

The former fused the acid with soda and sulphur in order

to get the tungsten and tin into solution as polysulphides. The latter fused the acid with potassium monosulphate, and extracted the melt with hot water, boiled to separate the niobic or tantalic acid, digested the residue with ammonium sulphide to remove the tungsten and tin, and treated the residue with hot concentrated hydrochloric acid to dissolve the iron sulphide formed; after filtering and washing he obtained the pure acids. Rose removed the iron in the same way as Marignac.

But this method of separating iron involves the wastage of much material, as the hydrochloric acid dissolves a considerable amount of the niobic or tantalic acid. In Marignac's method of obtaining pure acids large quantities of them are also lost, for on boiling the potassium sulphate melt with water the complete precipitation of the two acids can never be attained. Moreover, both acids very persistently retain iron on washing; filtration is very difficult, as we have said above, and washing with water always makes the liquid which runs through turbid.

B. Modern Methods.

Above all we tried to effect the removal of iron from the niobic acid by a more rational and, as far as possible, quantitative method.

Freshly precipitated niobic and tantalic acid dissolve readily in caustic soda. But the former is partly re-precipitated in the form of sodium niobate by a large excess of the alkali.

Sodium carbonate also readily dissolves both acids when they are freshly precipitated, and keeps them in solution even when present in large excess. Tantalic acid dissolves less easily than niobic acid. Sodium bicarbonate solution dissolves neither niobic nor tantalic acid. Ammonium carbonate does not dissolve either acid.

All the above reagents lose their solvent power if the acids have previously been heated to 100°, and their solubility shows a decided decrease if they have stood for some time for more than a few hours-without being covered with aqueous solutions, at the temperature of the room.

Very considerable difficulties are encountered when large quantities of the acid earths are to be separated from iron by extracting the precipitate with hot soda solution, because the solution of the acid earths proceeds comparatively slowly, and because the filtration and washing of the precipitates containing iron takes so much time that the acid earths become difficultly soluble. The iron hydroxide residue persistently retains the alkali compounds of the acid earths, and very large quantities of liquid are obtained if the washing is in any degree complete.

From the alkaline solution of the acid earths, niobium and tantalum are best precipitated with acetic acid in the hot solution; if, however, a mineral acid is used ammonia must subsequently be added till the liquid gives an alkaline reaction.

Another method of separating the iron depends upon the difference in the behaviour of iron and a mixture of the two acids towards oxalic and tartaric acids.

Freshly precipitated iron hydroxide dissolves very easily in oxalic or tartaric acid. From the former solution it is again completely precipitated by the usual reagents, such as, for example, ammonia, &c., in presence of not too large an excess of oxalic acid. When it is dissolved in tartaric acid, only ammonium sulphide possesses the property of decomposing the compound and precipitating the iron as ferrous sulphide.

Freshly precipitated niobic and tantalic acids also possess the same property as iron hydroxide. They are precipitated by the ordinary reagents from oxalic acid solution, but the compound formed with tartaric acid resists the action of ammonium sulphide; from oxalic-tartaric solution none of the known reagents can effect precipitation.

It was thus to be expected that in oxalic-tartaric solution the use of ammonium sulphide would completely separate the two acids from iron. Experiments based upon this assumption confirmed this conclusion,