THE CHEMICAL NEWS

VOL. CVII.. No. 2787.

ATOMIC WEIGHT ESTIMATION FROM SPECIAL GROUPINGS OF THE HYDRIDES.

By F. H. LORING.

THE estimation of atomic weight by means of tabular schemes is well known, and a very high degree of perfection in this method was reached by Mendeléeff in his studies.

Since the radio-active elements have been discovered, many efforts have been made to arrange these more or less transient bodies in special periodic classifications.

With the advent of a more thorough chemical knowledge of the radio-active elements, several successful attempts have been published. A considerable number of papers on the valency and classification of these elements have appeared this year :

G. v. Hevesy, Phys. Zeit., xiv., 49; Phil. Mag., xxv., 390; Le Radium, x., 65; Zeit. Elektrochem, xix., 291; K. Fajans, Phys. Zeit., xiv., pp. 131, 136; Le Radium, x., pp. 61, 57; A. S. Russell, CHEMICAL NEWS, cvii., 49; F. Soddy, CHEMICAL NEWS, Cvii., 97; Nature, xci., 57; fahrbuch d. Radioakt., x., 188; A. Schuster, Nature, xci., 30; N. R. Campbell; Nature, xci., 85. Some of these papers cover the same ground.

In a few of these principal communications, which bear directly upon the valency and periodic classification of the radio-active elements, it may be of interest to observe that the atomic weight of actinium has been estimated at 226.5 (Fajans) and 230 (Soddy).

It may also be worth while noting that special classifications of the hydrides would seem to afford a means of fixing approximately certain atomic weights, in particular those of radium and actinium.

Unfortunately, however, just where the greatest assistance is needed in arriving at the magnitude, two assumptions have to be made; first, that the element in question forms a hydride of a particular type; and secondly, that the special arrangement is, in general, accurate or applicable. Nevertheless, Tables I. and II. (diagram) may be of interest, notwithstanding their artificial nature. The fact that high authorities have agreed that the atomic weight of actinium is probably near to that of either radium or thorium is perhaps sufficient reason for venturing further in the direction of extrapolation than one would otherwise do. Inasmuch as the tables are self-explanatory, no special comment need be made, except to call attention to the possibility that J. J. Thomson's X3-gas is perhaps HH2, since copper yields two types of hydrides, and the uniformity of the table is improved thereby. That is to say, such a compound would find a place in the table and give it a more symmetrical appearance. Thomson gives reasons based upon experiments for not expecting hydrogen to form a compound" H3." Still the point is not settled (see Nature xc., 645).

Radium being closely allied to barium, and actinium to lanthanum, perhaps justifies, in a measure, the assumptions that these elements are capable of forming hydrides as shown.

The straight lines in the diagrammatic table bring into prominence a fact observed before, that the irregularity in the atomic weight of tellurium is shared to some extent by selenium, since it is not supposed that the atomic weights are sufficiently in error to expect the values to fall exactly on a straight line. The method therefore not being exact, one is led to expect the atomic weight of actinium to be in the neighbourhood of 230.

Of course some of the hydrides shown in these tables are extremely unstable, and their formulæ are not all confirmed by vapour density determinations.

It may be that a classification based upon the atomic values within a bracket-(MH)n-are the ones which will lend themselves to a more systematic treatment (see copper in Table II.). [M= element other than hydrogen; H = hydrogen; n and n' = numbers 1, 2, 3, &c.].

Royal Institution.-On Tuesday next, April 29th, at 3 o'clock, Prof. William Stirling begins a course of three lectures at the Royal Institution on "Recent Physiological Inquiries." Owing to the illness of Prof. Bateson, his course of lectures on "The Heredity of Sex and some Cognate Problems" has been postponed. In addition to those Friday Evening arrangements already announced, Discourses will probably be given by Mr. F. Balfour Browne, Capt. C. G. Rawling, Prof. Silvanus P. Thompson, Mr. Owen Seaman, and Dr. Francis Ward.

THE TESTING OF SAFETY EXPLOSIVES.*

By Prof. VIVIAN B. LEWES, F.I.C., F.C.S., &c.
(Continued from p. 190).

IN making the dust-and-air mixture, its sensitiveness will depend upon (1) the ease of ignition of the dust, the degree of fineness to which it is reduced, and the other factors which have been studied so fully at Altofts and Eskmeals, one of the most important being its freshness; (2) the percentage of dust to air at the moment the shot is fired into it; and (3) the percentage of oxygen in the air.

Through the courtesy of Major Cooper-Key, I obtained a sample of the dust used at Rotherham, which is made by grinding coal from the 7-ft. seam of the Birchen wood Colliery, North Staffordshire, to a powder that will pass a 150-mesh sieve. On analysis, the dust gave :

It is evident, therefore, that if the coal-dust be suspended in pure air with a percentage of 2019 of oxygen, as soon as the temperature is raised for a sufficient length of time to 400° C. the dust will ignite.

In the second report of the Explosions in Mines Committee, the "relative ignition temperatures" of a long series of coal-dusts, as determined at Eskmeals, are given, and out of fifty dusts two only are credited with an ignition temperature below 1000° C. (i.e., 950° C.), and four are above 1400° C.

Amongst these the sample N 216 has much the same proximate composition as the Rotherham dust, and is credited with a "relative" ignition temperature of 1065° C. An examination of the method employed shows that what has been determined is the relative ease of ignition under certain circumstances, and has nothing to do with the ignition point. Coal dust has been blown at a definite pressure through a glass tube, across which a spiral of platinum wire, coiled on a quartz tube, was arranged and heated to measured temperatures, and the degree at which the rapidly passing cloud caught fire was the "relative" ignition temperature.

The Eskmeals experiments are of great interest from another point of view. We saw that the French Commission found that methane, or, rather, pit-gas, inflamed at a temperature of 650° C. continued for ten seconds, but needed a much higher temperature to give immediate ignition, and it appears probable that coal dust, although ignited by a heat of 400° C. continued for a few seconds, requires a temperature of over 1000° C. for immediate ignition; but further experiments are needed to establish this point, as extended experience will probably show that the gases occluded in the coal dust, especially oxygen, play an important part in the temperature at which ignition takes place, and the dusts tested at Eskmeals were all dried at 107° C. for an hour before being experimented | with, which would expel gases or, in any case, alter their

nature.

These points, however interesting from a theoretical point of view, have but little to do with the subject we are discussing, and the fact remains that the dust used at Rotherham is sensitive, is all obtained from one seam in the same colliery, and is either freshly ground for each testing, or is kept from contact with air in sealed tins, so that every requirement is satisfied.

We next come to the influence of the percentage of dust in the test mixture.

M. Watteyne has made experiments on this point at Frameries, and has found that it has a very marked influence on the charge limite of explosives. In one case, with 38 per cent dust, the explosive fired the mixture with

A Paper read before the Royal Society of Arts, April 2, 1913.

200 grms., whilst it took over 600 grms. to fire it when there was only 10 per cent of dust; with another explosive the 38 per cent mixture was fired with 400 grms., and when the dust was reduced to 15 per cent it was not fired with over 700 grms.

At both Rotherham and Frameries the percentage of weight of dust to air in the gallery is approximately 10, but as the dust is raised by the explosive wave, the percentage present in the path of the outrush of heated products is probably far higher, and will vary probably with the kind of explosion. It is felt, however, that having the dust at rest resembles more nearly the conditions existing in a mine, where it is mostly raised by the explosion itself.

Great care is taken to allow time for the products of combustion from one shot to clear from the gallery before another test is made, as any products of combustion left would, by reducing the percentage of oxygen in the air, render the next test less sensitive.

At every testing station it has been recognised that the apparatus had its good and bad days, and that there were undoubtedly meteorological conditions which affected seriously the results of the testings, but what the interfering factors were has never been satisfactorily explained.

Early this year some experimental shots were fired at Rotherham with two explosives which proved thoroughly satisfactory, one failing to ignite gas or dust with a 32-02. charge, the other proving safe with 30 ozs., and as they were both stronger than most explosives that showed any promise of passing, the manufacturer was naturally elated, but decided wisely to have some more experimental shots fired with cartridges from the same batch before sending in the explosives for the official test. Both mornings were raw and cold, the explosives were the same batch, the dust freshly ground in each case, and the tests carried out under identical conditions, yet both explosives gave fierce ignition with small charges in dust, although the results in the gas mixture were the same as before.

The only difference between the two sets of experiments was that the first, when the explosives would have passed with the highest maximum charge, were carried out when there was an abnormally low pressure, the barometer standing at 29.3 ins., whilst the second set, in which both failed, were made with the barometer standing at 30 2. The difference of an inch in the barometric column makes a difference of about 3 per cent in the weight of the oxygen present in a cubic foot of air, and this is probably the factor that made the difference between passing the test with a 32-oz. maximum charge and firing the coaldust mixture with a small charge. I know that some authorities consider it is the volume and not the weight of oxygen in air that counts, but it seems to me that it must be the number of molecular contacts in a combining mixture that governs the rate and ease of combination; and if experience proves that pressure has this effect, what becomes of our tested safety when the explosives are used at the pressures existing in a deep mine? At any rate, if I may make the suggestion, it seems worth while to take advantage of all abnormal variations in pressure to see if any difference is noticeable in the sensitiveness of the coal-dust mixture when well-standardised explosives are fired into it, and, if this result is proved, to fix a barometric limit for days on which testings shall be made for the permitted list.

So far my criticisms-whatever they may be worthhave been directed to the conditions of the new tests, and now I want to call your attention to the nature and characteristics of the explosives that will be devised to enable them to pass for the permitted list.

The apparatus at Woolwich was altogether too small to obtain any definite information as to the alteration in "maximum charge" likely to be brought about by doing away with tamping; but some experiments have been made upon this point at Frameries which go to show that the wetter dynamites suffer the least, having the charge limite reduced only by one-half, whilst explosives con

AL NEWS

25, 19

(To be continued).

THE LATEST ACHIEVEMENTS AND PROBLEMS
OF THE CHEMICAL INDUSTRY.*
By CARL DUisberg.

PROBABLY in no domain of human knowledge and endeavour have the combined forces of theory and practice, intimately acting and reacting upon each other, made such immense strides and led to the solution of such difficult problems as in the Chemical Industry, an industry which, indeed, had its beginnings in the distant past, but in its vast development and international character is essentially a child of modern times. Success has so emboldened this industry that it considers itself capable of solving any problem, provided the men in its service are well trained in theory and practice, and ready to devote themselves to the best of their ability, with patience and perseverance, to the object in view. This has been shown by the struggle between the contact process of producing sulphuric acid and the old "chamber process," by the rivalry between the Solvay process and the Le Blanc method in the manufacture of soda; by the production of nitric acid and its salts by direct oxidation of nitrogen of the air under the influence of the heat of the electric discharge; by the manufacture of ammonia from atmospheric nitrogen indirectly via calcium cyanamide, and directly by combination with hydrogen; by the replacement of madder by alizarin, and of natural by synthetic indigo, as well as by innumerable other instances in the colour, perfume, and pharmaceutical industries.

If I venture before an audience not wholly consisting of chemists, within the brief period of an hour, to describe the latest achievements of the chemical industry and to recount the problems that are engaging our attention, I must restrict myself to a great extent both in the choice of the subject matter and its mode of presentation. We can, indeed, merely touch upon the most important happenings in our industry, and must from the very outset refrain from a thorough discussion of the subject, either from the purely chemical or the technical side. However, what cannot be described for lack of time, and what we should very much like to add for the sake of those chemists who are present, is illustrated by our rich collection of diagrams, products, and materials of all kinds. What can neither be mentioned in my paper nor illustrated by these exhibits will be demonstrated by means of lantern slides, and, should you possess patience enough, I shall show you at the conclusion of my address one of the newest factories which the German Chemical Industry has built on the

Rhine, with its various manufacturing departments, and, above all, its provisions for the welfare of its employees. In the spirit of Faust, "Who brings much will bring something to many," I invite you to make a flight with me in an airship, as it were, over the fields where the Chemical Industry holds sway, and, from our point of vantage, to take a bird's-eye view of the latest achieve. ments of this industry. Now and then, we shall make a landing and examine the most attractive features a little more closely. Production of Power.

The question of power, which is of the utmost importance in every industry, and especially in the great synthetic processes by means of which nitric acid and ammonia are manufactured, is now dominated by the perfected utilisation of hydraulic power and the development of the turbine. Not only does the transmission of electric energy render it possible to utilise water power at great distances, but it also permits the transmission of power evolved at the coal mines and the peat fields to distant points, thus eliminating the necessity of transporting the fuel itself. Recently, we also learned to apply the principles of the water turbine to the steam turbine. But this advance over the piston steam engine, which Watt so ingeniously constructed about 150 years ago, has already been surpassed by benzene, petroleum, or oil motors (Diesel motors), and, above all, by the reliable gas engines which are driven by blast furnace gases, Mond gas, and, more recently, by peat gas.

Production of By-products.

The manufacture of by-products goes hand-in-hand with this more direct generation of energy from fuel. These products include ammonium sulphate, of such great importance in agriculture, and the tar distillation products so indispensable in the colour industry. The latest and most rational method of utilising the peat or turf beds, so plentiful in Germany and in many other countries, is practised in Schweger Moor near Osnabrück according to a process discovered by Frank and Caro. There peat gas is produced and utilised and ammonia obtained as a byproduct, the required power being generated in a 3000 h.p. central electric power station. The moorland, after removal of the peat, is rendered serviceable for agricultural purposes.

At that place nearly 2500-2600 cubic metres of gas with 1000-1300 calories of heat were obtained from 1000 kg. of absolutely water-free peat in the form of airdried peat with 45 to 60 or 70 per cent of moisture. This gas represents energy equal to 1000 h.p. hours, equal to 700 kilowatt hours, after deducting the heat and power used for the operation of the gas works. In addition 35 kg. of ammonium sulphate were produced from the above quantity of peat which contains I per cent of nitrogen.

The greatest problem of power production, the direct conversion of coal into electric energy by means of gas batteries, a problem which we had hoped to solve twenty-five years ago, is still to-day nothing more than a dream.

Production of Cold.

Besides the problem of power and heat, the question of refrigeration is one of growing importance to the chemical industry. Instead of the ammonia machines with which a temperature of -20° C. can be attained, we employ to-day sulphurous acid machines, or, better still, resort to the carbonic acid gasifier, which yields a temperature of -40° C. It is hoped in the near future to produce refrigerating machines which, by the use of suitable hydrocarbons, will give temperatures of -80° C. Plants for the liquefaction of air, producing as low a temperature as -190° C., are becoming more and more common, and are especially profitable where gas mixtures, rich in oxygen, or where pure nitrogen, which is simultaneously produced, can be utilised. Diagrams showing the process invented