are uniform in composition throughout, whether prepared in sand or chill moulds.

The Effect of Small Quantities of Nickel upon High-grade Bearing Metal, by A. H. MUNDEY and C. C. BISSETT, B.A., B.Sc., B.MET.

This note gave an account of a practical trial of the effect of varying small quantities of nickel upon a tough and well-reputed bearing metal.

There was chosen for test the well known alloy consisting of:

Tin 93 per cent., Antimony 3.5 per cent., Copper 3.5 per cent.

The authors state that nickel is now found to be added to some considerable extent, possibly as a means of identification, but some merit is also claimed for it.

The results of the usual physical tests are detailed. Tensile, compression and hardness tests gave no indication of improvement due to the nickel in fact, the alloys were rather inferior when containing nickel. Running trials on the Thurston machine on strictly comparative lines showed practically no change as between nickel and non-nickel alloys.

The comparison of hardness at varying increased temperatures exhibited no improvement. Probably the most interesting feature is the structure as shown under the microscope. In the case of the alloy with no nickel the hard copper-tin constituent is very marked in its characteristic crystalline formation. The presence of nickel even in small quantities results in a great diminution of this crystalline structure, and the structure is only in a measure restored by the addition of more copper.

The authors conclude from their experiments that the beneficial results of nickel in alloys of the character employed are yet to be demonstrated.

The Measurement of the Change of Volume in Metals during Solidification, by HIKOZO ENDO.

In the casting process it is very important to know to what extent a change of volume occurs during solidification. Notwithstanding this great necessity, the literature concerning the phenomena is very scanty, because of the lack of a suitable method for arriving at an accurate determination. In 1888, Vincentini and Omodei calculated the change of volume of some fusible metals during solidification from the change of density at the melting point. The measurement of the density of different

metals in the vicinity of their melting points has been the subject of inquiry by several investigators among which are to be mentioned E. Wiedemann, Paul Pascal, and Louis Hackspill. M. Toepler, who studied the change of volume by means of a dilatometer, suggested a relation of the change of volume of a metal at melting point to its atomic weight, similar to that of the atomic volume to the atomic weight. Recently K. Bornemann and F. Sauerwald also measured the density of metals at various high temperatures by means of the Archimedes principle, using a mixture of sodium and potassium chlorides as liquid.

The present investigation was started in April, 1921, and the measurement of the change of volume during solidification or melting for a number of metals having low melting points up to 1100° C. has now been finished. This paper contains the results of the measurements, and forms the first report of the results of the investigation of a long series of experiments which are to be extended to other metals having higher melting points.

The method of investigation, which was suggested by Professor K. Honda, consists in the measurement of the change of buoyancy of a metal suspended in an inactive liquid during its solidification or melting by means of a thermobalance.

CORRESPONDENCE.

THE BRAILLE AND "SERVERS OF THE BLIND" LEAGUE.

To the Editors of THE CHEMICAL NEWS.

SIR,-As the President of the Braille and "Servers of the Blind" League, may I ask the sympathy of your readers for a unique work of help?

Up to the present no provision has been made for the defective blind childrenthose unfortunate babies who, in addition to blindness, have some other disability, such as backward mentality, deafness, dumbness.

The Braille and 'Servers of the Blind" League has undertaken to make this provision, and is establishing the Ellen Terry National Homes for Defective Blind Children, having purchased a home at Reigate, Surrey, where these little children, who are mentally and physically blind, will have the most skilful nursing and treatment, specially adapted educational facilities, and

training in trades suited to their varying capacities.

The Junior Home for children under seven is to do a splendid work, but money is badly needed to pay the mortgage and to obtain the necessary equipment. If funds are provided, the Home can be quickly enlarged to take in more than is at present possible.

Negotiations are taking place for additional homes in the north of England, but the scheme cannot be complete unless the public come to our aid.

Buildings exist in the grounds already purchased which can easily be adapted, if the money can be found for the alterations, for training defectives in light employment suited to their capacities.

The Ministry of Health gives the heartest welcome and support to our scheme, and is most anxious that we should bring it to an early fruition so as to extend it to the care of adult defectives. In addition, local authorities and blind institutions accord warmest co-operation to our plan, which fills a long-existing need. There is a constant enquiry regarding the admission of double defectives known to them.

No more deserving charity could be found. than the kindly care of these little onesborn into the world without light and without hope unless we come to their aiddoubly blind. May I ask for all who feel for these lonely babes-the parents and relatives of those children who are blessed with sight to share in a great national thank-offering for the power to see by sending their contribution to me at the address of the Braille and "Servers of the Blind" League, 3, Upper Woburn Place, W.C.1. Thanking you in the name of these little Yours sincerely, ELLEN TERRY.

ones,

New Patents.

HI8 list is specially compiled for The Chemical News, by Messrs. Rayner & Co., Registered Patent Agents, of 5. Chancery Lane, London, from whom all information relating to Patents. Trade Marks, and Designs can be obtained gratuitously. Latest Patent Applications. 21136-Cocksedge, H. E.-Manufacture of sodium carbonate. Aug. 21.

21072-Badische Anilin & Soda Fabrik.-Manufacture of formic acid. Aug. 20. Specifications Published this Week. 202078-Imison, C. S., Bligh, J. A., Wright, R. R., and Carmichael & Co., Ltd., J. F.-Furnaces producing sulphurous gases. Messrs. Rayner & Co. will obtain printed copies of the published specifications and abstract only, and forward on post free for the price of 1s. 6d. ⚫ach.

Associate, Institute of Chemistry.
F.I.C. in Chemical Engineering.

A number of Part-time Courses are also available to cover requirements of Work's Chemist, and those of those of various public examinations.

OPEN SCHOLARSHIPS, covering tuition fees and maintenance grants of £40 per annum for three years, are offered for competition annually, and candidates for entry to the above Department are eligible to compete.

For further particulars of Full-time and Part-time Courses, Entrance Examination, Scholarships, Fees, etc., apply to the Principal. Forms of application for admission to the Entrance Scholarship Examination, duly completed, must be received by the 17th September.

JOHN J. JACKSON,
Director of Education,

CITY HALL, CARDIFF.

It

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We must now look back again to the earlier stages of the present epoch in order to trace the development of our ideas on the detailed structure of the atom. That electrons as such were important constituents was clear by 1900, but little real progress followed until the part played by the positive charges was made clear. New light was thrown on this subject by examining the deviation of a particles when they passed through the atoms of matter. was found that occasionally a swift a particle was deflected from its rectilinear path through more than a right angle by an encounter with a single atom. In such a collision the laws of dynamics ordinarily apply, and the relation between the velocities of the colliding atoms before and after collision are exactly the same as if the two colliding particles are regarded as perfectly elastic spheres of minute dimensions. must, however, be borne in mind that in these atomic collisions there is no question of mechanical impacts such as we observe with ordinary matter. The reaction between the two particles occurs through the intermediary of the powerful electric fields. that surround them. Beautiful photographs illustrating the accuracy of these laws of collision between an a particle and an atom have been obtained by Messrs. Wilson, Blackett, and others, while Mr. Wilson has recently obtained many striking illustrations of collisions between two ↑ electrons. Remembering the great kinetic energy of the a particle, its deflection through a large angle in a single atomic encounter shows clearly that very intense deflecting forces exist inside the atom. seemed clear that electric fields of the required magnitude could be obtained only if

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the main charge of the atom were concentrated in a minute nucleus. From this arose the conception of the nuclear atom, now so well known, in which the heart of the atom is supposed to consist of a minute but massive nucleus, carrying a positive charge of electricity, and surrounded at a distance by the requisite number of electrons to form a neutral atom.

A detailed study of the scattering of a particles at different angles, by Geiger and Marsden, showed that the results were in close accord with this theory, and that the intense electric forces near the nucleus varied according to the ordinary inverse square law. In addition, the experiments allowed us to fix an upper limit for the dimensions of the nucleus. For a heavy atom like that of gold the radius of the nucleus, if supposed to be spherical, was less than one-thousandth of the radius of the complete atom surrounded by its electrons, and certainly less than 4 x 10-12 cms. All the atoms were found to show this nuclear structure, and an approximate estimate was made of the nuclear charge of different atoms. This type of nuclear atom, based on direct experimental evidence, possesses some very simple properties. It is obvious that the number of units of resultant positive charge in the nucleus fixes the number of the outer planetary electrons in the neutral atom. In addition, since these outer electrons are in some way held in equilibrium by the attractive forces from the nucleus, and, since we are confident from general physical and chemical evidence that all atoms of any one element are identical in their external structure, it is clear that their arrangement and motion. must be governed entirely by the magnitude of the nuclear charge. Since the ordinary chemical and physical properties are to be ascribed mainly to the configuration and motion of the outer electrons, it follows that the properties of an atom are defined by a whole number representing its nuclear charge. It thus becomes of great importance to determine the value of this nuclear charge for the atoms of all the elements.

Data obtained from the scattering of a particles, and also from the scattering of X-rays by light elements, indicated that the nuclear charge of an element was numerically equal to about half the atomic weight in terms of hydrogen. It was fairly clear from general evidence that the hydrogen nucleus had a charge one, and the