liquid, but is obtained as the fine dust called blue powder. Only with difficulty and by taking special precautions can this powder be caused to melt and to coalesce into liquid. consequently a second distillaand condensation usually is necessary to obtain the zinc in liquid form.

In an ordinary retort smelting plant 20 to 25 per cent. of the retorts are required continuously for the redistillation of blue powder, and from 25 to 35 per cent. of the total zinc produced is obtained from these retorts. In other words, in the primary distillation of zinc from its ores, about onethird of the zinc vapour condenses as blue powder, and only about two-thirds as liquid zinc.

All attempts at smelting zinc ores in a blast furnace have failed, because the zinc has always been obtained as a mixture of zinc oxide and blue powder.

The

Most of the electro-thermic processes that have been tried have also encountered this difficulty, and but few of them have succeeded in obtaining high yields of liquid zinc from the primary distillation. electric zinc-smelting works in Scandinavia, which are the only ones at present using an electro-thermic process on а commercial scale, have abandoned the effort to obtain liquid zinc from the first smelting operation. Formerly, they re-distilled the blue powder produced from the primary distillation of the ore, but in recent years have found that the powder can be melted by heating it to a temperature above the melting point and subjecting it to rubbing action.

American metallurgists who have experimented with electro-thermic processes have progressed somewhat further and a few have succeeded in obtaining satisfactory yields of liquid zinc in one operation. W.MCA. Johnson reports one furnace run in which 77.87 per cent. of the total zinc condensed was liquid. C. H. Fulton has said that no blue powder was formed during his experiments on a semi-commercial scale at East St. Louis in 1916 and 1917.

CAUSES OF BLUE-POWDER FORMATION. A detailed enumeration of all the causes of blue-powder formation includes so many physical and chemical factors that it is difficult to correlate them properly or to determine their relative importance, but the more important of them are quite generally recognised. They may be classified as physical causes and chemical causes, for the two act quite differently; the blue powder produced by physical causes and that produced by chemical causes have decidedly different characteristics.

PHYSICAL BLUE POWDER.

The production of physical blue powder is largely regulated by the design and temperature control of the condenser. When zinc vapour is condensed, that which condenses at temperatures above 419° C., is contained in the molten condition, either in drops or as a liquid body; that which condenses below 419° C. forms solid crystals similar to snow or frost. From a mixture of equal parts by volume of zinc and carbon monoxide,such as is produced in the reduction of zinc oxide by carbon, only a fraction of 1 per cent. of the zinc remains uncondensed at 419° C., so that it is theoretically possible to obtain nearly all of the zinc as liquid.

Most of the condensation normally takes place at the inner surface of the condenser walls, which, because they are continually radiating heat outward, are cooler than the vapour coming in contact with them. The zinc condenses upon this surface as liquid drops which increase in size until they coalesce and run to the bottom of the condenser to form a liquid bath. However, the zinc vapour must diffuse through the diluting carbon monoxide to come in contact with the condenser balls. This diffusion requires an appreciable time, and hence if the vapour is cooled too suddenly, or the distance through which the vapour must diffuse in order to reach the condenser walls is too great, the zinc will condense in the gas stream as minute droplets that will be carried along to the cooler region of the condenser and will solidify before they can coalesce. By cooling the vapour from a zinc retort very rapidly in a condenser that has a large ratio of volume to surface, all the zinc can be condensed as this " physical blue powder."

True physical blue powder is nearly pure zinc and contains very little zinc oxide or

other impurities. Its production is analogous to the production of flowers of sulphur, a chilled condenser being necessary. If heated under pressure in a reducing atmosphere, physical blue powder can be melted to liquid zinc.

CHEMICAL BLUE POWDER.

Chemical blue powder is caused by the formation of a solid film on the surface of newly-formed minute globules of liquid zinc as condensation progresses. The film prevents the globules from coalescing to larger liquid masses, even though the temperature conditions may be correct. This film may consist of zinc oxide, zinc sulphide, or similar zinc compounds caused by such gases as carbon dioxide, water vapour, or sulphur compounds formed in the retort, or by air diffused through the walls of the retort and condenser; or it may consist simply of fine dust carried over from the retort. Chemical blue powder usually contains considerable amounts of zinc oxide and smaller amounts of other impurities.

Of the detrimental gases that tend to cause the formation of chemical blue powder, carbon dioxide is most important. There are always small amounts of it in the gases that result from the reduction of zinc ores by carbon, and under certain conditions large amounts may be present.

CONDITIONS GIVING RISE TO CARBON DIOXIDE IN THE GASES RESULTING FROM THE REDUCTION OF ZINC ORES. Most metallurgists believe that the reduction of zinc oxide by carbon takes place in two stages:

ZnO+CO Zn+CO2

CO,+C=2CO

Both of these reactions are reversible and the direction in which each will proceed at any given temperature and pressure depends upon the relative proportions of zinc, vapour, carbon monoxide, and carbon dioxide present.

When the temperature of a charge of zinc oxide containing an excess of carbon is raised slowly and uniformly until the zinc begins to distil, the carbon dioxide formed at the lower temperatures is largely expelled or reduced to carbon monoxide, as the temperature increases, before any zine vapour is produced, and thereafter not more than a fraction of 1 per cent. of carbon dioxide can be formed in the presence

of the excess carbon. If, however, the charge is heated unevenly, so that part of it is hot enough to produce zinc vapour while other parts are cold enough for large amounts of carbon dioxide to be formed, the carbon dioxide and zinc vapour will enter the condenser together; the carbon dioxide will tend to oxidise the zinc and a large proportion of blue powder will be formed.

Some source of oxygen is, of course, required for this formation of carbon dioxide in the cooler parts of the charge. This source may be easily reducible oxides, such as those of lead and iron. Carbon dioxide may also be produced from carbonates introduced into the charge in uncalcined calamine ores.

Heating is especially liable to be uneven in electric furnaces that heat the charge by means of an arc or by the resistance of only a part of the charge, and is most detrimental in those processes in which the residue is melted to a liquid slag, because in those processes it is difficult to provide for an excess of carbon or sufficient contact of the gases with carbon.

Because of the influence of carbon dioxide on zinc condensation, quantitative information as to the amount of carbon dioxide necessary to oxidise zinc vapour in a mixture of zinc vapour, carbon monoxide, and carbon dioxide at various temperatures is of much practical value.

To obtain this information the investigation described in the present paper was undertaken by the Bureau of Mines, in cooperation with the Missouri School of Mines and Metallurgy, at the suggestion of C. H. Fulton,director of that school and consulting metallurgist of the Bureau of Mines. Doctor Fulton had already done some work on the equilibrium of the reaction Zn+CO2ZnO+CO, and the present investigation is to a certain extent a continuation of that work.

SUMMARY OF INVESTIGATIONS.

Because of the important effect of carbon dioxide on the condensation of zinc vapour in the metallurgical treatment of zinc ores, experiments were made to determine the concentration of carbon dioxide necessary to oxidise zinc vapour at various temperatures.

Although the preliminary experiments failed to give the quantitative information

desired, they proved that the required concentration of carbon dioxide increased with rising temperature. It was found that zinc oxide was reduced at 750° C. by carbon monoxide, even when carbon dioxide was present in large proportions, but that partial reoxidation took place in the cooler part of the reaction tube. The weight of zinc oxide reduced in a given time decreased with increasing ratios of carbon dioxide, and when 90 per cent. of carbon dioxide was present, the reduction and reoxidation was manifest only by a transfer of zinc oxide from the hot to the cooler part of the tube. It was furthermore found that all carbon dioxide was converted to carbon monoxide by reaction with zinc at some temperature between 750° C. and room temperature, if enough time were allowed for the completion of the reaction.

With the knowledge gained from these. preliminary experiments a final series of experiments was planned, from which the desired quantitative data were obtained.

These data were plotted and a curve drawn from which may be found the minimum concentration of carbon dioxide at any given temperature that will have an oxidising effect on zinc vapour under the conditions of zinc condensation in metallurgical practice.

It has also been demonstrated that the oxidation of zinc vapour by carbon monoxide is theoretically possible, though this oxidation is ordinarily of little practical importance.

General Notes.

COLLEGE OF TECHNOLOGY, MANCHESTER.

In a

This College has issued a comprehensive prospectus for the current session. prefatory note it is stated that the College has developed from the Manchester Mechanics' Institution, founded in 1824, in Cooper Street, until to-day it is of University rank and attracts students from all parts of the world. The Owens College, which was opened in Manchester in 1851, has grown into the Victoria University of Manchester. A Faculty of Technology in the University was established in 1905, with the Principal of the then School of Technology as Dean of the Faculty, and

with the heads of the Mechanical and Electrical Engineering, Applied Chemistry, and Architecture departments of the School of Technology as Professors of the University. The Department of Architecture is now confined to Owens College, and the head of the department of Textile Industries as a Professor of the University is now added to the Faculty, together with a number of the College lecturers who are also lecturers in the University. The Dean and the Professors are members of the University Senate. The University Courses provided by the College of Technology lead to the degrees of Bachelor and Master of Technical Science and Doctor of Philosophy (B.Sc.Tech., M.Sc.Tech., and Ph.D.).

II NATIONAL MEETING OF PURE AND APPLIED CHEMISTRY. PALERMO, MAY, 1926.

During the spring of this year, and exactly from 23 of May next to 2 of June, the Italian Association of Pure and Applied Chemistry (Rome) will hold in Palermo, the II National Meeting of Pure and Applied Chemistry.

On that occassion it will also celebrate the centenary of Stanislao Cannizzaro's birth.

Italy has already received many important adhesions that assure the greatest success to those functions.

Inquiries to Associazione Italiana di Chimica Generale ed Applicata; Roma 1Via IV Novembre 154.

FRANKLYN INSTITUTE.

JOHN PRICE WETHERILL SILVER MEDALS. The Franklyn Institute gives notice that they intend to award the above to Dr. Frank Twyman, of London (England), for his Hilger Interferometer, and also to Wagner Electric Corporation, with special mention of Val A. Fynn H. Weichsel, for their Fynn-Weichsel motor.

BRITISH IRON AND STEEL OUTPUT.

Production of pig iron in the United Kingdom during January, at 533,500 tons, compares with 503,400 tons in December, and was the largest since the May, 1925, output of 574,700 tons. The production of steel ingots and castings was also above that of the previous month, but below the output of November and the two preceding months.

SOIL.

The purpose of the B.D.H. Soil Testing Outfit is to enable farmers and all persons interested in agriculture and horticulture to determine the "reaction" of the soil with rapidity and ease. By means of this outfit it is possible to find out in a few moments whether a given soil requires treatment with lime in order to remove sourness and to ensure healthy crops and better production.

The B.D.H. Soil Testing Outfit affords a simple means by which the farmer can determine the state of his soil wherever and whenever he wishes to do so, without the need of any knowledge of chemistry.

DESCRIPTION OF THE OUTFIT.

The outfit is designed for actual use in the field, and consists essentially of a dropping bottle containing the B.D.H. Soil Indicator, and a specially designed porcelain boat which is divided by a partition into two unequal parts. One end of the boat is used for mixing the sample of soil with the indicator, and the smaller end for the reception of the coloured liquid which is drained off from the mixture. In addition, a small spatula is supplied for handling the soil, and mixing it with the indicator.

A sufficiency of lime in the soil is shown. by the liquid remaining green, while if an abundance of lime is present, and the soil is actually alkaline, the liquid turns blue.

METHOD OF CARRYING OUT THE TEST. Using the small spatula provided, the larger end of the porcelain boat should be about three-quarters filled with the soil to be tested. The B.D.H. Soil Indicator should then be added drop by drop to the soil until it is thoroughly wet and the indicator just covers the surface. At this stage the end of the boat containing the mixture of soil and indicator should be titltd slightly downwards in order to prevent the liquid from running into the smaller end. The wet soil should next be stirred gently but thoroughly with the spatula, the soil should be allowed to settle for a few seconds, and the boat should then be titled gently in the opposite direction, so that the surplus liquid will flow into the small well, where the colour may be observed readily.

A red colour indicates a very acid soil. An orange or yellow colour indicates an acid soil.

A green colour indicates a neutral soil. A blue colour indicates an alkaline soil. The B.D.H. Soil Testing Outfit, complete with special porcelain boat, spatula, and a bottle of the B.D.H. Soil Indicator in card box, price 4s. 6d.

Spare bottles of B.D.H. Soil Indicator2s. 6d. each.

Spare porcelain boats-1s. 9d. each.
Spare spatulas-6d. each.

The B.D.H. Soil Testing Outfit may be obtained through Chemists and Druggists, or through any dealers in chemicals and scientific instruments ,or direct from the sole manufacturers The British Drug Houses, Ltd., Makers of Fine Chemicals, Graham Street, City Road, London, N.1.

PROCEEDINGS AND NOTICES OF SOCIETIES.

THE ROYAL SOCIETY.

At the meeting held on January 28, 1926, the following papers were read:

The Cretaceous Plant-Bearing Rocks of Western Greenland. By A. C. SEward, F.R.S.

In 1921 the author, with financial assistance from the Royal Society's Covernment Grant and the Worts Fund (Cambridge), spent rather more than two months in Western Greenland, collecting fossil plants; he was accompanied by Mr. R. E. Holttum, who ably assisted him and made large collections of recent plants. The present paper deals briefly with the geology of the localities visited, and, more fully, with the plants collected the coasts of the Núgssauk Peninsula, and on the south-east coast of Disko Island. The fossils obtained include many species previously described by Heer, most of whose type-specimens have been examined in the museums of Copenhagen and Stockholm, and compared with the illustrations in the Flora Fossilis Arctica.

on

mined during growth in length. Genetic and ordinary environmental influences do not affect the statistical peculiarities of the reversals. The final adult length of the hair and the time taken in reaching that length do affect the reversal distribution.

Nearly all the seed hairs of Gossypium begin to grow on a sinistral spiral, i.e., the opposite hand to an ordinary screw thread. This basal sinistral spiral increases in length, is broken up, and later additions may be made to its fragments. Similar extension, fragmentation, and subsequent addition take place with the later dextral spiral.

The angle of the helix varies somewhat around two modal values, viz., approximately 27. and 27. sinister. The local variations of the angular value are quite unaffected by inversion of the hand of the angle from dexter to sinister.

66

Dexter and sinister wall structures have been found in some hairs to have different structural properties in their resistance to collapse after the death of the cell. A tentative explanation of the causation of reversal is suggested; but attention directed to its insufficiency and to the need for experimental evidence.

is

A Contribution to the Anatomy of the Ductless Glands and the Lymphatic System of the Angler Fish (Lophius Piscatorius). By R. H. BURNE. Communicated by Sir Arthur Keith, F.R.S.

This paper deals with the thymus and thyroid bodies, and a system of "fine" lymph vessels with the structure of arteries.

1. The thymus body is not of the placodal type normal to Telecosts, but lies free beneath the mucous membrane of the pharynx, connected with the branchial cavity by a tube. This tube is not a duct, but more nearly resembles the crypts characteristic of the Mammalian tonsil. Its epithelium is similar to that of the pharynx and passes by transitional stages into the reticulum of the thymic lobules.

2. The thyroid body is occupied by a large lymph sinus, into which lymph passes through valved openings from ventral and branchial lymphatics, and from which it is conveyed to the heart by the inferior jugular. This vein is devoid of its normal factors and serves simply as a lymph channel. The majority of the thyroid vesicles project into the lymph sinus being separated from containing lymph by endothelium only.

3. Distributed to mucous membrane of mouth and pharynx, and to skin of forepart of body, is a system of "" fine " vessels, similar in structure to small arteries. These vessels are not part of the blood vascular system, but connect by their terminal branches with the ordinary lymphatics. In mucous membranes these connectives are valved, to direct through them a flow from the lymphatic capillary network. Connections between the terminals of the two systems in the skin are apparently not valved. The "fine" vessels contain blood or lymph, the flow of which seems to be from mucous membrane to skin and to walls of hypobranchial and other arteries. They are probably an afferent system of lymphatics, the terminal branches of which were observed in action in the fins of young Flat-fish by Jourdain.

The Development of the Calcereous Test of Echinus miliaris. By I. GORDON. Communicated by Prof. E. W. MacBride, F.R.S.

All elements of the permanent skeleton which are laid down in the larva are traced back to a single spherical granule. This granule, with two exceptions, becomes a triradiate spicule even in the formation of a tetraradiate spine. The exceptions are in the development of (a) the base of a typical Echinoid spine where it becomes hexagonal (a modification of the triradiate symmetry), and (b) the component parts of a tooth. The development of the tetraradiate spine, the simple and the compound tube-feet discs, and the blade of a pedicellaria is new.

A suggestion as to the origin of the unusual symmetry of the tetraradiate spines is put forward and the relationship of (a) the sphæridium and (b) the pedicellaria blade to a typical spine discussed. In the post-larval development the formation of an echinoid" triad is described, together with the changes it undergoes after its inception and the displacement of the podia (pore-pairs) from a uniserial to a triserial arrangement.

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Regarding the question of "plate crushing" and resorption two phases occur, one in which resorption at the peristomial margin is fairly rapid and "plate-crushing " slow, one in which the opposite is the case, resorption at the margin practically ceasing. The second phase occurs after the completion of the perignathic girdle. The large buccal plates arise interradially, and there