twenty-four millions. On the other hand, the Lake of Geneva contains one part of ferric oxide in about three million, but the water is blue and not yellow. The water of the Meuse is green and not yellow when it contains one part of ferric oxide in 1,500,000 of water. On the basis of analysis the Mediterranean should be brownish-yellow and not blue. From this it follows that the iron in these waters is not present in the same state as when a solution is made up in the laboratory. The point that has been overlooked is the effect of humie matter.

.

"In order to get suitable humic matter I have taken the black waters from the peat bog on the plateau of Baraque Michel, which is the highest plateau in Belgium. In this way I was certain of getting water uncontaminated by industrial products and containing only the brown-black compounds dissolved from the peat. It is therefore probable that the substances used corresponded closely and perhaps absolutely with the humic matter found in so-called pure, natural waters. In fact the water I used was as black as ink by reflected light but somewhat coffee brown by transmitted light when observed in a twentycentimetre layer. It can be filtered through filter paper, though very slowly, which proves that the brown substance is not entirely in solution. Its density was o'99885 at 25.5°. Since pure water has a density at o 99759 the peat water was 1'0012 times as dense. When examined with a spectroscope it gave a continuous, dark spectrum, in which one saw only red and green, but no blue and almost no yellow. It had a slight acid reaction. When evaporated in a platinum crucible, it left a black residue of o 152 grm. per litre. After the carbonaceous matter had been destroyed by beating in the air the residue weighed 0.0238 grm. There was therefore o 1282 grm. of organic combustible matter per litre of water. The small content of mineral matter (0.0238 grm./litre) indicated a water that has not flowed far through the earth. It is actually rain-water filtered slowly through a layer of peat. "With this peat water the effect of humic matter on the colour of water has been determined. The data are given in Table VI., the concentrations being grms. of combustible matter per grm. of water.

"This table shows the extreme colouring power of bumic matter. It has an effect about double that of ferric oxide if one compares equal weights. It is therefore easy to see the difficulties to be surmounted in a laboratory preparation of a really blue water, a pure water not containing more than one part in fifty million of organic matter.

"Filtered water from the Meuse contains about I grm. of combustible matter in nine thousand of water. If the combustible matter in the water of the Meuse were brown, soluble, humic material like that of the peat water, the river should look like a river of ink. The organic matter of the natural waters can no more be dissolved humic matter than the ferric compounds can be in a true state of solution. The concentration is more than a thousand times that which corresponds to the actual colour of the

249

ferrous compounds, the colouring effect of which is not comparable with that of the ferric compounds. Owing to the absorbed oxygen the humic matter probably becomes more acid, and therefore forms salts more readily with the oxides of iron, alumina, &c., these [hypothetical] salts precipitating readily on account of their insolubility. The ferrous compounds remaining in solution are oxidised by the action of the air or by the oxygen dissolved in the water. When converted into ferric compounds they oxidise more of the unprecipitated organic matter. The ferric compounds therefore act in natural waters in the way hæmoglobin does in the blood of animals. Hemoglobin is looked upon as an oxygen carrier, taking it up from the lungs and distributing it through the system. The organic substances in the water are immersed in a medium which burns them while the body of an animal is irrigated by an oxidising liquid.

"The interaction of ferric salts and organic substances under the influence of light gives rise to an apparent equilibrium between the oxygen of the air and the ferrous compounds. If the intensity of the light increases, the proportion of ferric compounds decreases, because the organic substances will be oxidised more completely. Since the water will then contain smaller amounts of yellow or brown compounds, it will become more and more distinctly blue. On the other hand, if the intensity of the light decreases, the rate of the oxidation will decrease and the water will become more and more green, or even yellow, because the supply of colouring matter will not fall off with decreasing intensity of light. It is therefore easy to see why waters exposed to the sun, arc usually the bluest.

"If the amount of iron is very small relatively to that of the humic substances, these latter may be oxidised very slowly, in which case they will impart their brown, or even black, tint to the waters in which they are. The black waters of the equatorial regions of South America are said to contain 0.028 grm. of free humic acids per litre (Muntz and Marcano, Comptes Rendus, 1888, cvii., 231), a little more than one-fifth as much as the black peat water from the plateau of Baraque Michel in Belgium. In his paper on the colour of water, Wittstein (Vierteljahresschrift Prakt. Pharmacie, 1861, x., 346) bas pointed out that the brown waters of Bavaria are remark able for their softness. They contain almost no mineral matter.

"If the amount of iron is relatively large, there may be almost complete elimination of the organic matter. Almen (Ber., 1871, iv., 750) has called attention to the purity of the great lakes of Sweden. Lake Wettern is almost free from organic matter. Between these extremes there are the more common cases where the waters contain iron and organic substances in what one may call ordinary amounts. If one omits the instances where these waters are obviously turbid, their colour will be a dark green like those of most of our rivers, the Meuse, for instance, the waters of which are characterised by the absence of depth of colour and by a lack of that transparency which one finds in lakes or in the ocean. This is the effect that would be produced by the joint presence of iron and of organic substances.

"In so far as the waters of the river are exposed to the sunlight, a purification is continually taking place. If the river is sufficiently long the purification may even be com plete before the waters reach the sea. This happens with the Nile. The upper waters are green in the dry season and become more and more blue as one approaches the mouth of the river. In this case one can exclude the hypothesis of the change of colour being due to the influx of other waters. It is the water of the Nile itself which changes colour as it flows to the sea.

"In this way one can account for the deep blue colour of the high seas and in general of large masses of water, even when the analysis does not permit us to recognise any important differences. The ease with which humic matters combine with ferric oxide makes it clear why fer

ruginous mineral deposits always contain organic matter. In fact, the limonites of the prairies and the ochres have been suggested as raw material for making humic com pounds.

The green often observed in swimming pools is undoubtedly due to suspended matter, though I can find no record of anybody having determined the exact nature of the suspended matter.

A special point has been discussed by Steuer (Zoologische Jahrbücher, Abth. fur Systematik, Geographie und Biologie der Thiere, 1902, xv., 7). "The colour and the transparency of the water of the Danube bear so close a relation one to the other that we cannot treat them separately. We may draw the following general conclusions:-In winter the water is usually turbid and green to yellowish green; the melting snow and ice in the spring with the consequent rise of level, together with the influence of the drainage water, increase the turbidity and make the colour of the river even more yellow. That the colour of the Danube never is blue except in the song is well known. At best the water is greenish, and usually it is a dirty yellow. On the other hand, after a few windless days in late autumn, winter, and occasionally in spring, the water of the old Danube' become quite clear and appears a beautiful blue. Apart from the presence of plankton, the transparency and change of colour of the water vary with the suspended particles of sand or mud which are removed from the shore or the low islands by strong winds or high waves; are carried in by drainage water from the ground and also from the right bank; or are brought down by the melting snows in the spring." The work of Aitken and Spring would seem to have settled the whole question were it not that Lord Rayleigh has recently brought the matter up again (Nature, 1910, lxxxiii., 48; Scientific Papers, 1912. v., 540). "A recent voyage around Africa recalled my attention to interesting problems connected with the colour of the sea. They are not always easy of solution in consequence of the circumstance that there are several possible sources of colour whose action would be much in the same direction.

BOARD OF TRADE ANNOUNCEMENTS.

EXPORT OF COAL.

IN conformity with the policy of relaxing controls and facilitating the return to normal conditions. certain changes have recently been made in the conditions affecting the sale of coal for export, and it is now proposed, inter alia, to terminate the system of limited prices at present in operation in the case of coal shipped to France, Italy, and other Allied countries.

IMPORT RESTRICTIONS

The Board of Trade notify that general licences have articles:-Cocoa butter; oleo stearine; olive oil; fruit been issued permitting the importation of the following (fresh), except pears and grapes; articles of food containing sugar; aerated mineral and table waters (sweetened); gherkins in brine.

NOTES.

ROYAL INSTITUTION.-Next Tuesday, May 27, at j o'clock, Prof. W. H. Bragg will deliver the first of two lectures at the Royal Institution on "Listening Under Water" (the Tyndall Lecture). On Thursday, May 29, at 3 o'clock, Sir Valentine Chirol will give the first of two lectures on "The Balkans." The Friday Evening Discourse, on May 30, at 5.30 o'clock, will be delivered by Sir John Rose Bradford on "A Filter-passing' Virus in Certain Diseases." The closing Discourse of the Ses. sion will be given on June 6 by Prof. Sir Ernest Ruther ford on "Atomic Projectiles and their Collisions with Light Atoms." On Saturday, May 31, at 3 o'clock, Mr. J. M. Price will give the first of two lectures on "The Italian Front," illustrated by cinematograph films lent by the Italian Government.

We must bear in mind that the absorption, or proper, colour of water cannot manifest itself unless the light traverse a sufficient thickness before reaching the eye. In the ocean the depth is of course adequate to develop the colour, but if the water is clear there is often nothing to send the light back to the observer. Under these circumstances the proper colour cannot be seen. The much admired dark blue of the deep sea has nothing to do with the colour of water, but is simply the blue of the sky seen by reflection. When the heavens are overcast the water looks grey and leaden; and even when the clouding is partial, the sea appears grey under the clouds, though elsewhere it may show colour. It is remarkable that a fact so easy of observation is unknown to many even of those who have written from a scientific point of view. One circumstance which may raise doubts is that the blue of the deep sea often looks purer and fuller than that of the sky. I think the explanation is that we are apt to make comparison with that part of the sky which lies near the horizon, whereas the best blue comes from near the zenith. In fact, when the water is smooth and the angle of observation such as to reflect the low sky, the apparent blue of the water is much deteriorated. Under these circum. -stances a rippling due to wind greatly enhances the colour by reflecting light from higher up. Seen from the deck of a steamer, those parts of the wave which slope towards the observer show the best colour for a like reason.

(To be continued).

A VALUABLE deposit of manganese has recently been discovered in Ecuador, near the town of San Antonio, in the province of Pichincha, South America. The deposit consists of a vein from 3 to.9 feet thick. The ore assays about 50 per cent manganese with silica and iron.

EYE PROTECTION in Welding OPERATIONS. The ideal

goggle for use in welding is that which permits of greatest visibility, and at the same time excludes heat rays and ultra-violet rays. The author shows the spectra of a number of commercially available glasses and combinations of glasses, and explains bow such spectra may be used to discriminate between various filters. The selection of coloured glasses to yield clearest definition with sufficient obscuration of glare is necessary where there are powerful visible rays. This selection is a matter for experts. absorbing glass may be necessary. Clear glass (but not quartz or natural rock crystal) is a protection against ultra-violet rays which are not too intense. Dark amber or dark amber green glasses are an absolute filter for ultra-violet rays; glasses showing blue or violet tints should be avoided unless they are needed to obscure other colours.--(W. S. Andrews, General Electric Review, Dec., 1918).-Technical Supplement.

In addition heat

Ar the recent meeting of the Faraday Society and the Röntgen Society, Sir Robert Hadfield and Mr. S. A. Main gave an account of the results of the X-ray examination of the carbon electrodes used in steel making furnaces. These electrodes vary in size and reach no less than 20 inches in diameter; if during a melt portions fall into the steel bath the whole cast may become spoilt or wasted. Sections were cut about 1 inch in diameter and submitted to X-ray examination, and the results, which were of course of a preliminary nature, do not appear to have been very encouraging. Where a uniform structure was noticed in the radiograph the "service quality" of the electrode is reported as "fairly good," while another electrode that gave by X-ray examination a coar-e structure very full of opaque grains gave in service an excellent result. Faults in manufacture such as cracks and flaws are, of course. revealed. Further work on the subject will probably yield valuable results.

CHEMICAL NEWS, May 23, 1919

A NOVEL form of CO2 indicator has recently been evolved that presents several new features, the chief being its extreme simplicity; there is no complicated mechanism to get out of order, and the percentage of CO, is read by the height of a column of water. The instrument can be fixed in the stokehold so that the fireman can see at a glance what is taking place in the turnace. The indications are said to be accurate to within I per cent. A list of representative purchasers shows that it is being used by most of the prominent firms in the country. Full particulars can be obtained from W.R. Patents, Ltd., 8, Oid Jewry, London, E.C.

THE International Institute of Agriculture publishes a note on the "Extent of Land under Winter Crops of Cereals and Oil-seeds in the Northern Hemisphere," and it is stated that the area under wheat in the United States has been increased by 16 per cent as compared with that of last year, while, for every country except this, there appears a decided decrease in the wheat areas even amounting to a very large decline in the case of British India. As regards the crop condition on April 1 it is reported as a good one for wheat in the United States and for oats in Ireland. It is classed as satisfactory for wheat in England and Wales. In Italy, as well as for crops in general, the condition was an average one at the date named, while in Scotland the wheat was reported as below the average in condition.

THE demand for "power" for the manufacture of munitions, combined with the world shortage of coal, has made it necessary to systematical y survey the available water power in various parts of Europe. The second report of the Water-power Committee of the Conjoint Board of Scientific Societies has just been published. Surveys of the water power available in India, Africa, and the Colonies are being made, and all the information collected. The probable outcome of this work will be the employment of a deal of power to useful purposes instead of allowing it to be wasted. Much has been done in this direction in Germany and Austria during the war. Water power in France is being applied largely to the electrification of railways. In Great Britain and Ireland the present total developed power is 210,000 B.H.P. The discovery of large deposits of bauxite in British Guiana and the fact that much water-power is available in the locality gives good prospect of this colony becoming an important producer of aluminium. It is recored that one river alone offers the possibility of two and a half million B.H.P. In Rhodesia the estimated power at Victoria Falls at low water is 350,000 B.H.P.; at flood power this would be greatly exceeded. The report concludes by pointing out the necessity for training engineers to undertake the work, and the Committee recommends that the matter be brought to the notice of the Minister of Education and the Secretary for Scotland.

NOTES FROM FOREIGN SOURCES

Spectrographic Study of the Ash of Marine Plants. -Eugène Cornec.—It is known that a very large number of elements are to be found in traces in sea water, and it seems probable that the selective power of marine plants is not limited to iodine, so that the ash of them should contain many elements. The author has subjected the ash of such plants, after extraction with water and hydrochloric acid, and also the precipitates corresponding to the different analytical groups, to spectrographic examination, the complete study of the spectrograms being limited to the ultraviolet region comprised between 2500 and 3500 A.U. Without being absolutely general the method is applicable for most of the heavy metals, and specially for the rare metals. He has thus detected the presence of metals, which he has classed together in three groups.

251

In the first group he includes those which are already known to exist in marine plants, such as silver, arsenic, eobalt, copper, &c. The second group contains those which have been detected in sea water-bismuth, tin, gallium, molybdenum, gold; while the third group con. sists of such elements as have not been found either in sea water or in marine plants. These are antimony, germanium, beryllium, titanium, tungsten, and vanadium. There are no indications of the presence of elements of the platinum group, nor of those of the rare earths. The absence of thailium and indium is specially noteworthy. Gold, bismuth, gallium, and germanium exist only in spectrographic traces.-Comptes Rendus, 1919, clxviii., 513.

Evolution of Gas when Fused Sodium Hydroxide is Dissolved in Water.-W. H. Schramm.-It has tre quently been observed that when fused sodium hydroxide is dissolved in water a gas of piercing odour is evolved. The author has shown that this effect is produced by the action of a very small quantity of oxygen which is set free by the decomposition of a chemical compound and escapes mixed with air. The compound in question is an alkali compound of a higher oxidation product of iron, possibly sodium perferrite, Fe204. Na2O. - Chemiker Zeitung, 1919, xliii., 69.

Determination of Sulphuric Acid and Sulphates.M. G. Meilière.-Two chiet causes of error in the quanti tative determination of SO4 as BaSO4 are due to the energy with which the precipitate and the filter-paper both retain the excess of barium salt used as precipitant by a phenomenon of adsorption. The separation and washing of the precipitate by centrifugation, weighing the sulphate in the tube itself, does away with one of these errors but not the other. The washings can be much bastened by working in a solution acidified with a little acetic acid at a temperature as near 100° as possible. A double filter must be used and gentle suction must be employed. To avoid the use of too much barium salt in the case of the determination of H2SO4, baryta water may be used and a trace of phenolphthalein may be added; the coloration should persist some minutes after the addition of baryta water. Then the liquid must be acidified with acetic acid, kept on the water-bath for and hour or two, and then filtered.

Existence of Isotungstic Acid.-P. Barbe.-In 1847 Lanreut described an isotungstic acid, which G rber also obtained and investigated in 1917. When metatungstic acid was boiled with excess of ammonia, or when an ammoniacal solution of certain purified tungstic acids was evaporated, ammonium isotungstate was said to be formed. When calcined it gave a dark green or even black tungstic anhydride of composition 6Wo03.2(NH4)2O.7H2O, which gave for the value of W O 3 30, whereas the value for a paratungstate would

(NH4)20

be 2.3 to 2.4. Isotungstic acid, when reduced by hydrogen, gave a crystalline metallic product, and the atomic weight of the metal appeared to be 187, or three units more than the officially recognised number, Gerber concluded that isotungstic acid contains, besides tungsten, a new substance of higher atomic weight, which he called neotungsten, but this result was not confirmed by spectroscopy. The author has repeated the experiments, preparing the isotungstate by three different methods and determining the ratio of WoO3 to (NH4)2O in each case. He finds that the presence of sodium raises the value of the ratio from 24 to 3'0, and at the same time accounts for the other characteristic properties of isotungstic anhydride, including the dark green colour. Thus the substance which Gerber called ammonium isotungstate is really a double tungstate of ammonia and soda, and the author believes that there is no real reason for suggesting the existence of another tungsten of higher atomic weight than that officially recognised-Moniteur Scientifique, 1919, 73.

CORRESPONDENCE.

ANALYTICAL EXAMINATION OF ACORNS AND HORSE CHESNUTS.

To the Editor of the Chemical News. SIR,-In the CHEMICAL NEWS, cxvi., 244 (Nov. 16, 1917), there occurs an abstract of a paper on this subject by J. L. Baker and H. F. E. Hulton, in which it is stated that no diastase occurs in the acorn either before or after germination. On p. 177 of "The Principles and Practice of Brewing" (W. J. Sykes, 1897) it is stated:-"Hops, like all other plants, contain diastase, but this point appears to have been overlooked until attention was called to the fact by Brown and Morris (Fourn. Federated Inst. Brewing, 1897, p. 233). The enzyme could only be extracted by water after removal of the tannin contained in the bops. A similar phenomenon was observed by Baranetzky with reference to acorns (Sachsse, "Agri. culturchemie," p. 364).

If a plant does not contain diastase, what enzyme does it contain which converts starch into soluble carbo bydrates? I am, &c.,

30, Albert Street, Shrewsbury.

CHARLES E. FRANCK, A.I.C.

Tuesday, May 27.

Royal Institution, 3. "Listening under Water," by Prof. W. H. Bragg.

Institution of Gas Engineers, 10.30 a.m. Royal Horticultural Society, 3. "Some Irish Gardens," by J. G. Weston.

Institution of Electrical Engineers, 6.30. (At Caxton

Hall, Westminster). Discussion-Electrical and Engineering Equipment of Modern Small Houses. Royal Photographic Society, 7. "Spiders-Their Structure and Habits," by Dr. G. H. Rodman. Royal Society of Arts, 4.30. "Science and Industry in Australia," by Lieut.-Colonel the Hon. Sir John McCall.

Wednesday, May 28.

Institution of Gas Engineers, 10.30 am.

Analytical Chemist wanted. Must be fully

trained and have good general Analytical experience. Applica tions must contain full particulars of age, training, experience, and salary required, and must be made in writing to General Works Manager, Messrs Lever Brothers Limited, Port Sunlight, Cheshire.

Chemist, demobilised, three years' Technical

College training and one year works experience, in order to regain experience, lost Army service, would communicate with Analyst period.-Address, R. B., CHEMICAL NEWS Office, 16, Newcastle of extensive practice with view to Post as Pupil Assistant for limited Street, Farringdon Street, London, E.C.4.

Chemist desires Employment in London. years Organic Research Work. Would be content to start as Assistant in any branch of Chemistry.--Address, S. L., CHEMICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. 4.

During War, Chief Chemist in a Canadian T.N.T. plant. Two

Chemist, with four years' training at Finsbury

Technical College, having taken active service immediately upon completion of course, is now demobilised and seeks Engagement. - Address, A. E. G., 21, Chestnut Road, West Norwood, S.E.

Assistant Chemist wanted for the Fuel

Research Laboratory. One preferred with B. Sc. Degree, but not absolutely essential. Should have good knowledge of Geology and Palæobota y. State particulars of training and experience, age, and salary required.-Address, F. R., CHEMICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. 4.

RESEARCH-Repatriated prisoner, honours

graduate, Physical, especially Electro-chemistry and Physics, 17 years in practice, record of successful inventions, experience in organising and running manufacture in England and Germany, before war practising consultant, seeks suitable position.-Address, R. R., CHEMICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. 4.

Student, finishing four year Associate Course

in Applied Chemistry in June next, desires to communicate with firms re suitable appointment, Foreign or Colonial post desirable.Address, Student," CHEMICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. 4.

"How to Start and

Succeed in General Practice," by Dr. Steele-Perkins

Friday, May 30.

OFFERS

WANTED

VEGETABLE OILS,
TAR PRODUCTS,
LINSEED OIL,
CHEMICALS,

ARTIFICIAL MANURE.

Particulars, with Samples, to

IN

HOLYER NIELSEN and CO., FREDERICKS BOrggarde 34, COPENHAQSN, DENMARK,

SCIENTIFIC BOOKS AND SERIALS.

Institution of Mechanical Engineers, 6.

Institute of Chemistry, 4.30. (Council Meeting).

Saturday, May 13.

Books in all departments of Science and Natural History, also Transactions and Journals of Learned Societies, &c., in sets, runs, and single volumes or numbers.

LIBRARIES or SMALL PARCELS PURCHASED. SPECIAL CATALOGUES-Chemical, Botanical, Zoological, Ornithological, Entomological, Geological, &c.—2d. each post free.

Price.

Telephone-Gerrard 1412.