82

Chemical Notices from Foreign Sources.

glass or porcelain tubes, and was enabled to perform combustion after combustion with the greatest ease."

Before applying the platinum tube to the direct combustion of iron or steel," an experiment was tried with pure sugar to ascertain whether a stream of oxygen, in conjunction with a layer of only 4 inches of cupric oxide would be sufficient to convert all the carbon into carbonic anhydride. The result was perfectly satisfactory, an amount of carbonic anhydride being obtained equal to 42'086 per cent of carbon instead of 42'105, showing a loss of only o'o19 per cent upon the theoretical amount." To prove that a platinum tube is equally applicable in the case of small quantities, I give the results of duplicate estimations of carbon in steel by direct combustion:

5.
1.180 o'921 0'763
0.649
0'359
I'151 0'922 0'759 0.620 0*359
0'758

The expense of platinum tubes has probably millitated
most against their general use, but where a number of
analyses has to be made this would soon be compensated
for by the saving of time and glass tubes.—I am, &c.,
W. DOUGLAS HERMAN.

Cropper's Hill, St. Helens, Lancashire,

August 21, 1876.

{CHEMICAL NEWS,

August 25, 1876.

| nitrogen, Berzelius adds "Il semblerait, d'après cela, que le degagement d'oxygene dans ces animaux est du à traction du soleil sur la chlorophylle qu'ils contiennent," a singularly sagacious conclusion, and one that ought to induce those interested in water-supply to have this matter thoroughly investigated by competent individuals, for it is quite possible that the growing of water-cresses, for instance, and the purification of water are more nearly related to each other than directors of water companies imagine.

That chlorophyll performs important duties in both the vegetable and animal economy seems certain, though its powers as yet are undefined and but little understood. Still, however, we can notice that it invariably exists on the surface of the living leaves of plants, also in the bile, and sometimes in the blood of animals; and within the last two years it has been discovered that the spots and colouring found upon the eggs of birds is chlorophyll; and, in some cases, as in the egg of the hedge-sparrow, this chlorophyll is blue (which seems, indeed, to be the colour of pure chlorophyll, as will be explained on a subsequent occasion, when speaking of the composition of bile, a matter now under examination). For the present we may remark that room enough exists to warrant energetic interference on the part of our Metropolitan water directors with the closely-allied subjects of water-purity and water-jobbery; because it may so be that Nature's

THE PRESENCE OF NITRITES IN THE WATER remedy is staring them in the face whilst they are blindly

OF THE THAMES.

hunting by expensive methods to perform a really inexpensive operation, and thus uselessly sinking an immense capital that will have to be paid for hereafter, and To the Editor of the Chemical News. therefore in all time to come limit the use of Heaven's SIR,-The following experiments were made with a view greatest boon throughout the largest metropolis in the to ascertain whether nitrites of any kind existed in Thames world. We have already seen something of this kind water; but although the process employed was one brought about in the case of coal-gas, the price of which capable of detecting the ten-thousandth part of a grain of in London at the present moment would not have been any nitrite whatever, yet it totally failed in this instance more than two shillings per 1000 cubic feet had matters to indicate even a trace. The first experiment was made been left to the wholesome action of common sense and upon Thames water which had been purposely allowed to honest competition. But all the benefits arising from imconcentrate in a steam-boiler until 400 cubic feet of it had provements and economies in gas-making during the last been reduced to 8 cubic feet, and of this concentrated twenty years has been swallowed up by expensive Acts of water I gallon was evaporated down to the bulk of 100 Parliament and engineering jobbery, so that the price grains, when it was tested in this manner :-One drop of | remains almost unchanged, and is, perhaps, unchangeable. the water in question being placed on a clean white por--I am, &c., celain slab, à corresponding drop of a solution of the LEWIS THOMPSON. protochloride of iron was put close to it, and then the two drops were made to unite by means of a platinum wire, but no visible effect was produced in consequence of the admixture.

The water in this case had been obtained about 1 mile below London Bridge, and a precisely similar negative result was derived from water taken near Vauxhall Bridge, although the amount of concentration was then six times greater than in the first instance; consequently we cannot regard the existence of nitrites in Thames wate as an established fact: and here, perhaps, it may be as well to remark technically that the nitrites in general, but particularly the nitrite of soda, possesses many advantages over the bisulphite of soda for what is called an "antichlore." It is more easily made, it is cheaper, and after being used it may be recovered by evaporation in the form of nitrate, and again converted into nitrite for repeated use. Moreover, it does not by its employment lead to the production of an acidulously destructive compound like bisulphate of soda, because the nitrite of soda, when used as an antichlore, is merely converted into a neutral nitrate, after having arrested the injurious influence of two atoms of chlorine.

Whilst upon the subject of Thames water, it is interesting to review an observation made by Berzelius, which may be found at page 686 of the fifth volume of his "Chemistry," translated into French by Valerius. After quoting numerous experiments made by Woehler, Ehrenberg, and Morren, which prove that the effect of infusorial animals in water is to oxidise the water, and generate an air contatning 51 per cent of oxygen and 49 per cent of

CHEMICAL

NOTICES FROM FOREIGN
SOURCES.

NOTE.-All degrees of temperature are Centigrade, unless otherwise expressed.

Comptes Rendus Hebdomadaires des Seances, de l'Academie des Sciences. No. 4, July 24, 1876. Observation of the Portion of the Spectrum Below the Red Ray by means of the Effects of Phosphorescence.-M. E. Becquerel.-We may follow by direct vision some of the effects produced in this region of the spectrum. We find thus merely some rather large absorpsion-bands, and to distinguish these it is necessary to have a very intense light. It is probable that many lines and narrower bands may escape this means of observation. The margins of the images are not well defined, except those of the region A", A"" (the more and the less refrangible parts of the spectral region below the red). On the other hand, the observations do not extend much beyond A", and do not comprehend all the space where the thermic phenomena are observable. This may depend on the limits within which the effects of phosphorescence are appreciable, and which may not be the same as those of the thermic spectrum. The author's method is to fix a highly phosphorescent substance, such as an alkalineearthy sulphide, upon paper or glass by means of gum, and

CHEMICAL NEWS,}

August 25, 1876.

Chemical Notices from Foreign Sources.

having excited it by the action of diffused light to observe, the extinction of phosphorescence produced by this part of the spectrum. This extinction causes unequally active parts to appear, i.e., spaces corresponding to the black rays or bands of the spectrum.

Paraldol, an Isomeric Modification of Aldol.-M. A. Wurtz.-This compound softens at 80°, and is melted at 90°. It dissolves readily in water and alcohol, from which latter it is obtained in fine anorthic prisms.

Reply of M. Hirn to the Criticism of M. Ledieu in "Comptes Rendus," July 10, 1876.-M. Hirn complains that M. Ledieu ascribes to him the very views which he is attempting to refute.

Production of the Electric Effluve.-M. A. Boillot. -The author, in experimenting upon the chemical action of the effluve, makes use of the following arrongement :Two narrow tubes, filled with graphite in powder and calcined, and are parallel to and near each other. They are inserted with their whole length in a test-tube about 18 centimetres in length, and they terminate each with a platinum wire communicating with the carbon. The wire from one of these tubes traverses the test-tube to its upper part; the other is bent back in a downward direction. Two other tubes enter the test-tube; the one ends at the summit, and the other penetrates to 2 or 3 centimetres of the orifice. The first is destined to introduce the gases, and the second to collect them. The effluve is produced in the space between the two carbon conductors.

Photometric Researches on Coloured Flames.M. Gouy.-Not suitable for abstraction.

Note on the Radiometer.-M. A. Gaiffe.-The author has made a modification, which he considers proves that the actinic and thermic rays act upon this instrument. It is a radiometer of the ordinary form, the discs being coloured a dead blue on one surface and a dead red on the other. It may be made to revolve in either direction by using alternately suitable sources of heat and light. If, e.g., we expose this instrument to the sunlight, the blue surfaces acquire a predominant action, and after some moments hesitation the mill begins to turn from the left to the right. If it is exposed to the flame of a common gas-jet, or of a Bunsen burner, or to the radiations of a plate of hot iron the rotation takes place in an inverse

direction.

83

dered insensible, though it turned very quickly if a vacuum was made without heating in the ordinary manner. But if the discs, instead of being made of two metals, were made half of metal and half of mica the instrument could not be rendered insensible. The glass case was pierced by an electric discharge, when the radiometer began to turn with great speed, and continued for an hour. The aperture was so small that its diameter could be approximately estimated only by the aid of a powerful microscope. It was found practicable to re-form a vacuam in this instrument up to 100 m.m., even though perforated; rotation then took place in the ordinary manner. Nos. 6, 7, and 8, are radiometers with discs of mica and varnished copper, green, blue, red, and yellow; the colours, in these conditions, have no effect on the radiation.

Cause of the Motion of the Radometer.-M. G. Salet. According to all the experiments made, the cause of movement in the various apparatus resembling the radiometer of Crookes is a difference in the temperature of the surfaces of the discs. The theory of Tait appears the best. A disc, compound or simple, whose surfaces have actually two different temperatures, and which is plunged into a highly rarefied atmosphere, begins to move, the hottest surface recoiling. Whilst the difference of temperature exists the movement continues. There is no occasion to bring forward the possible action of gases condensed on the surfaces. Wherever two thermometers, isolated in a vacuum, and constructed of two different substances, A and B, would indicate different temperatures, a radiometer disc composed of adjacent laminæ, the one of the substance A and the other of B, will begin to move, and the movement will show the direction and the degree of the difference of temperature. In the circle of lights the discrepancy between the indications of two thermofor an indefinite time; it is the same with the movement meters, the one with its bulb blackened maintained itself of the radiometer. Not content with repeating the exper-meter in the centre of a sphere of opal glass so as to ment of Mr. Crookes and M. Fizeau, by placing the radioequalise the light and avoid currents of air, the author has made an experiment which he considers absolutely demonstrative. He has fixed upon the mill of a radiometer the needle of a compass: the discs were composed of two laminæ of burnt mica, one of them blackened. Under the influence of an adjacent flame the needle deviated to a certain angle, and variations in the lustre or in the distance of the flame were shown very distinctly by a corresponding change in the deviation. The source of light having remained constant for four days the needle kept its position invariable for the whole of the time. The action of condensed gases cannot be invoked here.

Decomposition of Alkaline Bicarbonates, Moist or Dry, under the Influence of Heat and of a Vacuum. soda is not sensibly decomposed in a vacuum at 20° to 25°. -M. A. Gautier.-Perfectly pure and dry bicarbonate of At 100° it is rapidly decomposed in dry air. Solutions of bicarbonate of soda in water set to evaporate in a vacuum are decomposed at 20° to 25°, and this the more rapidly the greater the quantity of the water. The bicarbonate of potassa is decomposed much less rapidly at elevated temperatures than the corresponding soda salt.

Radiometers composed of Laminæ of Different Materials. MM. Alvergniat Freres.-The following observations have been made with radiometers with discs of different materials. No. I is a radiometer with discs of silver and transparent mica. In the light the radiometer turns with the mica in front and the silver repelled; in obscure heat, with the radiometer plunged in water at 30° or 40°, the rotation is in the opposite direction. In ice it turns as if exposed to light. No. 2 is composed of aluminium and blackened mica. In the light this radiometer turns with the metal first, and the blackened surface repelled. Obscure heat and light, however intense, do not modify the direction of the rotation. If plunged in ice it turns in the opposite direction. No 3 is formed of aluminium and mica not blackened. In light this radiometer turns with the mica first. In ice the rotation is in the same direction as in light. Dark heat niakes it turn in the Geological Age of Certain Metallic Veins, and, in opposite direction, with the metal first. With this radio-particular, of Mercury.-M. Virlet d'Aoust.-The author meter M. Jamin made the following experiment:-He concludes that in the Asturias, as in Mexico and France, directed a small light upon one point of the radiometer mercury is of very modern origin. while in motion, so as to heat only a single point of the globe. This threw the discs into such a state of equilibrium, that instead of rotation there ensued oscillations like those of a pendulum. The two surfaces of the discs, the metal and the mica, are both repelled: if the distance of the flame is varied one of the two laminæ is repelled more or less. No. 5 is a radiometer with discs of silver and aluminium. This radiometer has been heated to 440°, distilling sulphur, and continuing to make a vacuum with the aid of the mercurial pump. The instrument was ren

Les Mondes, Revue Hebdomadaire des Sciences,
No. 14, August 3, 1876.

Occurrence of the Germs of the Tape-worm in Meat.-An article taken from the Abeille Medicale points out the danger of eating meat in the half-raw condition, called by some persons "rare," as the ova of the tapeworm are only killed by thorough cooking. Those whose

Principal-J. G. GREENWOOD, LL.D.
Professors and Lecturers.

Mr. A. Greek-J. G. Greenwood, LL.D., Fell. Univ. Coll., Lond.
Latin; Comparative Philology-A. S. Wilkins, M.A., Fell. Univ. Coll,
Lond.
English Literature; Ancient and Modern History-A. W. Ward,
M.A., Fell. St. Peter's Coll., Camb.

CHEMICAL NEWS,}

Sept 1, 1876.

THE

CHEMICAL NEWS. hyposulphite.

VOL. XXXIV. No. 875.

ON A

NEW PROCESS FOR THE QUALITATIVE
DETECTION AND THE DETERMINATION
OF POTASSA.

By M. A. CARNOT.

In spite of the improvements in the estimation of potassa introduced by Peligot and Schloesing, its exact determination in a somewhat complex substance remains one of the most delicate operations in analytical chemistry. We have, further, no reagent sensitive enough to detect its presence in small quantities.

The new reaction of the salts of potassa in presence of hyposulphite of soda and a salt of bismuth in a solution mixed with alcohol solves both these difficulties.

The solution of the potassic salt is placed in a small flask, the bismuth solution is added, then the hyposulphite, the whole is mixed rapidly, and 200 to 250 c.c. of concentrated alcohol are added. The whole is agitated for a few moments, and left to settle. The yellow precipitate collects at the bottom of the flask, and may be filtered after a quarter of an hour, and carefully washed with alcohol. The precipitate cannot be weighed; it is dissolved upon the filter in excess of water; the bismuth is thrown down as sulphide by sulphydrate of ammonia, washed by decantation, collected on a tared filter, dried at 100°, and weighed. The weight obtained may be corrected by separating from the filter a part of the dried precipitate, and heating it again to 150° to 200° in a small platinum crucible, weighing before and after, and correcting the total weight of the sulphide accordingly. The weight of the potassa is found on multiplying the weight of the sulphide of bismuth found by

The method has been found accurate in presence of soda, lithia, ammonia, lime, magnesia, alumina, and iron.

We dissolve in a few drops of hydrochloric acid 1 part-Comptes Rendus. of the subnitrate of bismuth-say half a grm.—and, on the other hand, about 2 parts (1 grm. to 1) of crystallised hyposulphite of soda in a few c.c. of water. The second solution is then poured into the first, and concentrated alcohol is added in large excess. This mixture is the reagent.

If brought in contact with a few drops of the solution of a potash-salt it at once gives a yellow precipitate. With an undissolved potassic salt it produces a decidedly yellow colouration, easily recognised.

All potassic salts with mineral acids are equally susceptible of this reaction, sulphates and phosphates as well as nitrates, carbonates, chlorides, &c. It is also very sensitive with the organic salts, tartrates, citrates, &c. The reaction is not interfered with by the presence of other bases with which nothing analogous is produced. The character is, therefore, perfectly distinct.

Baryta and strontia alone may occasion some difficulty, by reason of the white precipitates of double hyposulphites which they form with the same reagent; but it is very rare to meet them along with potassa, and they are very easily detected and removed.

If we have a solution containing merely a few milligrms. ot potassa, it is reduced by evaporation to a very small volume, or even to dryness, when the characteristic reaction readily appears. Or slips of filter-paper may be repeatedly saturated with the dilute solution, and after drying be steeped in the alcoholic reagent, when the yellow colour will appear, especially on the margins of the paper. The author's quantitative experiments refer chiefly to nitrates, chiorides, and mixtures of the two salts. With some special precautions the method may probably be applied directly to sulphates, though these are easily converted into chlorides by chloride of barium, removing the excess of baryta with sodic or ammonic carbonate.

The hyposulphite of commerce is sufficiently pure for use; the crystals are dissolved in a small quantity of water at the moment of the experiment.

The chloride of bismuth is prepared by treating the pulverised metal with a few drops of nitric acid, evaporating to dryness, and then heating with a very small quantity of hydrochloric acid. The lead possibly present in the bismuth is got rid of by adding to the cold solution concentrated alcohol, which causes chloride of lead to be deposited. Or subnitrate of bismuth may be dissolved in a few drops of hydrochloric acid.

The liquid in which the potassa is to be determined should not exceed 10 to 15 c.c. in bulk, so that the entire volume of the aqueous solutions may not exceed 20 to 25

C.C.

For I part of supposed potassa we take 2 parts of

NOTICE ON THE OIL OF WOOD.

By M. GUIBOURT.

Mr.

THIS curious product of India, called by the English
wood-oil or Gurjun balsam, forms already the subject of
two papers published in the Pharmaceutical Journal,
by Messrs. Charles Lowe and Daniel Hanbury.
C. Lowe, who only knew that this resinous liquid is
extracted in India, by incisions made in the tree, considers
it as a Copaiva balsam rendered turbid by a greenish
resin held in suspension. The filtered balsam forms a
brown and transparent liquid, from which we withdraw by

distillation

Volatile oil..
Hard resin..

65 34 I

Water and acetic acid According to Mr. Lowe the volatile oil possesses all the characters of that of copaiva, and the hard resin, which he regards as pure copaivic acid, free from the soft resin, which, according to him, exists in the most part of commercial copaivas, seemed to him to indicate a superior quality as a medicine. I avow that I scarcely understand this conclusion, and that I am so much the less convinced of the identity of the hard resin with copaivic acid as Mr. Lowe has observed in the new resinous balsam the singular property of solidifying when exposed, in a closed vessel, to a temperature of 230° F.; copaiva presents nothing similar. I find further this difference, that the new balsam distilled with an addition of a little quantity of an oxidising body as chlorine, hypochlorite of lime, or bichromate of potash, furnishes an essence of a beautiful blue colour, whilst common copaiva with soft resin scarcely furnishes any coloured essence. The notice concludes with a mention of a falsification which appeared to me at once ill-founded and little to be feared; it is that cold sulphuric acid produces with copaiva a purple colouration like that obtained with cod-liver oil, to such an extent that dishonest persons might sell a mixture of olive oil or any other fatty oil with a little quantity of copaiva for cod-liver oil. Mr. D. Hanbury tells us in his notice that oil of wood is extracted from Dipterocarpus turbinatus by quite a peculiar process, which I shall describe in a few words, in order to make the nature of the product better known. To obtain it a large incision is made in the trunk of the tree, about 30 inches from the ground, upon

86

Development of the Chemical Arts.

{CHEMICAL NEWS,.

Sept. 1876.

manifest when, after agitation, a thin layer of the liquid covers the upper side of the bottle. Then in whatever manner we look at this layer there appears a beautiful green colour. The same green colour appears again and becomes permanent when, after having dissolved the woodoil in alcohol, we leave the liquid to spontaneous evaporation; we then see towards the top of the capsule, between the parts of green resin, white radiating tufts belonging to a particular principle of which I leave the examination to those who have a larger quantity of the material at their disposal. As for the resin it has acquired a permanent green colour, which we find in a dry resin which remains when we boil wood-oil and water for a very long time. This green colour which is also that of the beautiful resin of Piney (Vateria indica) which was seen in the Exhibition, establishes a point of comparison between two products which come from trees belonging to the same family, the Dipterocarpeæ; but the resemblance stops there, for the resin of the Vateria indica is insoluble in alcohol and very imperfectly soluble in ether, whilst the green resin of the wood-oil is easily soluble in these two mediums. Finally, the wood-oil derived from the Exhibition behaves like copaiva with ammonia and calcined magnesia. It is solidified very promptly with 1-16th of calcined magnesia, and its mixture with ammonia becomes again liquid and tolerably transparent after a momentary opacity. I am far from concluding with Mr. Lowe that the two oleoresinous bodies are chemically identical; but with regard to their medical uses I think that all the turpentines and balsams, liquids or even solids, can be useful as remedies for the catarrhal state of the mucous membranes. I conclude by saying that the wood-oil of Mr. Hanbury and that derived from the Exhibition have not probably been extracted by the same method. The first has been obtained by the aid of fire, by the process described by Roxburgh; ths second has, without doubt, been obtained without the intervention of this agent, for I do not find the characteristic features of oils which result from the action of fire on resin.-Journal de Pharmacie et de Chimie.

which they kindle and maintain a fire so that the incision | colour of the red does not then appear, but it becomes may be charred; soon after the liquid begins to run. It is conducted by means of a little gutter, into a vessel destined to receive it. The average yield of the best trees during a season is from 30 gallons, &c. Roxburgh adds that oil of wood is also produced by the Dipterocarpus incarnus, alatus, and costatus. The first is reputed to furnish the best sort and in the largest quantity. Oil of wood, which makes the object of Mr. Hanbury's notice, has been imported in a large quantity from Moulmein, in British Burmah. When filtered it forms a transparent liquid of a very deep brown by transmitted light, but it scems opaque and of an obscure green when seen by reflection. It possesses then in a very marked degree the dichroism obverved in all resinous oils obtained by fire. I insist on this character, which settles the nature of the wood-oil, which is not simply a natural product like copaiva, but which results, in part at least, from a liquid modification of the resin of Dipterocarpus obtained by the action of fire. This oil of wood from Moulmein is more consistent than olive oil; it weighs o'964, and possesses an odour and a taste very analogous to copaiva. It dissolves in twice its own weight of absolute alcohol, with the exception of a little quantity of matter which is separated on standing. But the most curious property of this oil, already noticed by Mr. Lowe and observed anew by Mr. Hanbury, is that it solidifies when heated in a stoppered vial at 266° F.; at this temperature the oil becomes turbid and so gelatinous that it is not displaced by the inversion of the vessel. After cooling the solidification becomes more complete; but a gentle heat aided by a slight agitation re-establishes its former fluidity. Mr. Lowe had indicated the temperature of 230° F. for the solidification of wood-oil. I suppose that the difference of temperature pointed out by the two observers depends on that of the liquids upon which they have operated; for just as the copaiva furnished by various copahifera of America, or the turpentines produced by the different species of pines and firs, are not identical, it is very reasonable to think that the oils of wood furnished by Dipterocarpus turbinatus, incarnus, alatus, costatus, &c., are not absolutely alike; the higher or lower temperature which the oil has undergone may be also a cause of variation in the properties of the product. What I say here is not a supposition; it is a fact at present certain. In the Universal Exhibition of 1855, there were two samples of wood-oil, one coming from Canara the other from Tenasserim. One of these samples, I do not know which, contained in a little pot of white earthenware which, of an intermediate grade between stoneware and porcelain, had been given by Dr. Royle to M. Delasse, a member of the International Jury, charged to give a report on the bitumens and petroleums admitted to the Exhibition. M. Delasse, not finding there what he sought, sent back the sample, which I judged in consequence ought to be the new copaiva announced by Mr. Lowe. It approximates, in fact, much more to the balsam examined by Mr. Lowe than to that for which I am obliged to Mr. Hanbury. The wood-oil of Mr. Hanbury has nearly the liquidity of olive oils; if placed between the eye and the sun it is completely transparent and of the colour of dark Malaga wine; by reflection it seems opaque and of an olive green. It behaves with ammonia and magnesia in a very different manner from copaiva. Mixed with liquid ammonia at 22° B., in the proportion by weight of 5 parts of balsam to 2 of alkali, it forms immediately an opaque and very thick mixture which does not change by time. It is not solidified by 1-16th of calcined magnesia; the two stances separate on standing. The wood-oil of M. Delasse has the aspect of a thick and slightly gelatinous liquid. After having deposited a little green resin, which is held in suspension, it becomes almost transparent; if placed between the eye and the sun it is of a very deep red; if seen by reflection it appears still red but turbid, and resembles a liquid in which fine powder of cochineal has been suspended by agitation. The complementary

REPORT

ON THE

DEVELOPMENT OF THE CHEMICAL ARTS
DURING THE LAST TEN YEARS.*
By Dr. A. W. HOFMANN.
(Continued from p. 78.)

Chlorine, Bromine, Iodine, and Fluorine.
By Dr. E. MYLIUS, of Ludwigshafen.

FOR the latter purpose Kunheim utilises the chlorine obtained on Deacon's method. The chlorine is here so completely absorbed by the milk of lime through which it passes that mere traces are contained in the air escaping from the exhauster. The draft in the entire apparatus is kept up by any aspiratory arrangement beyond the chloride of lime chambers and measured by an anemometer constructed by Hurter. The latter consists of a U-tube of 5-16ths c.m. internal diameter, with legs about 25 c.m. in length. As one leg of this tube is always in communication with the gaseous current, the pressure occasioned by the current is always shown in the other leg by the tube by the displacement of a liquid therein sub-contained (ether). The U-tube is fixed so that the leg containing the liquid lies flat on a graduated inclined plane, which may be raised or lowered on a frame fitted with a level. The meniscus of the liquid is thus extended diagonally, and the small vertical divisions of the scale are magnified into long horizontal degrees. Kunheim uses a simple upright U-tube filled with ether.

"Berichte über die Entwickelung der Chemischen Industrie Während des Letzten Jahrzehends."