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THE CHEMICAL

VOL. XXXIX. No. 1007.

This ammonia water contains about 1'5 per cent. of NEWS. ammonia; hence the total quantity of the volatile alkali obtainable from the gasworks in England amounts to some 9000 tons per annum.

A NEW CHEMICAL INDUSTRY, ESTABLISHED BY M. CAMILLE VINCENT.* By Prof. ROSCOE, LL.D., F.R.S.

"AFTER I had made the discovery of the marine acid air, which the vapour of spirit of salt may properly enough be called, it occurred to me that, by a process similar to that by which this acid air is expelled from the spirit of salt, an alkaline air might be expelled from substances containing the volatile alkali. Accordingly I procured some volatile spirit of sal-ammoniac, and having put it into a thin phial and heated it with a flame of a candle, I presently found that a great quantity of vapour was discharged from it, and being received into a basin of quicksilver it continued in the form of a transparent and permanent air, not at all condensed by cold." These words, written by Joseph Priestley rather more than one hundred years ago, describe the experiment by which ammonia was first obtained in the gaseous state.

Unacquainted with the composition of this alkaline air, Priestley showed that it increased in volume when electric sparks are passed through it, or when the alkaline air (ammonia) is heated the residue consists of inflammable air (hydrogen).

Berthollet, in 1785, proved that this increase in bulk is due to the decomposition of ammonia into nitrogen and hydrogen, whilst Henry and Davy ascertained that two volumes of ammonia are resolved into one volume of nitrogen and three volumes of hydrogen.

The early history of sal-ammoniac and of ammonia is very obscure. The salt appears to have been brought into Europe from Asia in the seventh century, probably from volcanic sources. An artificial mode of producing the ammoniacal salts from decomposing animal matter was soon discovered, and the early alchemists were well acquainted with the carbonate under the name of Spiritus salis urinæ. In later times sal-ammoniac was obtained from Egypt, where it was prepared by collecting the sublimate obtained by burning camels' dung.

Although we are constantly surrounded by an atmosphere of nitrogen, chemists have not yet succeeded in inducing this inert substance to combine readily, so that we are still dependent for our supply of combined nitrogen, whether as nitric acid or ammonia, upon the decomposition of the nitrogenous constituents of the bodies of plants and animals. This may be effected either by natural decay, giving rise to the ammonia which is always contained in the atmosphere, or by the dry distillation of the same bodies, that is, by heating them strongly out of contact with air; and it is from this source that the world derives the whole of its commercial ammonia and salammoniac.

Coal, the remains of an ancient vegetable world, contains about 2 per cent. of nitrogen, the greater part of which is obtained in the form of ammonia when the coal undergoes the process of dry distillation. In round numbers two million tons of coal are annually distilled for the manufacture of coal gas in this country, and the ammoniacal water of the gasworks contains the salt of ammonium in solution.

According to the most reliable data 100 tons of coal were distilled so as to yield 10,000 cubic feet of gas of specific gravity o'6, giving the following products, in tons:

*

Gas. 22.25

Tar. Ammonia Water. Coke.

8.5

9'5

59'75 average.

A singular difference is observed between the dry distillation of altered woody fibre as we have it in coal, and woody fibre itself. In the products of the first operation we chiefly find in the tar the aromatic hydrocarbons, such as benzene, whilst in the second we find acetic acid and methyl alcohol are predominant.

The year 1848 is a memorable one in the annals of revolutionary chemistry, for in that year Wurtz proved that ammonia is in reality only one member of a very large family. By acting with caustic potash on the nitrates of the alcohol radicals he obtained the first series of the large class of compound ammonias the primary monamines, Of these niethylamine is the first on our list :

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To these bodies the names of methylamin, di-methylamin, and tri-methylamin were given. They resemble ammonia in being volatile alkaline liquids or gases, which combine with acids to form crystalline and well-defined salts.

Hitherto these compound ammonias have been chemical curiosities; they have, however, recently become, as has so often been the case in other instances, of great commercial importance, and are now manufactured on a large scale.

We are all well aware that the French beet-root sugar industry is one of great magnitude, and that it has been largely extended in late years. In this industry, as in the manufacture of cane sugar, large quantities of molasses or treacle remain behind after the whole of the crystallisable sugar has been withdrawn. These molasses are invariably employed to yield alcohol by fermentation. The juice of the beet, as well as that of cane-sugar, contains, in addition to the sugar, a large quantity of extractive and nitrogenous matters, together with considerable quantities of alkaline salts. In some sugar-producing districts the waste-liquors or spent-wash from the stills-called vinasses in French-are wastefully and ignorantly thrown away, instead of being returned to the land as a fertiliser, and thus the soil becomes impoverished. In France it has long been the custom of the distiller to evaporate these liquors (vinasses) to dryness, and to calcine the mass in a reverberatory furnace, thus destroying the whole of the organic matter, but recovering the alkaline salts of the beet-root. In this way 2000 tons of carbonate of potash are annually produced in the French distilleries. For more than thirty years the idea has been entertained of collecting the ammonia-water, tar, and oils which are given off when this organic matter is calcined, but the practical realisation of the project has only quite recently been accomplished, and a most unexpected new field of

A Discourse given at the Royal Institution of Great Britain, chemical industry thus opened out, through the persevering

Friday, February 21, 1879.

and sagacious labours of M. Camille Vincent, of Paris.

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The following is an outline of the process as carried out at the large distillery of Messrs. Tilloy, Delaune, and Co., at Courrières. The spent-wash having been evaporated until it has attained a specific gravity of 131, is allowed to run into cast-iron retorts, in which it is submitted to dry distillation. This process lasts four hours; the volatile products pass over, whilst a residue of porous charcoal and alkaline salts remains behind in the retort. The gaseous products given off during the distillation are passed through coolers, in order to condense all the portions which are liquid or solid at the ordinary temperature, and the combustible gases pass on uncondensed and serve as fuel for heating the retorts.

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{CHEMICAL NEWS,

March 14, 1879.

distillation of wood) by containing in addition methyl alcohol, methyl sulphide, methyl cyanide, many of the members of the fatty acid series, and, most remarkable of all, large quantities of the salts of trimethylamin.

The tar, on re-distillation, yields more ammonia water, a large number of oils, the alkaloids of the pyriden series, solid hydrocarbons, carbolic acid, and, lastly, a pitch of fine quality.

The crude alkaline aqueous distillate is first neutralised by sulphuric acid, and the saline solution evaporated, when crystals of sulphate of ammonia are deposited; and these, after separating and draining off, leave a mother. liquor, which contains the more soluble sulphate of trimethylamin. During the process of concentration, vapours of methyl alcohol, méthyl cyanide, and other nitriles are given off, these being condensed, and the cyanide used for the preparation of ammonia and acetic acid by decomposing it with an alkali.

Trimethylamin itself is at present of no commercial value, though perhaps the time is not far distant when an important use for this substance will be found. The question arises as to how this material can be made to yield substances capable of ready employment in the arts. This problem has been solved by M. Vincent in a most ingenious way. He finds that the hydrochlorate of trimethylamin, when heated to a temperature of 260°, decomposes into (1) ammonia, (2) free trimethylamin, and (3) chloride of methyl.

3NMe3HCl=2N Me3+NH3+3 MeCl.

By bubbling the vapours through hydrochloric acid the alkaline gases are retained, and the gaseous chloride of methyl passes on to be purified by washing with dilute caustic soda and drying with strong sulphuric acid. This is then collected in a gas-holder, whence it is pumped into strong receivers and condensed.

The construction of these receivers is shown in Fig. 1. They consist of strong wrought-iron cylinders, tested to resist a pressure of 20 kilos. per square centimetre, and containing 50, 110, 220 kilos. chloride of methyl. The liquid is drawn from these receivers by opening the screw tap D, which is covered by a cap c, to prevent injury during transit.

Both ammonia and chloride of methyl are, however, substances possessing a considerable commercial value. The latter compound has up to this time, indeed, not been obtained in large quantities, but it can be employed for two distinct purposes: (1) it serves as a means of producing artificial cold; (2) it is most valuable for preparing methylated dyes, which are at present costly, inasmuch as they have hitherto been obtained by the use of methyl iodide, an expensive substance.

Methyl chloride was discovered in 1804 by MM. Dumas and Péligot, who obtained it by heating a mixture of common salt, methyl alcohol, and sulphuric acid. It is a gas at the ordinary temperature, possesses an ethereal smell and a sweet taste, and its specific gravity is 1738. It is somewhat soluble in water (about 3 vols.), but much more in acetic acid (40 vols.), and in alcohol (35 vols.). It burns with a luminous flame, tinged at the edges with green, yielding carbonic and hydrochloric acids. Under pressure methyl chloride can be readily condensed to a colourless, very mobile liquid, boiling at -23° C. under a pressure of 760 m.m. As the tension of the vapour is not high, and as it does not increase very rapidly with the temperature, the liquefaction can be readily effected, and the collection and transport of the liquefied chloride can be carried on without danger.

The following table shows the tension of chloride of methyl at varying temperatures:

At o° the tension of CH3Cl is 2:48 atmospheres.

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4'11 4.81 5:62

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39° 35°

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From these numbers we must of course subtract 1 to obtain the pressure which the vapour exerts on the containing vessel.

As a means of producing low temperatures chloride of methyl will prove of great service both in the laboratory and on a larger industrial scale. When the liquid is allowed to escape from the receiver into an open vessel, it begins to boil, and in a few moments the temperature of the liquid is lowered by the ebullition below -23°, the boiling-point of the chloride. The liquid then remains for a length of time in a quiescent state, and may be used as a freezing agent. By increasing the rapidity of the evaporation by means of a current of air blown through the liquid, or better by placing the liquid in connection with a good air-pump, the temperature of the liquid can in a few moments be reduced to -55°, and large masses of mercury easily solidified. The construction of a small freezing machine employed by M. Camille Vincent is shown in Fig. 2. It consists of a double-cased copper vessel, between the two casings of which the FIG. 2.

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methyl chloride (A) is introduced. The central space (M) is filled with some liquid such as alcohol, incapable of solidification. The chloride of methyl is allowed to enter from the cylindrical reservoir by the screw tap (B) and the screw (s) left open to permit of the escape of the gas. As soon as the whole mass of liquid has been reduced to a temperature of -23°, ebullition ceases, the screw (s) may be replaced, and if a temperature lower than -23° be required the tube (B) placed in connection with a good air-pump. By this simple means a litre of alcohol can be kept for several hours at temperatures either of -23° or 55°, and thus a large number of experiments can be performed, for which hitherto the expensive liquid nitrous oxide or solid carbonic acid was required.

M. Vincent has recently constructed a much larger and more perfect and continuous form of freezing machine, in which by means of an air-pump and a forcing-pump the chloride of methyl is evaporated in the freezing machine and again condensed in the cylinders. This enlarged form of apparátus will probably compete favourably with the ether, and sulphurous acid, freezing machines now in

use, as they can be simply constructed, and as the vapour and liquid do not attack metal and are non-poisonous, and as the frigorific effects which it is capable of producing are most energetic.

The second and perhaps more important application of methyl chloride is to the manufacture of methylated colours.

It is well known that rosanilin or aniline-red, Cao H19N3, yields compounds possessing a fine blue, violet, or green colour, when a portion of the hydrogen has been replaced by the radicals methyl or ethyl, and the larger the proportion of hydrogen replaced the deeper is the shade of violet which is produced. Thus we have triethyl rosanilin or Hofmann's violet, C20H16(C2H5)3N3.

By replacing one or two atoms of the hydrogen of aniline by methyl and by oxidising the methyl anilines thus obtained, Charles Lauth obtained fine violet colours, whilst about the same time Hofmann observed the production of a bright green colouring matter, now known as iodine green, formed during the manufacture of the violet, and produced from the latter colour by the action of methyl iodide.

In order to prepare aniline-green from the pure chloride of methyl, a solution of methyl aniline-violet in methyl alcohol is placed in an iron digester and the liquid rendered alkaline by caustic soda. Having closed the digester, a given quantity of liquid chloride of methyl is introduced by opening a tap, and the digester thus charged is placed in a water-bath and heated by a jet of steam, until the temperature reaches 95°, and the indicated pressure amounts to from 4 to 5 atmospheres. As soon as the reaction is complete the hot water is replaced by cold, and the internal pressure reduced by opening the screw tap of the digester. The product of this reaction heated and filtered, yields the soluble and colourless base, whose salts are green. To the acidulated solution a zinc salt is added to form a double salt, and the green compound is then precipitated by the addition of common salt. By adding ammonia to a solution of the green salt, a colourless liquid is obtained, in which cloth mordanted with tannic acid and tartar emetic becomes dyed of a splendid green.

If rosanilin be substituted for methyl aniline in the preceding reaction Hofmann's violet is obtained. The application of methyl chloride to the preparation of violets and greens is, however, it must be remembered, not due to M. Vincent; it has been practised for some years by aniline-colour makers. M. Vincent's merit is in establishing a cheap method by which perfectly pure chloride of methyl can be obtained, and thus rendering the processes of the manufacture of colours much more certain than they have been hitherto.

The production of methyl violet from dimethyl aniline may be easily shown by heating this body with a small quantity of chloral hydrate, and then introducing some copper turnings into the hot liquid. On pouring the mixture into alcohol, the violet colour is well seen.

In reviewing this new chemical industry of the beetroot vinasses, one cannot help being struck by the knowledge and ability which have been so successfully expended by M. Camille Vincent on the working out of the processes.

Here, again, we have another instance of the utilisation of waste chemical products and of the preparation on a large scale of compounds hitherto known only as chemical

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rarities.

All those interested in scientific research must congratulate M. Camille Vincent on this most successful issue of his labours.

The Spottiswoode Testimonial.-The Committee. appointed to receive subscriptions to present a bust of Mr. William Spottiswoode, Pres. R.S., to the Royal Institution as a testimonial of his valuable services as its Treasurer and Secretary successively, have engaged Mr. Richard Belt as the sculptor.

Hofmann, Proc. Rov. Soc, xiii., 13, 1863. t

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VICTOR AND CARL MEYER'S NEW METHOD OF DETERMINING VAPOUR-DENSITIES.

By GREVILLE WILLIAMS, F.R.S.

A GREAT number of processes for determining vapourdensities have been published during the last few years, but by far the greater number of them have only been used by their inventors, and none of them have entirely superseded the processes of Gay-Lussac and Dumas for determinations at ordinary pressures.

The last process of Victor and Carl Meyer* has, however, had a different fate, and from the moment it was published excited the earnest attention of chemists and physicists. In simplicity and accuracy it leaves nothing to be desired, and it possesses the great merit of being available at all temperatures up to the softening point of glass; and, doubtless, if the apparatus were constructed in metal its range of usefulness would be still further increased. In fact, MM. Victor and Carl Meyer may be congratulated upon having devised a method of determining vapour-densities which will probably supersede all those in use at the present time for ordinary pressures. Amongst its other merits it can be constructed by any one with the greatest ease with the materials which are to be found in every laboratory.

Having to determine the vapour-densities of two fractions of B-lutidine, supposed to be very nearly pure, I improvised an apparatus for the purpose. In all essential features it resembled that of Victor and Carl Meyer. The glass flask c, in the illustration, p. 66, was, however, replaced by an iron tube closed at the lower end, which happened to be in the laboratory. It was charged with aniline. The long neck of the vapour flask, b, was cut off two inches below the lateral tube, a, and, the two ends being brought close together, were joined by an india-rubber tube; the object being to give the apparatus some flexibility, and lessen the chances

CHEMICAL NEWS, March 14, 1879.

ON THE ACTION OF NUCLEI, &c.

By C. TOMLINSON, F.R.S.

My paper to which Mr. Grenfell refers (CHEMICAL NEWS, vol. xxxix., p. 16) was not read in September, 1877, and its object was not "to upset his theories and establish my own." Is it not possible for a scientific man to be anxious only for the truth? That I was so will appear from the fact that Mr. Grenfell showed me some of his experiments, and although I did not agree with his conclusions, while he decidedly opposed mine, I asked him to draw up an account of them for the Royal Society, and I promised to present his paper, which I accordingly did, and it was read and printed in the Proceedings.

My object in repeating Mr. Grenfell's experiments was to see whether any fresh hint could be gathered from them. I never once mentioned my own theory; but I gained this useful piece of information, viz., "that supersaturated saline solutions behave differently among themselves and to different bodies under varying atmospheric conditions ;" and that "an oil, &c., introduced into the closed flask, as in M. Viollette's and Mr. Liversidge's experiments, may be inactive, while under the other conditions the same oil may be active." I give abundant proof that this is so in a subsequent paper, which Mr. Grenfell does not appear to have seen; while in a third paper the powerful influence of the sides of the vessel in maintaining the state of supersaturation is dwelt upon.

As space is valuable in the CHEMICAL NEWS I will not which throws no light upon the question as to what are follow Mr. Grenfell in his method of minute criticism, the precise conditions under which these solutions become the whole work. That is a fair subject for discussion; solid. Mr. Grenfell says that it is absorption that does but I must protest against the general tone of Mr. Grenfell's note, especially that part of it which makes me so silly as not to know the simple conditions under which he conducted his experiments. In such a censure he, unLöwel, Viollette, and Liversidge, who expressly say that consciously perhaps, includes such good observers as hydrated, are incapable of determining the solidification of these solutions. I stated in one of my early papers that I do not agree to this, and in a paper which is now being prepared the reasons will be given more distinctly.

of fracture of the tube a, which had been drawn out somewhat too finely. These details are merely mentioned to show that, as long as the essential points of the apparatus are pre-porous bodies, bodies greedy of water and capable of being served, some latitude may be permitted in putting it together. In my first apparatus the funnel d was made as directed, but subsequent experience has shown that it is unnecessary, as the small tube is easily closed by an india-rubber stopper without the necessity for enlarging the aperture.

A preliminary experiment was made with water with the following result:

S=

t =

0.0207 grm. 13.1°

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In conclusion, I never said or implied that Mr. Grenfell denied the result of the well-known lecture table experiment with Glauber's salts. I may also add that the early observers saw the objections to cotton-wool for closing the flasks, and that I am not so careless as to allow crystals of the salt to exist in the necks of my flasks before making an experiment.

Highgate, N., March 8, 1879.

Theory. 0.622

Error. +0'021

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LARGE CRYSTAL GROWING.

By CHARLES W. QUIN.

WHEN I was a student I was much given to large crystal growing. My great difficulty was to guard against sudden rises in temperature, which generally had the effect of causing the growing crystal to be partially and unevenly re-dissolved. To receive a continually even temperature, after many experiments I hit upon the plan of plunging the beaker containing the growing crystal into the housecistern, the temperature of the water in which, as I found by trial, never differed by more than o'5° F. either way day or night. To prevent the solution from becoming of half an inch or so a crystal drainer containing a filterexhausted too rapidly I used to immerse in it to the depth paper full of the salt to be crystallised, so that a constant stream of strong solution was continually descending on the growing crystal.

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The PRESIDENT then called on Mr. G. ATTWOOD to read a paper "On the Quantitative Blowpipe Assay of Mercury." The author divides compounds to be assayed into three classes. Class A, containing metallic mercury; cinnabar, tiemannite, suboxide, protoxide, and mixed sulphides. Class B, calomel, corrosive sublimate, and iodide of mercury. Class C, amalgams of gold, silver, copper, lead, zinc, tin, &c. Class A.-10 to 20 grains of the ore, finely powdered and passed through a sieve, 2000 holes to the linear inch, are mixed with 5 to 10 times their weight of powdered litharge and distilled over a spirit-lamp in a small glass retort, 1 inches long and inch in diameter. To this retort is fitted by means of a cork a glass tube, slightly curved, 2 inches long, and ths of an inch in diameter. The end of this tube dips under water contained in a small porcelain crucible. The operation lasts only a few minutes. The mercury is carefully collected from the glass tube and crucible. The retort is broken up and its contents carefully powdered and examined by a lens for mercury. The globules are then united by gently warming under water, and the dry mercury weighed. Class B.-A quantity of the finely powdered ore, equal to 10 grs., is mixed with three times its volume of oxalate of potash and one volume of cyanide of potassium. The apparatus closely resembles that used in class A, but the retort has a small bulb. Class C.These amalgams are sometimes powdered with difficulty, and it is often advantageous to add a known weight of pure mercury, so as to render them semifluid before distilling. 10 to 30 grs. of the amalgam are usually taken for an assay. A turned steel retort is used for distillation, which is effected in a small charcoal furnace heated by a blowpipe flame; the head of the retort is accurately ground to fit over the body. The retort including the cup and cap is I inch high; the neck of the cap is 2 inches long. The paper contains full-size illustrations of the different retorts, &c., which are made by Casella. The author has had much experience, and states that most accurate results can be obtained with the above apparatus.

The next paper was read by Mr. J. W. THOMAS. "On some Points in the Analysis of Combustible Gases and in the Construction of Apparatus." In 1874 the author noticed that when a small quantity of marsh gas was mixed with about three times its volume of oxygen and rarefied until the pressure was 160 m.m. no explosion took place; similarly when mixed with twice its volume of oxygen under a pressure of 130 m.m. the spark did not ignite the mixture. It soon became evident that the cooling effect of the walls of the eudiometer was the chief agent in modifying the force of the explosion. It was also noticed that the expansion of a gas to twice its volume lessened the force of the explosion to a greater extent than the addition of an equal volume of inert gas at the initial pressure. The author accordingly made estimations with marsh gas and hydrogen, using nearly the theoretical quantities of oxygen and a pressure of 160 to 170 m.m., and found that perfectly accurate results were obtained, whilst the safety of the eudiometer tube was not in the least endangered. The author then proceeds to point out the errors which creep in when the long (800 to 900 m.m.) eudiometer tube of Frankland and Ward's or

McLeod's apparatus is used, and proves that the sensitiveness of the apparatus depends on the length of the pressure tube above the top of the eudiometer tube. With the old method of introducing a large excess of oxygen in order to moderate the violence of the explosion, this long eudiometer tube was necessary to contain the large quantity of gas introduced. On the other hand, to lengthen the pressure tube would render it unwieldy from its great length, so that with the old method of introducing a large excess of oxygen the relative lengths of the pressure and eudiometer tubes must remain unaltered; but by employing the reduced tension method proposed by the author, and in which only the theoretical quantity of oxygen required has to be introduced, the necessity for such a long eudiometer tube is obviated. shortened the eudiometer tube to about 500 m.m., retainThe author, therefore, has ing the original length of the pressure tube, and finds that the apparatus has gained in delicacy and is still sufficiently large for all substances. The next modifica tion introduced by the author is the substitution of a steel block with a three way steel tap for the glass taps connecting the barometer tube, eudiometer tube, and pressure bottle. The tubes are fixed and held tight in the steel block by india-rubber rings, screwed down by means of steel collars. Flexibility and absolute tightness are thus secured. As regards the steel tap the author has had no difficulty in keeping it perfectly tight; the three ways are gouged out on the surface of the tap and are not bored. The use of the steel plates connecting the eudiometer and laboratory tubes has been abandoned, and a hollow glass tap substituted, which is so bored that the tubes able by an ingenious mechanical arrangement. The mercury trough is made movesupply of water to keep the apparatus at a constant temperature is brought in at the top of the barometer tube; the exit is at the bottom, and a syphon arrangement is added to ensure a thorough mixing of the water round the top of the eudiometer tube. The little windlass has been modified so that it can be worked with one hand. In conclusion the author gives details as to the management of a gas analysis with the modified method and apparatus; a drawing of the latter accompanies the paper.

can be washed out.

The

Prof. FRANKLAND complimented the author on the ingenuity displayed and the success achieved in his paper.

At the first mention of the return to a use of the steel

stopcock he must confess that he had almost shuddered. Twenty-five years ago when glass stopcocks were a luxury these steel taps constituted a never-ending source of annoyance. After a week's work a leak almost always occurred, which necessitated a prolonged and careful grinding. This might be due to the fact that the tap was made of cast-iron and the plug was bored. The method of exploding gases with almost theoretical quantities of oxygen was a decided step in advance. The shortening of the eudiometer tube and the increased sensitiveness thereby attained seemed to him also most important improvements. He would like to ask Mr. Thomas how the bursting of the flexible tube connected with the pressure bottle was obviated. All plans that he had tried had ultimately failed (winding tape, tubing with canvas in it, &c.).

Dr. WRIGHT suggested that the tubing should be coiled round with bell-wire.

Prof. MCLEOD said that a plan which answered very well was to bind the tube with tape, and cover that with sheet india-rubber to prevent contact of the tape with potash, &c. He had been much struck with the success with which Mr. Thomas had used the theoretical quantity of oxygen without fracturing the eudiometer. In the old apparatus the difficulty was not so much to keep the steel tap tight as to make a tight cement joint between the block and the glass tubes.

Mr. HART suggested that the india-rubber tubing should be wound with tape soaked in glue containing bichromate of potash. On subsequent exposure to light a compound was formed unattacked by acids and alkalies.

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