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THE CHEMICAL NEWS.
| This ammonia water contains about 1'5 per cent. of ammonia ; hence the total quantity of the volatile alkali
obtainable from the gasworks in England amounts to some Vol. XXXIX. No. 1007.
gooo tons per annum.
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 operaA NEW CHEMICAL INDUSTRY,
tion we chiefly find in the tar the aromatic hydrocarbons, ESTABLISHED BY M. CAMILLE VINCENT.* such as benzene, whilst in the second we find acetic acid By Prof. ROSCOE, LL.D., F.R.S.
and methyl alcohol are predominant.
The year 1848 is a memorable one in the annals of re
volutionary chemistry, for in that year Wurtz proved that “ After I had made the discovery of the marine acid air, ammonia is in reality only one member of a very large which the vapour of spirit of salt may properly enough be family. By acting with caustic potash on the nitrates of called, it occurred to me that, by a process similar to the alcohol radicals he obtained the first series of the that by which this acid air is expelled from the spirit of large class of compound ammonias the primary monamines, salt, an alkaline air might be expelled from substances of these piethylamine is the first on our list :containing the volatile alkali. Accordingly I procured
CH3)N+2KOH = CH3 some volatile spirit of sal-ammoniac, and having put it
coN2kona H2)"twTOK into a thin phial and heated it with a flame of a candle, I presently found that a great quantity of vapour was
The years that followed, 1849 to 1851, were prolific in discharged from it, and being received into a basin of ammoniacal discoveries. Hofmann pointed out that not quicksilver it continued in the form of a transparent and
only one atom of hydrogen in ammonia can be replaced permanent air, not at all condensed by cold.” These by its equivalent of organic radical, but that two or all the words, written by Joseph Priestley rather more than one three atoms of the hydrogen in ammonia can be likewise hundred years ago, describe the experiment by which replaced, giving rise to the secondary and tertiary amines, ammonia was first obtained in the gaseous state."
by the following simple reactions :Unacquainted with the composition of this alkaline air,
CHz) Priestley showed that it increased in volume when electric
I. CHI+H; N=HI+ H+ N sparks are passed through it, or when the alkaline air
H) (ammonia) is heated the residue consists of inflammable air (hydrogen).
CHZ) Berthollet, in 1785, proved that this increase in bulk is
2. CHI+HN =HI+CH N due to the decomposition of ammonia into nitrogen and
Ho hydrogen, whilst Henry and Davy ascertained that two
CHZ) volunes of ammonia are resolved into one volume of
3. CH31+CHZN=HI+CH / N nitrogen and three volumes of hydrogen.
CH3) The early history of sal-ammoniac and of ammonia is very obscure. The salt appears to have been brought into To these bodies the names of methylamin, di-methylEurope from Asia in the seventh century, probably amin, and tri-methylamin were given. They resemble from volcanic sources. An artificial mode of producing | ammonia in being volatile alkaline liquids or gases, which the ammoniacal salts from decomposing animal matter combine with acids to form crystalline and well-defined was soon discovered, and the early alchemists were well salts. acquainted with the carbonate under the name of Spiritus | Hitherto these compound ammonias have been chemical salis urinæ. In later times sal-ammoniac was obtained curiosities; they have, however, recently become, as has from Egypt, where it was prepared by collecting the sub- so often been the case in other instances, of great com. limate obtained by burning camels' dung.
mercial importance, and are now manufactured on a large Although we are constantly surrounded by an atmo. | scale. sphere of nitrogen, chemists have not yet succeeded in We are all well aware that the French beet-root sugar inducing this inert substance to combine readily, so that industry is one of great magnitude, and that it has been we are still dependent for our supply of combined nitrogen, largely extended in late years. In this industry, as in the whether as nitric acid or ammonia, upon the decomposi- manufacture of cane sugar, large quantities of molasses or tion of the nitrogenous constituents of the bodies of plants treacle remain behind after the whole of the crystallisable and animals. This may be effected either by natural sugar has been withdrawn. These molasses are invariably decay, giving rise to the ammonia which is always con-employed to yield alcohol by fermentation. The juice tained in the atmosphere, or by the dry distillation of the of the beet, as well as that of cane-sugar, contains, in same bodies, that is, by heating them strongly out of con- addition to the sugar, a large quantity of extractive and tact with air; and it is from this source that the world nitrogenous matters, together with considerable quantities derives the whole of its commercial ammonia and sal- of alkaline salts. In some sugar-producing districts the ammoniac.
waste-liquors or spent-wash from the stills-called vinasses Coal, the remains of an ancient vegetable world, con- in French-are wastefully and ignorantly thrown away, tains about 2 per cent. of nitrogen, the greater part of instead of being returned to the land as a fertiliser, and which is obtained in the form of ammonia when the coal | thus the soil becomes impoverished. In France it has undergoes the process of dry distillation. In round num- / long been the custom of the distiller to evaporate these bers two million tons of coal are annually distilled for the liquors (vinasses) to dryness, and to calcine the mass in a manufa&ure of coal gas in this country, and the ammo- reverberatory furnace, thus destroying the whole of the niacal water of the gasworks contains the salt of ammo. organic matter, but recovering the alkaline salts of the nium in solution.
beet-root. In this way 2000 tons of carbonate of potash According to the most reliable data 100 tons of coal are annually produced in the French distilleries. For were distilled so as to yield 10,000 cubic feet of gas of more than thirty years the idea has been entertained of specific gravity 0-6, giving the following products, in collecting the ammonia-water, tar, and oils which are tons :
given off when this organic matter is calcined, but the Gas. Tar. Ammonia Water. Coke.
practical realisation of the project has only quite recently 22.25 8' 5 9 ' 5
5 975 average. | 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.
I and sagacious labours of M. Camille Vincent, of Paris.
New Chemical Industry.
March 14, 1879. The following is an outline of the process as carried | distillation of wood) by containing in addition methyl out at the large distillery of Messrs. Tilloy, Delaune, and alcohol, methyl sulphide, methyl cyanide, many of the Co., at Courrières. The spent-wash having been evapo. | members of the fatty acid series, and, most remarkable of rated until it has attained a specific gravity' of 1'31, is all, large quantities of the salts of trimethylamin. allowed to run into cast-iron retorts, in which it is sub. The tar, on re-distillation, yields more ammonia water, mitted to dry distillation. This process lasts four hours; a large number of oils, the alkaloids of the pyriden series, the volatile products pass over, whilst a residue of porous solid hydrocarbons, carbolic acid, and, lastly, a pitch of charcoal and alkaline salts remains behind in the retort. fine quality. The gaseous products given off during the distillation are The crude alkaline aqueous distillate is first neutralised passed through coolers, in order to condense all the por. by sulphuric acid, and the saline solution evaporated, tions which are liquid or solid at the ordinary temperature, when crystals of sulphate of ammonia are deposited ; and and the combustible gases pass on uncondensed and these, after separating and draining off, leave a mother. serve as fuel for heating the retorts.
liquor, which contains the more soluble sulphate of tri
methylamin.. During the process of concentration, Fig. I. .
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 tri. methylamin, when heated to a temperature of 260°, de. composes into (1) ammonia, (2) free trimethylamin, and (3) chloride of methyl.
3NMe,HCI=2N Mez+NH, +3MeCl. 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 pro. ducing 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 com. mon 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 1'738. 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 fame, tinged at the edges with green,
yielding carbonic and hydrochloric acids. Under pressure APO QI0no
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 liquid portion of the distillate is a very complex the liquefaction can be readily effe&ed, and the collection mixture of chemical compounds, resembling in this respect and transport of the liquefied chloride can be carried on the corresponding product in the manufacture of coal-gas. without danger. Like this latter, the liquid distillate from the spent-wash The following table shows the tension of chloride of may be divided into
methyl at varying temperatures :1. The ammonia water.
At oo the tension of CH CI is 2.48 atmospheres. 2. The tar.
4'11 The ammonia water of the vinasse resembles that of the coal-gas manufacture in so far as it contains carbonate, sulphydrate, and hydrocyanide of ammonia ; but it differs !
6.50 from this (and approximatęs to the products of the dry
From these numbers we must of cuurse subtract i to use, as they can be simply constructed, and as the vapour obtain the pressure which the vapour exerts on the con- and liquid do not attack metal and are non-poisonous, and taining vessel.
as the frigorific effects which it is capable of producing As a means of producing low temperatures chloride of are most energetic. methyl will prove of great service both in the laboratory The second and perhaps more important application of and on a larger industrial scale. When the liquid is methyl chloride is to the manufacture of methylated allowed to escape from the receiver into an open vessel, colours. it begins to boil, and in a few moments the temperature It is well known that rosanilin or aniline-red, C20H19N3, of the liquid is lowered by the ebullition below – 23°, the yields compounds possessing a fine blue, violet, or green boiling-point of the chloride. The liquid then remains colour, when a portion of the hydrogen has been replaced for a length of time in a quiescent state, and may be by the radicals methyl or ethyl, and the larger the proused as a freezing agent. By increasing the rapidity of portion of hydrogen replaced the deeper is the shade of the evaporation by means of a current of air blown violet which is produced. Thus we have triethyl rosanilin through the liquid, or better by placing the liquid in con. or Hofmann's* violet, C20H16(C2H5)3N 3. nection with a good air-pump, the temperature of the By replacing one or two atoms of the hydrogen of liquid can in a few moments be reduced to -55°, and I aniline by methyl and by oxidising the methyl anilines large masses of mercury easily solidified. The construc thus obtained, Charles Lauth obtained fine violet colours, tion of a small freezing machine employed by M. Camille whilst about the same time Hofmann observed the proVincent is shown in Fig. 2. It consists of a double-cased duction of a bright green colouring matter, now known copper vessel, between the two casings of which the as iodine green, formed during the manufacture of the Fig. 2.
violet, and produced from the latter colour by the action
of methyl iodide. 71
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 esta. blishing a cheap method by which perfectly pure chloride of methyl can be obtained, and thus rendering the pro. cesses of the manufacture of colours much more certain
than they have been hitherto. BONAFOUX
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 methyl chloride (a) is introduced. The central space (M) copper turnings into the hot liquid. On pouring the mixis filled with some liquid such as alcohol, incapable of
ture into alcohol, the violet colour is well seen. solidification. . The chloride of methyl is allowed to enter
In reviewing this new chemical industry of the beet. from the cylindrical reservoir by the screw tap (B) and
root vinasses, one cannot help being struck by the know. the screw (s) left open to permit of the escape of the gas.
ledge and ability which have been so successfully expended As soon as the whole mass of liquid has been reduced to
by M. Camille Vincent on the working out of the processes. a temperature of – 23°, ebullition ceases, the screw (s)
Here, again, we have another instance of the utilisation may be replaced, and if a temperature lower than -23°
of waste chemical products and of the preparation on a be required the tube (B) placed in connection with a good | large scale of compounds hitherto known only as chemical air-pump. By this simple means a litre of alcohol can
rarities. be kept for several hours at temperatures either of – 23°
All those interested in scientific research must conor - 55°, and thus a large number of experiments can be
gratulate M. Camille Vincent on this most successful performed, for which hitherto the expensive liquid nitrous
issue of his labours. oxide or solid carbonic acid was required.
M. Vincent has recently constructed a much larger and The Spottiswoode Testimonial.- The Committee . more perfect and continuous form of freezing machine, in appointed to receive subscriptions to present a bust of which by means of an air-pump and a forcing-pump the Mr. William Spottiswoode, Pres. R.S., to the Royal Instichloride of methyl is evaporated in the freezing machine tution as a testimonial of his valuable services as its and again condensed in the cylinders. - This enlarged Treasurer and Secretary successively, have engaged Mr.
form of apparatus will probably compete favourably with Richard Belt as the sculptor. ... thc ether, and sulphurous acid, freezing machines now in
* Hofmann, Proc. Rov. Soc , xiii., 13, 1863. ..
Action of Nnclei.
CHEMICAL NEWS, 110
March 14, 1879. NOTE ON
ON THE ACTION OF NUCLEI, &c. VICTOR AND CARL MEYER'S NEW METHOD OF
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 A GREAT number of processes for determining vapour
own." Is it not possible for a scientific man to be anxious densities have been published during the last few years,
only for the truth? That I was so will appear from the but by far the greater number of them have only been used
fact that Mr. Grenfell showed me some of his experiments, by their inventors, and none of them have entirely super
and although I did not agree with his conclusions, while seded the processes of Gay-Lussac and Dumas for deter
he decidedly opposed mine, I asked him to draw up an minations at ordinary pressures.
account of them for the Royal Society, and I promised to The last process of Victor and Carl Meyer* has, how.
present his paper, which I accordingly did, and it was ever, had a different fate, and from the moment it was
read and printed in the Proceedings. published excited the earnest attention of chemists and
My object in repeating Mr. Grenfell's experiments was physicists. In simplicity and accuracy it leaves nothing
to see whether any fresh hint could be gathered from them. to be desired, and it possesses the great merit of being
I never once mentioned my own theory; but I gained this available at all temperatures up to the softening point of
useful piece of information, viz., " that supersaturated glass; and, doubtless, if the apparatus were constructed
saline solutions behave differently among themselves and in metal its range of usefulness would be still further
to different bodies under varying atmospheric conditions ;'' increased. In fact, MM. Victor and Carl Meyer may be
and that "an oil, &c., introduced into the closed flask, as congratulated upon having devised a method of deter
in M. Viollette's and Mr. Liversidge's experiments, may mining vapour-densities which will probably supersede
be inactive, while under the other conditions the same oil all those in use at the present time for ordinary pressures.
may be active." I give abundant proof that this is so in Amongst its other merits it can be constructed by any
a subsequent paper, which Mr. Grenfell does not appear one with the greatest ease with the materials which are
to have seen ; while in a third paper the powerful influence to be found in every laboratory.
of the sides of the vessel in maintaining the state of super. Having to determine the vapour-densities of two fractions
saturation is dwelt upon. of ß-lutidine, supposed to be very nearly pure, I improvised
As space is valuable in the CHEMICAL News I will not an apparatus for the purpose. In all essential features it re
follow "Mr. Grenfell in his method of minute criticism, sembled that of Victor and Carl Meyer. The glass flask c, in
which throws no light upon the question as to what are the illustration, p. 66, was, however, replaced by an iron tube
the precise conditions under which these solutions become closed at the lower end, which happened to be in the labo.
solid. Mr. Grenfell says that it is absorption that does ratory. It was charged with aniline. The long neck of the
the whole work. That is a fair subject for discussion; vapour flask, b, was cut off two inches below the lateral
but I must protest against the general tone of Mr. Gren: tube, a, and, the two ends being brought close together,
fell's note, especially that part of it which makes me so were joined by an india-rubber tube ; the object being to
silly as not to know the simple conditions under which he give the apparatus some flexibility, and lessen the chances
conducted his experiments. In such a censure he, un. of fracture of the tube a, which had been drawn out some
consciously perhaps, includes such good observers as what too finely. These details are merely mentioned to show
Löwel, Viollette, and Liversidge, who expressly say that 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
hydrated, are incapable of determining the solidification together. In my first apparatus the funnel d was made
of these solutions. I stated in one of my early papers that as directed, but subsequent experience has shown that it
I do not agree to this, and in a paper which is now being is unnecessary, as the small tube is easily closed by an
prepared the reasons will be given more distinctly. india-rubber stopper without the necessity for enlarging In conclusion. I never said or implied that Mr. Grenfell the aperture.
denied the result of the well-known lecture table experi. A preliminary experiment was made with water with
ment with Glauber's salts. I may also add that the early the following result:
observers saw the objections to cotton wool for closing the S= 0.0207 grm.
flasks, and that I am not so careless as to allow crystals t = 13:19
of the salt to exist in the necks of my flasks before making B=758.8 m.m. (corrected.)
Highgate, N., March 8, 1879.
LARGE CRYSTAL GROWING.
By CHARLES W. QUIN.
Boiling-point, 164o B oiling-point, 164° to 1650. WHEN I was a student I was much given to large crystal
growing. My great difficulty was to guard against sudden t = 12°
rises in temperature, which generally had the effect of B=761'5 m.m. (corrd.) 76145
causing the growing crystal to be partially and unevenly w= 10'2
re-dissolved. To receive a continually even temperature, V= 20'0 c.c.
after many experiments I hit upon the plan of plunging D= 3.65
the beaker containing the growing crystal into the house. Experiment.
cistern, the temperature of the water in which, as I found Theory. Error.
by trial, never differed by more than 0.5° F. either way 3.65 3.65 3•699 -0*049
day or night. To prevent the solution from becoming I attribute part even of this small error to the B-lutidine
exhausted too rapidly I used to immerse in it to the depth containing traces of the next lower homologue.
of half an inch or so a crystal drainer containing a filter.
paper full of the salt to be crystallised, so that a constant * Deut. Chem. Ges. Ber., xi., 2253; CHEMICAL News, vol. xxxix.
stream of strong solution was continually descending on page 66.
the growing crystal.
Analysis of Combustible Gases. March 14, 1879. ]
PROCEEDINGS OF SOCIETIES. | McLeod's apparatus is used, and proves that the sensi.
tiveness of the apparatus depends on the length of the
pressure tube above the top of the eudiometer tube. With CHEMICAL SOCIETY.
the old method of introducing a large excess of oxygen in
order to moderate the violence of the explosion, this long Thursday, March 6, 1879.
eudiometer tube was necessary to contain the large quan.
tity of gas introduced. On the other hand, to lengthen Dr. J. H. GLADSTONE, F.R.S., President, in the Chair. the pressure tube would render it unwieldy from its great
length, so that with the old method of introducing a large AFTER the announcement of visitors, confirmation of e
mation of excess of oxygen the relative lengths of the pressure and
haleudiometer tubes must remain unaltered; but by employing minutes, &c., the following certificates were read for the first time :-F.A. B. Jewson, T. H. Walker, W. E. Blythe. I
the reduced tension method proposed by the author, and The list of Officers proposed by the Council was then read
in which only the theoretical quantity of oxygen required from the Chair.
has to be introduced, the necessity for such a long eudio
meter tube is obviated. The author, therefore, has The President then called on Mr. G. Artwood to read
shortened the eudiometer tube to about 500 m.m., retaina paper “On the Quantitative Blowpipe Assay of Mer.
ing the original length of the pressure tube, and finds cury. The author divides compounds to be assayed into
that the apparatus has gained in delicacy and is still three classes. Class A, containing metallic mercury, sufficiently large for all substances. The next modifica. cinnabar, tiemannite, suboxide, protoxide, and mixed
tion introduced by the author is the substitution of a steel sulphides. Class B, calomel, corrosive sublimate, and block with a three way steel tap for the glass taps coniodide of mercury. Class C, amalgams of gold, silver, necting the barometer tube, eudiometer tube, and pressure copper, lead, zinc, tin, &c. Class A.--I0 to 20 grains of bottle. The tubes are fixed and held tight in the steel the ore, finely powdered and passed through a sieve, 1 block by india-rubber rings, screwed down by means of 2000 boles to the linear inch, are mixed with 5 to 10 times steel collars. Flexibility and absolute tightness are thus their weight of powdered litharge and distilled over a
secured. As regards the steel tap the author has had no spirit-lamp in a small glass retort, if inches long and
difficulty in keeping it perfectly tight; the three ways are 7 inch in diameter. To this retort is fitted by means of!
gouged out on the surface of the tap and are not bored. a cork a glass tube, slightly curved, 2 inches long, and The use of the steel plates connecting the eudiometer Sths of an inch in diameter. The end of this tube dips
and laboratory tubes has been abandoned, and a hollow under water contained in a small porcelain crucible.
glass tap substituted, which is so bored that the tubes The operation lasts only a few minutes. The mercury is
can be washed out. The mercury trough is made move. carefully collected from the glass tube and crucible. The
able by an ingenious mechanical arrangement. The retort is broken up and its contents carefully powdered
supply of water to keep the apparatus at a constant temand examined by a lens for mercury. The globules are
perature is brought in at the top of the barometer tube ; the then united by gently warming under water, and the dry exit is at the bottom, and a syphon arrangement is added mercury weighed. Class B.-A quantity of the finely
| to ensure a thorough mixing of the water round the top powdered ore, equal to 10 grs., is mixed with three times its
| of the eudiometer tube. The little windlass has been volume of oxalate of potash and one volume of cyanide of
modified so that it can be worked with one hand. In potassium. The apparatus closely resembles that used / conclusion the author gives details as to the management in class A, but the retort has a small bulb. Class C.
of a gas analysis with the modified method and apparatus; These amalgams are sometimes powdered with difficulty, I a drawing of the latter accompanies the paper. and it is often advantageous to add a known weight of Prof. FRANKLAND complimented the author on the pure mercury, so as to render them semifluid before I ingenuity displayed and the success achieved in his paper. distilling. Io to 30 grs. of the amalgam are usually taken at the first mention of the return to a use of the steel for an assay. A turned steel retort is used for distillation,
stopcock he must confess that he had almost shuddered. which is effected in a small charcoal furnace heated by a
Twenty-five years ago when glass stopcocks were a blowpipe flame; the head of the retort is accurately ground
luxury these steel taps constituted a never-ending source to fit over the body. The retort including the cup and
of annoyance. After a week's work a leak almost always cap is i inch high; the neck of the cap is 2 inches long.
occurred, which necessitated a prolonged and careful The paper contains full-size illustrations of the different
grinding. This might be due to the fact that the tap was retorts, &c., which are made by Casella. The author has
made of cast-iron and the plug was bored. The method had much experience, and states that most accurate
of exploding gases with almost theoretical quantities of results can be obtained with the above apparatus.
oxygen was a decided step in advance. The shortening The next paper was read by Mr. J. W. THOMAS. “On of the eudiometer tube and the increased sensitiveness some points in the Analysis of Combustible Gases and in thereby attained seemed to him also most important the Construction of Apparatus." In 1874 the author improvements. He would like to ask Mr. Thomas how noticed that when a small quantity of marsh gas was mixed the bursting of the flexible tube connected with the with about three times its volume of oxygen and rarefied pressure bottle was obviated. All plans that he had until the pressure was 160 m.m. no explosion took place ; tried had ultimately failed (winding tape, tubing with similarly when mixed with twice its volume of oxygen canvas in it, &c.). under a pressure of 130 m.m. the spark did not ignite the Dr. Wright suggested that the tubing should be coiled mixture. It soon became evident that the cooling effect round with bell-wire. of the walls of the eudiometer was the chief agent in Prof. McLeod said that a plan which answered very modifying the force of the explosion. It was also noticed well was to bind the tube with tape, and cover that with that the expansion of a gas to twice its volume lessened sheet india-rubber to prevent contact of the tape with the force of the explosion to a greater extent than the potash, &c. He had been much struck with the success addition of an equal volume of inert gas at the initial with which Mr. Thomas had used the theoretical quantity pressure. The author accordingly made estimations with of oxygen without fracturing the eudiometer. In the old marsh gas and hydrogen, using nearly the theoretical apparatus the difficulty was not so much to keep the steel quantities of oxygen and a pressure of 160 to 170 m.m., i tap tight as to make a tight cement joint between the and found that perfe&ly accurate results were obtained, block and the glass tubes. whilst the safety of the eudiometer tube was not in the Mr. Hart suggested that the india-rubber tubing should least endangered. The author then proceeds to point be wound with tape soaked in glue containing bichromate out the errors which creep in when the long (800 to l of potash. On subsequent exposure to light a compound goo m.m.) eudiometer tube of Frankland and Ward's or was formed unattacked by acids and alkalies.