Scientific American Supplement, No. 401, September 8, 1883
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Various >> Scientific American Supplement, No. 401, September 8, 1883
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In comparing the last results of our experiments with those that we had
obtained previously, we saw, for example, that the camphor moved in the
test glasses at a level that was notably higher than that at which its
gyration took place the day before, or the day before that. And yet we
had always used the same vessels, the same water, and particles detached
from the same lump of camphor.
To what, then, could be due the difference observed between the two
levels at which we had, in the first and last place, seen the
camphor execute its movements? In the absence of any answer that was
satisfactory, we finally suspected that the difference that we had
noticed was ascribable to the fact that, after the numerous washings
that the apparatus had been submitted to in having water poured into
them to repeat the experiments, they had gradually been freed from
impurities of whatever nature they might have been, and which, unbeknown
to us, might have soiled their sides.
Starting with this idea, which was as yet a hyphothetical one, we began
to wash our hands, glasses, etc., at first with very dilute sulphuric
acid, and then with ammonia. Afterward we rinsed them with quantities of
water and dried them carefully with white linen rags that had been used
for no other purpose; and finally we plunged them again into very clean
water. We thus cut the Gordian knot, and were on the right track.
In fact, on again repeating Mr. Dutrochet's experiments, with that
minute care as to cleanliness that we had observed to be absolutely
necessary, we saw crumble away, one after another, all the pieces of
the scaffolding that this master had with so much trouble built up. The
camphor moved in all our vessels, of glass or metal, and of every form,
at all heights. The immersed bodies, such as glass tubes, table knives,
pieces of money, etc., had lost their pretended "sedative effect" on a
pretended "activity of the water," and on the vessels that contained
it. The so-called phenomenon of habit "transported from physiology into
physics," no longer existed.
The likening of the apparatus employed to obtain motions of camphor
upon water, with the entirely physiological apparatus by means of which
nature effects a circulation of the liquid contained in the internodes
of _Chara vulgaris_, had proved a grave error that was to be erased from
the science into which it had been introduced by its author with entire
good faith. The true cause of _life_ had not then been unveiled, and the
new agent designated as _diluo-electricity_ vanished before the very
simple and authentic fact that camphor moves rapidly upon the surface
of very pure mercury, in which no one would assuredly suppose that that
volatile substance could dissolve.
Mr. Dutrochet attaches great importance to the manner in which the water
is poured (with or without agitation) into the vessel with which
the experiment is performed. The matter is in fact of little or no
importance, and to prove this, it is only necessary to employ a test
glass (see figure) provided with a lateral tube, A, that terminates in a
lower tubulure, B, above which there is a contraction, C. Upon pouring
water into the lateral tube until the level reaches D, and placing
a particle of camphor on its surface, the camphor will be seen to
continually move about, even when the liquid has reached the upper
edge of the vessel. To reduce the level to various heights, it is only
necessary to revolve the tube in the cork through which it is fitted to
the tubulure. In proceeding thus, agitation or _collision_ of the water
is avoided; and yet if the test glass is very clean, the camphor will
continue to move at every level of the water.
But, some one will doubtless say, how do you explain the stoppage in the
motions of the camphor on the surface of water contained in vessels that
are not perfectly clean? Before answering this question, let us say in
the first place that the cause of the motions under consideration is due
to nothing else but the evaporation of this concrete oil--to effluvia
that escape from all parts and that exert upon the body whence they
emanate a recoiling action exactly like that which manifests itself in
an aelopile mounted upon a brasier, or, better yet, in the explosion of
a sky-rocket. A portion of these camphory vapors, as well as a small
portion of the camphor itself, dissolves in the water and forms upon its
surface an oily layer which is at first very slight, but the thickness
of which may increase in time until it becomes (especially if the vessel
is narrow) a mechanical obstacle to the gyration of the small fragments
of camphor that it imprisons, and whose evaporation it prevents. Now,
as this layer of volatile oil may and does evaporate, in fact, after a
certain length of time, the camphor then resumes its gyratory motions;
but there is not the least reason in the world for saying on that
account that it "has _habituated_ itself to the cause which had at first
influenced it, and that, too, in modifying itself in such a way as to
render null the influence of a cause that has not ceased to be present"
(Dutrochet, _l.c._., p. 50).
We have been enabled to convince ourself of the existence of this oily
layer of camphor when it was of a certain thickness by introducing under
the water on which it, had formed, a few drops of sulphuric ether whose
sudden evaporation produced sufficient cold to instantaneously congeal
the layer in question and thus render it perfectly visible to the eye.
The slight layer of greasy matter that habitually lines the sides of
vessels from whence no effort has been made to remove it, produces
effects exactly like those of the oil of camphor, that is to say, that
in measure as it becomes thicker it likewise arrests the motions of the
concrete volatile essence.
This is precisely what happens in a test-glass in which we see the
camphor in motion become immovable if the level of the water be raised a
few centimeters, and, more especially, if it be raised to the upper edge
of the apparatus. In its slow ascent the liquid _licks_ up, so to speak,
the oily layer that lines the inner surface of the vessel, and this
material spreads over the surface of the water and forms thereupon a
layer which, in spreading over the bit of camphor itself, prevents its
evaporation, and, consequently, its motions. The existence of the layer
under consideration cannot be doubted, since it is made to disappear by
causing the water to-overflow from the edges of the vessel, and, more
easily still, by spreading a piece of filtering paper over the liquid in
which the camphor is in a state of rest. As soon as the paper is
removed (without the water being touched by the fingers, it should be
understood), the camphor resumes its motions and afterward continues
them at all levels.
The fingers themselves, provided they are very clean, have no power to
stop the gyration. The following experiment, which is easy to repeat, is
an unquestionable proof of this.
Wash carefully the middle finger with aqua ammonia, and afterward with
plenty of water, and then dip it into a drinking glass in which a
fragment of camphor is rapidly moving, and the gyration will not be
stopped. But it will be made to stop instantly if the finger in
its natural state (that is, covered with the fatty substances that
ordinarily soil the fingers, especially in summer) be dipped into this
same glass.
_Movements of Camphor upon Mercury_.--In order to study the motions of
camphor, mercury possesses, as compared with water, a great advantage,
and that is that we can easily assure ourselves of the degree of
cleanliness of this metal by means of the condensed breath. The
vapory-deposits thereon in a uniform manner if the mercury is perfectly
clean, but forms variously shaded and more persistent spots if it is
soiled by foreign bodies But it is extremely difficult to clean mercury
completely. To do so Mr. Boisgiraud and I take distilled mercury and
leave it for a long time in contact with concentrated sulphuric acid,
taking care to often shake the mixture. Then, after removing the greater
part of the acid, we throw the metal into a vessel containing quick lime
in powder, and finally pass it through a filter containing a few holes
in its lower part.
Purified by this process, mercury not only permits of the motions of
camphor on its surface, but renders visible the traces of the vapors
that escape from it, and which resemble small tadpoles with a long tail
that are endowed with very great agility. Nothing is more curious than
to see the particle of camphor successively ascend and descend the
strongly pronounced curves presented by the mercury near the sides of
the vessel that contains it. On raising the temperature of the metal
slightly, the motions of the camphor on its surface are accelerated, and
the same effects occur with water that has been slightly heated.
The experiments that we have just called attention to show what
importance slight impurities may have upon certain results. "They
prove," says our learned colleague Mr. Daquin, "that there exists upon
polished substances an imperceptible coating of those fatty matters
which serve to-day to explain Moser's images." We find therein also a
manifest proof and a rational explanation of those grave errors into
which the presence of these fatty matters, that have hitherto been
scarcely suspected, led so clever and so distinguished a scientist as
the illustrious discoverer of endosmosis.--_N. Joly, in La Nature_.
* * * * *
CARBONIC ACID IN BEER.
We present a diagram, on exposition at the last Brewers' Convention in
Detroit, of the racking device, devised by J. E. Siebel in 1872, and
used at that time in the brewery of Messrs. Bartholomae & Roesing, in
Chicago. The object of the apparatus is to retain as much carbonic acid
in the beer as possible while racking the same off into smaller packages
from the storage vats. The importance of this measure is apparent to
every one who knows what pains are taken to preserve the presence of
this constituent in all the former stages of the brewing process. In the
method of racking off which is in present use in most breweries, the
beer is forced through a rubber hose from the cask in the store vault to
the barrels, kegs, and smaller packages in the fill room. Owing to the
excess of pressure in the beer as it enters the keg, it is evident that
a large amount of the carbonic acid gas must escape. The escape of
carbonic acid during the process of racking off is indeed so large that
even a small difference in the pressure of the atmosphere causes a
remarkable difference in this respect. It is, therefore, evident that if
a larger pressure can be maintained while racking off, a larger amount
of carbonic acid gas will remain in the beer. It is true that the
racking off will take a little longer time if done under pressure, but
this inconvenience is certainly insignificantly small, when compared
with the other labors and troubles daily undergone in a brewery, for the
sole purpose to preserve in the beer the carbonic acid in that form in
which it has been formed during the fermentation, and in which form it
has far more refreshing and other valuable properties than in any
other form in which it may be subsequently introduced into the beer by
artificial means. The apparatus designed in the accompanying cut is
calculated to artificially produce a higher pressure of the atmosphere,
at least within the keg which is to be filled with beer. For this
purpose, the beer from the store cask running through the pipe, B,
enters the keg through a hollow copper bung, fitting light into the bung
hole by means of a rubber washer. The air contained in the keg, being
replaced by the beer, is forced out by means of the hollow copper bung,
taking its course through the pipe, inscribed "Glass Gauge," until it is
allowed to escape in the standpipe, C, containing a column of water,
the height of which designates the pressure within the keg, and a
consequently increased retention of carbonic acid gas. If the keg or
barrel is filled with beer, the same becomes apparent from the beer
showing itself in the glass gauge; then the faucet, B, is closed, the
copper bung is lifted out of the bung hole, and the beer contained in
the pipe is just sufficient to completely fill the keg, which is then
bunged up, while the apparatus is transferred to the next keg. Should
the attendant carelessly neglect to close the faucet in proper time, the
surplus beer will not necessarily be wasted, but will be collected in
the vessel, D, whence it can be drawn off through e.--_Chemical Review_.
[Illustration]
* * * * *
ON THE DIFFERENT MODIFICATIONS OF SILVER BROMIDE AND SILVER CHLORIDE.
Hermann W. Vogel has made a comparative study of the properties of
silver bromide, obtained by precipitation in an aqueous solution of
gelatin, and those of the same compound prepared by precipitation in an
alcoholic solution of collodion. In 1874 Stas called attention to six
modifications of silver bromide. One of these, granular bromide of
silver, obtained by boiling the flocculent precipitate for several days
with water, he stated, was the most sensitive to light of all substances
known; exposure for two or three seconds to the pale blue flame of a
Bunsen burner being sufficient to blacken it. Important as this fact was
for photographers it was not applied for years, and it was only in
1878, when, it having been found that silver bromide precipitated in
a gelatine solution and boiled for several hours becomes much more
sensitive to light, that the remarks of Stas was recalled. Today these
observations have become of the greatest importance to practical
photography. They have led to the preparation of the silver bromide
gelatin emulsion and the silver bromide gelatin plates, which are twenty
times more sensitive than the silver iodide collodion plates, and have
become indispensable when impressions are to be taken in a dim light.
The extraordinary sensitiveness of silver bromide in gelatin seemed the
more remarkable since it was known that silver bromide in collodion is
only moderately sensitive. The explanation was sought for in various
directions, but as the result of numerous investigations it appears
that the chief cause of the difference is the presence of different
modifications of silver bromide. From a consideration of the work
already done on the subject, Vogel suspected that silver bromide
precipitated in an aqueous colloidal liquid would have notably different
properties from silver bromide precipitated in an alcoholic colloidal
solution. Silver bromide was prepared in many different ways. Emulsions
were made in bromide solutions containing gelatin or collodion (the
former aqueous, the latter alcoholic), some with the aid of heat, others
without. Part of the emulsion was then poured upon plates kept at a
moderate temperature and dried. The remainder was boiled or treated with
ammonia before being applied to the plates. He also precipitated silver
bromide in dilute gelatin or collodion solutions, allowed it to settle
completely, washed the precipitate, and mixed it with a new portion
of gelatin or collodion before applying it to the plates. Finally he
precipitated pure silver bromide, in the absence of all colloids, by
means of pure aqueous or alcoholic solutions of bromides and attempted
to bring this upon plates, using gelatin or collodion as a cement.
The result of all these experiments is that there are essentially two
modifications of silver bromide, the one being obtained by precipitation
in aqueous, the other in alcoholic solutions. The first, on account of
the position of the maximum of sensitiveness for the solar spectrum, he
calls blue sensitive, the other, for the same reason, indigo sensitive.
It is of no consequence whether the aqueous or alcoholic solution in
which the silver bromide is formed contains gelatin or collodion, or
whether the precipitation is effected with excess of bromide or of
silver nitrate. It makes no difference whether the solution is hot or
cold, or whether the silver bromide is treated with ammonia or
whether it is boiled or not. The only necessary condition is that in
precipitating indigo sensitive silver bromide the solutions must contain
at least 96 per cent of alcohol. From aqueous alcoholic solutions blue
sensitive silver bromide is precipitated.
Besides the difference of sensitiveness toward the solar spectrum, these
modifications of silver bromide exhibit other characteristic differences
in properties which indicate beyond a doubt that they are two
essentially different modifications of the same substance. Among these
are, 1st. Their unequal divisibility in gelatin or collodion solutions.
The indigo sensitive silver bromide cannot be distributed through a
gelatin solution, while the blue sensitive modification does so very
readily. 2d. Their unequal reducibility; the blue sensitive silver
bromide being reduced with much greater difficulty than the indigo
sensitive variety. 3d. Their different action toward chemical and
physical sensitizers. 4th. Their different action toward photographic
developers. 5th. Their different action under the influence of heat.
The blue sensitive variety if heated under water has its sensitiveness
perceptibly increased, while the other is not changed by such treatment.
A direct transformation of one modification into the other has not yet
been accomplished. The effect of the light upon these substances is
incipient reduction, and we might hence suppose that the more reducible
indigo sensitive variety would be the more sensitive to light. But
this is not the case, because it is not chemical reducibility, but the
absorption power for light that is of the greatest importance. Now the
blue sensitive silver bromide has a greater absorption power than the
indigo sensitive variety, and hence its greater sensitiveness. Silver
chloride prepared by methods similar to those used in making the two
forms of bromides was also found to exist in two modifications. One is
designated as ultra violet sensitive, the other as violet sensitive
silver chloride.--_Amer. Chem. Jour_.
* * * * *
ANALYSIS OF A SAMPLE OF NEW ZEALAND COAL.
[Footnote: Read before the Society of Public Analysts on the 28th June,
1883.]
By OTTO HEHNER
Some discussion having recently taken place as to the value of New
Zealand coal as a fuel, the following results of a somewhat full
analysis may be worthy of being placed on record.
The sample to which the results refer consisted of large brownish
black lumps, many of which showed woody structure; the fractures were
conchyloid, the surface shiny and highly reflecting. It was interspersed
with a considerable amount of an amber colored resin. When powdered it
appeared chocolate brown. It burned readily, the flame being bright and
very smoky. Its ash was light and reddish brown.
It consisted of--
Water (loss at 212 deg. F.) 20.09
Organic and volatile matter 75.19
Ash 4.72
------
100.00
The organic and volatile constituents had the following percentage
composition--
Carbon 71.26
Hydrogen 5.62
Oxygen 21.58
Nitrogen 1.06
Sulphur 0.48
------
100.00
The ash was composed of--
Silica 27.26
Alumina 26.48
Oxide of iron 12.98
Lime 20.19
Magnesia 3.42
Sulphuric acid 9.47
Alkalies and loss 0.20
------
100.00
From these figures the composition of the coal itself calculates as
under--
Water 20.09
Carbon 53.58
Hydrogen 4.23
Oxygen 16.23
Nitrogen 0.80
Sulphur 0.36
Silica 1.29
Alumina 1.25
Oxide of iron 0.61
Lime 0.95
Magnesia 0.16
Sulphuric acid 0.44
Alkalies 0.01
------
100.00
One ton furnished 8,458 cubic feet of gas and 8 cwt. of coke.
The very high proportion of water contained in the sample is very
remarkable. It was so loosely combined, that even at ordinary
temperature it gradually escaped, the coal crumbling to small pieces.
The large amount as well as the high percentage of oxygen characterize
the so called coal as a _lignite_, with which conclusion the physical
characters of the sample are in perfect harmony.
The resin to which I have referred has not been further analyzed. It was
found to be insoluble in all ordinary menstrua, such as alcohol, ether,
carbon disulphide, benzene, or chloroform, and neither attacked by
boiling alcoholic potash nor by fusing alkali. On heating it swells up
considerably and undergoes decomposition, but does not fuse.
The coal may be valuable as a gas coal and for local consumption, but
the large proportions of water and of oxygen militate against its use as
a steam producer, only 58 per cent. of it being really combustible.
* * * * *
DETERMINING MANGANESE IN STEEL, CAST IRON, FERRO-MANGANESE, ETC.
By E. RAYMOND.
The method in question is recommended as easy, expeditious, and
accurate. It consists in precipitating all the manganese in the state of
peroxide, dissolving it in a ferrous solution so as to bring back the
manganese to the manganous slate, and determining volumetrically, by
means of potassium permanganate, the quantity of ferrous salt which
has been converted into ferric. The method of rapidly precipitating
manganese peroxide is peculiar. If we act upon cast-iron or steel with
nitric acid and potassium chlorate in certain proportions, and boil
the mixture, the manganese is completely precipitated in the state of
peroxide insoluble in nitric acid, but retaining a small quantity of
ferric oxide. Suppose that we have a sample of steel or manganiferous
cast-iron containing less than 7 per cent of manganese. Three grammes
are treated in a small flask with 40 c. c. of nitric acid, of sp. gr.
1.20, added little by little. The liquid is stirred, and ultimately
heated to complete solution. It is withdrawn from the fire, and 15
grammes potassium chlorate are added, and then 20 c. c. of nitric acid
at sp. gr. 1.40. It is boiled for about fifteen minutes, until the
escape of chlorine ceases; all the manganese is found thrown down
as peroxide; hot water is added, the mixture is filtered, and the
precipitate washed with boiling water. To dissolve the manganese
peroxide thus obtained we measure exactly 50 c. c. of an acid solution
of ferrous sulphate, made up with 40 grammes ferrous sulphate to 750 c.
c. water and 230 c. c. sulphuric acid (full strength). The 50 c. c. are
poured into the flask in which the sample has been dissolved, and
to which a little peroxide adheres, and it is then poured upon the
precipitate and the filter in a Berlin-ware capsule. The manganese
peroxide dissolves very readily, transforming its equivalent of ferrous
sulphate into ferric sulphate. The liquid is then diluted to 100 or 150
c. c. for the next operation. We then take a solution of permanganate
formed by the same proportions as are used in determining iron by the
process of Margueritte (5.65 grammes of the crystalline salt per liter
of water), and determine its standard exactly. By means of this liquid
we determine volumetrically the quantity of ferrous sulphate remaining
in the solution of manganese. We take then 50 c. c. of the original
solution of ferrous sulphate diluted as above, and determine the total
ferrous salt.
The difference between the two determinations corresponds to the ferrous
salt which has been peroxidized by the manganese peroxide. The quantity
of iron thus peroxidized multiplied by 0.491 gives the quantity of
manganese contained in the portion operated upon. In the case of a
steel or cast iron containing but little manganese it is convenient to
dissolve the peroxide in 25 c. c. only of the ferrous solution. Small
Gay-Lussac burettes may then be used in the titration of only 0.010
meter internal diameter, and graduated into one-twentieth c. c., which
allows of great exactitude in the determination. For a spiegeleisen
not more than 1 gramme of the sample should be taken, and for a
ferro-manganese 0.3 gramme.
* * * * *
MANGANESE AND ITS USES.
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