Arnold Bennett.

Chemical news and journal of industrial science online

. (page 11 of 88)
Online LibraryArnold BennettChemical news and journal of industrial science → online text (page 11 of 88)
Font size
QR-code for this ebook


Other phenomena occurring and observed by studious
investigators may be well explained by this progressive
increase of density, pre-eminently among them two
peculiarities — the very changeable intensity of the maxi-
mum in yellow, and different yellow adion even under
stridly normal conditions.

Whoever wishes, with the foregoing explanation on
hand, to determine the yellow and blue sensitiveness of
erythrosine plates, will find that the former never reaches
the height, numerically, stated by Dr. Vogel when the
exposure is made by hiph altitude of the sun. Far from
mid-day, or in winter-time, the proportions of bnghtness
in the sun spedrum are entirely changed. The general
sensitiveness of the plate advances them more and more
towards the red end of spedrum. When the sun stands
low, at its rise and set, the erythrosine silver plate may
triumph to a still greater extent, for then it is nearly
exclusively sensitive for yellow and red, but for no other
rays.

THE ANALYSIS OF CUPRIC BROMIDE, AND

THE ATOMIC WEIGHT OF COPPER.*

By TH£ODORB WILLIAM RICHARDS.

(CoDtinued from p. 23).

II. Final Determination.
Preparation of Cupric Bromide,
In preparing cupric bromide for the final series of experi-
ments it was decided to adopt a wholly new method,
namely, the adion of excess of bromine upon copper in
the presence of water. Pure copper was prepared from
a new source, the chemically pure sulphate from a noted
German house, by the method which has so often been
described.f The salt was freed from a possible trace of
bismuth and iron by potassic hydrate in very dilute solu-
tion, precipitated from the concentrated filtrate by sul-

* Contributiona from the Chemical Laboratory of Harvard College.
—From the Ptoctedingt 0/ the American Academy of Arts and
Sciences, vol. xxv.

f Proceedings of the A merican A cademy afArts a«i Sciences, uU.j
346 ; xxiii., 178 ; ses ante, ^



Digitized by



Googk



A nalysis of Cupric Bromide, and the A tomic Weight of Coppef. 35



dSBllMALKBWti)

Jan. ig» 1891. J

phuric acid, and after many re^crystallitations was finally
twice luccetsively decomposed by fradional ele&rolysis.
The resulting copper was a very brilliant and beautiful
substance ; after being thoroughly washed and dried at
9o^ it showed no trace of oxidation on standing three
months.

The problem of the preparation of pure bromine has
been admirably solved bv Stas,* and the method adopted
in the present case was largely based upon his, although
differing from it in several important particulars. Sixty
grms. of potassic bromide in dilute solution were com-
pletely freed from a trace of iodine by two additions of a
small quantity of bromine water, shsiking out each time
with successive portions of pure carbon disulphide until
the two liquids in the separating funnel were alike colour-
less. After evaporation the aqueous solution of potassic
bromide was mixed with pure dilute sulphuric acid and
pure powdered manganese dioxide, and the mixture was
•ubjeded to distillation from a glass retort over a water-
bath into a glass condenser packed in ice. The
manganese dioxide had previously been washed with an
aqneous solution of bromine, pure water, hot dilute sul-
phuric acid, and finally with pure water again until
neutral to litmus.

Thirty-seven grms. ol bromine thus prepared were
washed twice with water and distilled four times in two
very small flasks with long side tubes, the bulbs being
alternately packed in ice and immersed in hot water as
tbey alternately served for condenser and retort. The
neck of the one serving as the latter was stopped with a
glass rod wrapped in fine asbestos, and this bulb was
always cleaned and dried before being in its turn used as
condenser. In this way bromine may be indefinitely re-
distilled with very little escape of vapour and without the
least inconvenience.

The resulting bromine, although free from iodine, of
course still contained an impurity of chlorine, which it is
possible to remove by the solution of the whole mass in
concentrated aqueons calcic bromide. The required salt
was made bv the addition of bromine to a mixture of milk
of lime with sufficient ammonia water to prevent the
formation of oxygen salts of calcium. The clear filtrate
from this operation was evaporated to dryness, and the
^'slight excess of lime was neutralised by means of pure
hydrobromic acid. The calcic bromide thus formed was
freed from iodme in the manner described in the case of
the potassium salt, and a very small amount of the pure
produd served to dissolve all the bromine previously
made. The . intensely coloured heavy solution parted
with some of its bromine on dilution, and with nearly all
the remainder on gentle distillation.

Bromine thus prepared is absolutely free from chlorine
as well as from iodine. After being twice more distilled,
it was taken at once for the preparation of the bromide of
copper used in the final determinations of the atomic
weight. The combination of the halogen and the metal
took place in a cooled flask containing water, and after its
completion the slight excess of bromine — added to insure
absence of cuprous bromide — was expelled by gentle
evaporation to dryness in a glass dish. The nearly
normal cupric bromide was then dissolved in a small
amount of water, and the strong solution filtered through
asbestos in a perforated crucible.

All experiments hitherto tried upon the salt had led to
the conclusion that the solid alone loses bromine in the
air, the solution being perfedly stable. If, therefore, it
were possible suddenly to crystallise the salt and im-
mediately to wash and dissolve it, we might hope to ob-
tain a normal solution by a method which would insure
perfeA purity. This result was at last attained by the
concentration of the dissolved cupric bromide, barely
acidified with pure hydrobromic acid, to the consistency
of syrup—the containing vessel being left wholly undis-
turt)ed m vacuo for thirty-aix hours. Upon agitation and

* Stat'i '* Untersucbos^eD," p. 158 ; Uebergesetzt von L. Arons*
tsiO|£>eipsff.



cooling with ice, the resulting odourless, black super-
saturated solution at once cry&tallsed into a mass of
brownish green needles, which were colleded on a
perforated cnicible and washed three times with a very
little water. These needles were wholly different in form
and appearance from the black scales previously prepared :
they were undoubtedly identical with those descrioed by
Berthemot and Lowig.* The dilute solution of these
crystals deposited only a wholly insignificant amount of
the basic bromide upon standing, and this small amount
was undoubtedly formed by the rapid current of air drawn
through the Oooch crucible. After remaining for niore
than a week longer there was no sisn of further deposition,
and the pure liquid was subjeded to analysis, with the
results given below*

Uitkod of Analysis.
The copper was determined in the same manner at
before, except that in experiment 18 the crucible serving
as the negative eledrode was previously coated inside
with a thin film of copper, so that the external conditions
before and after the analysis might be the same. The
data of this experiment may perhaps make the under-
standing of the method more clear.



Exp4nmimt z8.



Ormi.



Weight of glass-stoppered flask with CuBi^

solution mgySyt

Weight of glass- stoppered flask alone • • 32*289

„ solution taken .. 61*583

Corrtdedwts
Ornnt.

Crucible with copper before analysis .. •■36*5516

ist drying crucible with additional Cu

after analysis . . . . 37*2260

2nd drying crucible with additional Cu

after analysis • . 37*22605



Gain of copper film
Corredion to vacuum



Weight of copper found

Rtsult.
Weight of copper in 50 grms. solution «
50 X 0-6744

" 61*583



0*6744
0*0000

06744



0-54755



In precipitating the bromine from new portions of the
solution, not only was the resulting silver bromide
weighed, but also the silver required to form it ; and this
last value was determined according to two distind
methods. In the first place, the weight of silver reqnired
for a given weight of the copper bromide was calculated,
and somewhat less than this amount was weighed oat
^ and dissolved in nitric acid in the manner before
described. The cupric bromide was then cautiously
added to the warm dilute solution, and the deficiency of
silver made up by very careful titration with a solution
containing one grm. of silver to the litre.t After notiqg
carefully this first value for the amount of silver required,
a slight known excess of the sundard solution was added,
and the silver bromide was washed, colleded, and weighea
upon a perforated crucible as before. The excess of silver
in the filtrate was now carefully determined by means of
a standard solution of ammonic sulphocyanide, using as
a standard of colorimetric comparison solutions containing
an equivalent amount of pure copper nitrate and small
known amounts of silver nitrate. This second method of
determining the amount of silver required to precipitate
the bromine is not so accurate as the first, but is of value

♦ Berthemot and Lowig, loc.cit. . ^ «,,«.- ,„

f For a further deacriptioo of the oMtlMd by Prof. J. P. Oook^ ses
Proutdings of tfw,Am9>ua» AemHm f^ •fJUtU OMt Sewt^mt vnk,ti»



Digitized by



Google



36



chemical Notices frotn Foreign Sourcei.



rc^mcALKiwt,

1 Jan. x6, 1891.



aa a check upon the other. The most complete experi-
ment tried is given in detail, as an example of the
method.

Exptriments 22 and 25.

Grma.

Glass-stoppered flask with CuBra solution »47*7ix
„ (, alone 2x776



Cupric bromide solution taken



25*935



Amount of silver dissolved (cor. to vac.)..
,, ,, added in titration • . • •



CorreAed wtt.
Grma.

-0-9639
o*oooz



0*9640



First valui found for required silver . . .
0'50 c.c. excess of AgNOs solution added
to filtrate. Silver present 0*0005



Total weight of silver used

Excess of silver was precipitated by 0*07
c.c. NH4SCN solution. Corresponding



silver



0-9645



0*0007



Second vaiui for required silver 0*9638

Weight of crucible + AgBr dried at 130*. . 18*2516

M » i> M "0%. 18*2516

„ Oooch crucible alone i6'5738

„ AgBr in air Z'6778

„ „ vacuo .. .. ,. .. 1-6779

Results,
Weisht of silver bromide from 50 grms. of

solution 3*2348

Weight of silver (average) for 1*8583

„ bromine in 50 erms. solution . • 1*3765
„ Br calculated from AgBr

(^'<^\ X.3766

V188007/

(To be continaed).



CHEMICAL NOTICES FROM
SOURCES.



FOREiG^



NoTS<^AlI degree* of tempermtare ere Centigrade unless otherwise
expressed.

Comftts Rendus Hehdomadaires des Seances^ detAcadhine
ies Sciences. Vol. cxi.. No. 25, December 22, 1890.

On the Ultraviolet Limit of the Solar Spectrum
accordiog to Proofs obtained by Dr. O. Simony on
the Summit of the Peak of Texieriffe.— A. Cornu.
— The results of Dr. Simony's observations are given in
the form of a diagram. The author proposes the estab-
lishment of a permanent station for astro-photography
on the summit of Mont Blanc.

A New Series of Ammoniacal Combinations of
Ruthenium derived from the Nitroao-cblorlde. — A.
joly. — The author has obtained a number of compounds,
but defers giving the description of their properties.

On the Combinations of Gaseous Ammonia with
Pbosphomt Chlorides and Bromides. — A. Besson. —
The author has verified the composition assigned by
Rose to the compound of phosphorus trichloride and dry
ammonia; vis., PClaiSNHj. He has also obtained a
definite combination of PCI5 and NH^. With phosphorus
pentabromide and ammonia there is obtained an ana*
logoas compound, PBr<,9NH3. The adion of |;aseous
hydrogen phosphide, PHsf upon phosphorus chlondes and
bromides hat alto been studied.



A Method for Obtaining Pure Phosphoric Acid
either in the Vitreous State or in Solution. — M.
Nicolas.— The author ads upon phosphates with hydro-
fluoric acid instead of sulphuric acid. The readion is so
energetic that the hydrofluoric acid must be diluted with
water and the powdered phosphate added in successive
portions. The mixture must be frequently stirred.

Coloured Readtions of the Aromatic Aminea.-^
Ch. Lauth.— This paper will be inserted in full.

New Process for Detecting the Sophistication of
Olive Oils. — R. Brul^. — The process is founded upon
the use of silver nitrate dissolved in the proportion of
25 per cent in ethylic alcohol at 9o^ xo c.c. of the oil
in question are poured into a test-tube with 5 c.c. of the
silver solution and left for about half an hour in the
water-bath. The colour of the oil is then observed :
I. Pure olive oil remains transparent and takes a fine
grass-green. 2. Pure earth-nut oil takes a reddish brown
colour. 3. Sesame takes the colour of very dark rum.
4. Colza becomes black and then a dirty green. 5.
Linseed takes a dark reddish tint. 6. Cotton seed oil
turns black. 7. Camelina becomes black; by daylight,
on inclining the tube, it presents a brick-red colour.

Vol. cxi., No. 26, December 29, 1890.

This issue is merely an account of the annual public
meeting, with the lists of the prises awarded and
proposed.



Zeitschrift fur Analytische Chemit,
Vol. xxix., Part 3.

The Determination of Zinc in Ores. — Delfo Coda.—
The author dissolves 2*5 grms. sine ore in 15 to 20 c.c of
aqua regia, evaporates to dryness, adds 15 to 20 c.c.
sulphuric acid, and heats again until the white vapours of
sulphuric acid show that all nitric and hydrochloric acid
have been expelled. If copper, cadmium, &c., are present
the liquid is diluted, and these metals are precipitated by
means of sulphuretted hydrogen and filtered off. The
filtrate is boiled until the sulphuretted hydrogen is
expelled ; if only lead is present it is sufficient to dilute the
solution with water and to filter. To the filtrate which
contains onlv iron, zinc (manganese and alkalies)
ammonia is added to neutrality, and 40 c.c. ammonia in
addition, containing ^ ammonium carbonate. The iron
falls at once without carrying zinc oxide along with it.
After the flask has become cool it is filled with water up
to 500 c.c, and filtered through a dry, folded filter.
Three portions of 100 c.c. each are taken from the filtrate,
and each is diluted to 250 c.c. Each portion consequently
contains the zinc of 0*5 grm. ore, and the solution thus
obtained is ready for titration. The standard liquid is
prepared by dissolving a known quantity of pure zinc in
4 c.c. hydrochloric acid ; the quantity of zinc should be
approximately equal to that which is supposed to be
present in 0*5 grm. of ore. The solution is diluted,
rendered alkaline with 20 c.c. ammonia, and again diluted
to 250 c.c For precipitating the zinc from the standard
liquid and from the solution the author uses a graduated
Mohr's burette, containing a 2 per cent solution of
sodium sulphide. As indicator there is used an 8 percent
solution of sodium nitro-prusside, which is placed upon a
perfedly dr^r porcelain slab in drops of about 5 m.m. each.
When the zinc has been almost perfedly precipitated in
the two solutions by sodium sulphide, the zinc sulphide is
let settle until a transparent layer appears above the
precipitate. A little of this clear liquid is taken up with
a pipette and some of it is let fall upon one of the drops
of nitro-prusside until the drop is 30 m.m. in diameter.
If the well-known red colour does not appear (which
would indicate the presence of free alkaline sulphide) i cc
of solution of sodium sulphide is added to each solution,
which is then shaken, let settle, and the operation repeated
until the red colour appears upon the tile. If one of thf



Digitized by



Google



Cbbmical News,)
Jan. 16, 1891. I



Chemical Notices from Foreign Sources.



37



'iiquids has a fainter colour than the other an attempt is
made to get the same dhade by adding quantities of one-
tenth c.c. sodium sulphide. If the known weight of sine
in the standard liquid is called a, the c.c. of solution of
sodium sulphide required to throw down the pure zinc, 6,
and those used for the solution of the ore c, then the
percentage of zinc in the ore is —



r per cent.



In order to determine the accuracy of this process the
iron precipitate was analysed after being carefully washed
with ammoniacal water. It contains not a trace of zinc,
but 3*5 per cent of its weight of ammonium sulphate.
But if no ammonium carbonate is added to the ammonia
o'lo per cent of zinc is lost.

Nitrogenous Bases in the Produ(5l8 of Alcoholic
Permentation. — E. C. Morin. — From the Comptes
Rendus.

Adtion of Air and Heat upon the Tannin of Willow
Bark.— W. Sonne and P. Kutscher.— This form of tannin
is partially decomposed if its aqueous solution is heated
or concentrated.

Notes on Kjeldahl's Determination of Nitrogen.—
Schonherr {Chemiker Zeitung) and Saugerod (Arch, de
Pharmacie) recommend the determination of the am-
monia formed by means of the azotometer. A. Devarda
recommends Jodlbauer*s modification of the original
process. Lindot (CompUs Rendus) obtains good results
with the Kjeldahl process in determining nitrogenous bases
in alcoholic liquids. Poporici prefers the Kjeldahl method
to that of Varrentrap and Will in determining nitrogen
in tobacco.

Determination of the Neutralising Power of Acids.
— F. Fuchs {Akadtmii in IVi>n).— The author employs
the adion of the acids upon the alkaline sulphohydrates.

On the Ozybenzoic Acids and on Benzoic Acid. —
Oechsner de Coninck (Chimikir Zeitung), ^Meia^ and
para-oxybenzoic acids can be determined by the cautious
evaporation of their solutions in ethyl and methyl
alcohols. Salicylic acid can be determined in their solu-
tions in ethyl and methyl alcohol, acetone, &c., by a
gradual evaporation with the aid of the water air-pump.
Meta- and para-oxybenzoic acids can be determined by the
slow evaporation of their aqueous solutions. Salicylic
acid begins to sublime between 80^ and 85*; both its
isomers require higher temperatures. Benzoic acid begins
to sublime between 45* and 50".

Determination of the Hydroxyl Group.— C. Loring,
Jackson, and G. W. Rolfe.— From the American Chemtcal
journal.

Determination of Methoxyl in Organic Com-
pounds. — S. Zeisel — The author utilises the well-
known property of the methoxyl group (OCH3) to
form iodmethyl with hydriodic acid. As iodmethyl is
decomposed by an alcoholic solution of silver nitrate
with elimination of silver iodide, we have the means for
a quantitative determination of methoxyl. Rudolf Bene-
dikt and Anton Grijssar recommend the application of
ZeisePs process for testing fats, resins, ethereal oils, &c.
They have examined an entire i>eries of ethereal oils by
this method, and calculated the values obtained as
methyl originally present. They call the percentage thus
obtained the '* methyl number,'* remarking that ethyl and
the higher alkyls appear also expressed as methyl.

A New Method for the Quantitative Examination
of Saccharine. — J. Remsen and W. M. Burton. — From
the American Chemical Journal,

Detedlion and Determinaii )n of Yolk of Egg.—
S. Bein (Beruhte der Deittsch. Chem. GeseUschoft),^S^G
page II.

Detedion of Copper in Wine. — T. Gigli (Oroii and
Chtmical CitttralblaU),'^The authpr steeps a galvanic



element (zinc and platinum) in the wine, which is first
acidified with hydrochloric acid. The plates are 8 cm.
long, o'8 cm. wide, and conneded with each other at one
end by means of a platinum wire, which also serves to
suspend the element to a glass rod. In carrying out the
test, I litre of wine is mixed with 20 c.c. hydrochloric acid
at specific gravity 1*15, the liquid is divided into 5 parts,
and an element is suspended for 24 hours in each portion.
The copper present is deposited upon the platinum.

Examination of Whiskey.— Clifford Richardson.—
From the American Chemical youmal,

A Chemical ReaAion for the Baderia of Cholera. —
It is known that cultures of the bacillus in question are
coloured red by hydrochloric acid. R. Pfeiffer (Zeii, /.
Hygiene) states that this readion is also produced by cul-
tures of another comma-bacillus, Vibrio meUchnikoff,

Examination of Beet Sugar for Inverted Sugar,
Dextrine. Ac- Ihl (Chemiker Zeitung). — The author
adds a solution of methylene blue, which is decolourised
by the impurities in question.

A Process for Deteding Colouring Matters. — Gas-
ton Dommergue.— From the Moniteur Scientifique,

The Use of the Kjeldahl- WiUarth Nitrogen Process
for Investigations on the Transformations of Matter.
— Argutinsky (Pfliiger's Archiv,),— The Kuihor is satisfied
with the rebults.

New Process for Determining Uric Acid.—
Arthand and Butte (Comptes Rendus Soc. de Biologie). —
The process is founded on the insolubility of cuprous
urate, the phosphates present being first removeid by
means of sodium carbonate.

Deteaion and Determination of Sugar in Animal
Fluids.— Fr. Schenck (Pfiuger's ^wAiv.).— The author
comes to the conclusion that glucose is capable of com-
bining with the albumen o956, in which
the maximum of the blue band is not far from X 464, and
therefore outside and beyond the ordinary visible limit of
the blue carbon band.

Professor Vogel observed two other stars with similar
Bpedra, of which the main feature is the very bright band
in the blue region, namely, Arg. Oeltzen 17681 and Lai.
X34T2. These stars are too low in southern declination
to be reached from our observatory.

Vogel places the blue band in Lai. 13412 at X 469,
which shows that it has a position similar to that of No.
4001 and of Dr. Copeland*s star. In the case of Arg.
Oeltxen Z768X, Vogel makes the band to extend through
about the entire range of refrangibility occupied by the two
positions of the blue band in the Wolf-Rayet stars accor-
ding to his measures of them, namely, from X 461 to X
470, with a maximum at the place where they would over-
lap, namely, X 466.

Let us consider the four stars with an intensely bril-
liant blue band which we have examined; in two of
them the band extends from about X 464 to X 467, and in
the other pair the band has a less refrangible position,
from about X 466 to X 471, but there is also in the case
of each pair a very faint band visible, or suspeAed, at the
position of the blue band in the other pair. Further, in
Arg. Oeltzen 17681, Vogel found the bright band suffi-
ciently long to include both positions of the band.

One suggestion which presents itself is whether these
bands, or, more corredly, these groups of bright lines,
maybe variable, so that, under certain conditions, one or
other of them becomes brilliant. Such a state of things
would reconcile our observations of +3^"* 3821 with the
earlier measures of Dr. Copeland, and, indeed, might
possibly explain, if this variability should be established,
the circumstance that so accurate an observer as Pro-
fessor Vogel did not deted, even with his smaller in-
strument in 1873, the very large difference of position of
the band in 4001 from that of the corresponding band in
the stars 4013 and 3956, which was so conspicuous in



* From the Authors. A Paper read before the Roya! Society, Dec,
iBgo,

f *' An Account of tome recent Astronomical Experimeoti at High
BlevatioDi in the Andes," Copernicus, vol. iii., 1863.



1883, and is so still at the present time. In the broad
characters of their spedra, and in their magnitudes, the
Wolf-Rayet stars have remained unchanged since the die*
covery of their remarkable spedra in 1867.

As the only dired evidence of such a variability rests
upon the change of position of the band in Dr. Copeland's
star since his observation of it in 1884, 1 wrote to Dr«
Copeland to ask if his position rested upon sufficiently
accurate measures or was arrived at by estimation only.
In reply, he says : — ** The place of the blue line (rather,
band) in D.M. +37** 3821, given in the Monthly Notlcis^
is a mere estimate to show the charader of the star.**

Whether any change of position of the band has taken
place must therefore remain at present uncertain ; but,
independently of any such dired evidence of Tariability,
the two positions of the very bright blue band, with the
suspicion of faint bands at the alternate positions, appear
to us suggestive of possible variation, especially when we
consider that the spedra of these stars consist of
numerous absorption bands and groups of bright lines



Online LibraryArnold BennettChemical news and journal of industrial science → online text (page 11 of 88)