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the bicarbonate. The filtrate is acidified, and the chromic
acid reduced and precipitated by ammonium sulphide in
a platinum dish, filtered, washed, re-dissolved to get rid
of traces of alkali, re-precipitated, and finally weighed aa
chromic oxide.

This method, due to Baubigny, for the separation of
aluminum from chromium, is very good and convenient
if the solution be free from iron and contain but little
alumina. Careful tests have shown that if iron be present
some of it always remains in solution, while if there be
much alumina it is almost impossible to wash out all of
the chromate from the bulky precipitate with the cold
solution of bicarbonate which must be used. It must
also be noted in this connexion that a solution of iron
and chromium piepared by the Baubigny method was
made ammoniacal ; and it was proved that, while all of
the iron was precipitated, this precipitate, even after the
most careful washing with hot water, contained chromium.
Although the number of details in this process may
seem very great, experience has sbown that none of them
can safely be negleded for the purpose of shortening the
work ; if the whole process be carefully followed out the
results are very satisfadory, as shown by the following
tests on a typical magnesian rock : —

Percentage CfaO.. TiO.. BaO. PaO«.

No. I. 0*270 0*46 0*040 o*375

No. a. 0*285 o'39 O'o6o 0*385

No. 3. 0*3x7 0*46 0*055 —

No. 4. 0*280 — — —



Average 0*288



0*44



0*052



0*380



* Proc, Am, Acad,, xii., 4S5 aeq. (BuU,, No. a;, U. 8. Q. S. p. 16 seq.).



Digitized by \JIKJKJWIK^



CSMIKAIrNlWl,!
Jant s* 1891* I



Experiments on the Precipitation of Antimony.



269



The nie of lodiom nitrate for the fusions is not abso-
lutely necessary, though one is more sure of complete
oxidation if it be employed. In the analysis of chrome
ores the best results have been obtained by fusing the
finely-pulverised ore with sodium carbonate alone, but
keeping it in clear fusion for an hour. The fused mass is
treated like an ordinary silicate fusion, the silica after
weighing being volatilised by hydrofluoric acid, and the
residue, usually small, again fused with sodium carbonate,
giving a clear solution in hydrochloric acid. — Amtrican
Ch$mUal youmal, vol. xiii., p. 106.



BXPBRIMENTS ON THE PRECIPITATION OP

ANTIMONY PROM SOLUTIONS OF THE

TARTRATE OF ANTIMONY AND

POTASSIUM.*

By J. H. LONQ and H. B. SAUBR.

IM an investigation by one of us on the polarisation of
solutions of potasium antimony tartrate it was observed,
incidenuUy, that several interesting features are pre-
■ented in its precipitation by other salts, notably by
carbonates, phosphates, and acetates. We have made
this precipitation the subjed of a series of tests, the main
results of which are here given.

The tartrate used for the investigation wm purified by
Mveral crystallisations from the purest obtainable com-
mercial produd. An amount sufficient for all tests was
prepared, powdered, and preserved in uneffloresced con-
dition in several stoppered bottles until used.

Pricipitation by Sodium CarhonaU,

When an alkaline carbonate it added to a solution of
potassium antimony tartrate, a precipitate is not always
formed immediately. In fa^, by working at a low tem-
perature, and mixing the solutions slowly more than the
total amount of carbonate necessary for complete precipi-
tation mav be added without producing even an opales-
cence. The polarisation phenomena of such a mixture
show that a chemical change of eome kind has, however,
taken place. When allowed to stand mixtures prepared
in this way gradually become turbid, but without the
escape of (50a, and in time a precipitate settles out. The
appearance of the precipiute may be very much delayed
by mixing the solutions with the least possible agitation
and by keeping the mixture in a cool place.

By boiling, of course, precipitation takes place imme-
diately, and the amount of antimony thrown down stands
in relation to the amount of carbonate used.

This precipitate is referred to in the American edition
of Fresenius Qualitative Analysis as antimonious hy-
droxide, but the composition is not given. A precipiute
having the composition SbaH405 has been analysed by
Scha&er. This corresponds to SbaO^'aHjO, or —

a(SbOOH)+HaO,
containing 74*08 per cent of antimony. In our investiga-
tions we find that the precipitate dried at zoo" has prac-
tically the composition Sba03*HaO, containing 78*4 per
cent of antimony. Slight variations in the amount of
water were, however, observed, and these seemed to
depend on the temperature and other conditions of pre-
cipitation rather toan on the temperature of drying. The
amount of antimony found was occasionally greater than
called for by tne formula with one molecule of water.

In the first series of experiments our tests were carried
out in this general manner. 5 grms. of the tartrate was
dissolved in 60 — 70 c.c. of water and cooled to 20° C.
To this solution a weighed amount of sodium carbonate,
dissolved in a small amount of water, was added, and the



« From tht Journal o/Anafytieia and Applied Chtmiitry, v., No. 3.



mixture diluted to exaAly zoo c.c. at ao^ It was then
allowed to stand 24 hours. Usually, in solutions con-
taining only small amounts of carbonate, precipitation
did not soon begin; in some solutions several hours
elapsed, but in all cases as much precipitate m formed
at all, settled out, leaving the supernatant liquid clear
before the end of the 24 hours.

When abundant enough, a portion of the precipitate
was taken for analysis, and the amount of antimony left
in solution was alto determined. This was done by con-
version into sulphide, washing and drying with the usual
precautions, and weighing in a Qooch filter. The analyses
of the precipitates in this series gave, in the mean, 78*8
per cent of antimony. The general results of the experi-
ments are given in this table.

zoo C.C. ai ao*.

Amoant of Amoant of For cent of

KSbOT. Na.COa. SbaSg from so c.c. KSbc57 taken

No. Grms. Grm. Orm. in tolntion.

z. 5 o'z z*a64 99*93

a. 5 0'3 z'078 85*22

3. 5 0*5 0*890 70*36

4. 5 0*7 07 z8 56*76

5. 5 0*9 o*5Z7 40-87

6. 5 z*a 0*369 a9*i7

7. 5 1*5 o«7C3 «3*94

8. 5 a*o 0*0493 3*88

It will be seen from a consideration of- the numbers of
the last column how incomplete is the precipitation
even with an excess of the carbonate. For the precipi-
tation of 5 grms. of tartrate, 07982 grm. of dry carbonate
should be required on the assumption that z molecule of
carbonate is sufficient for 2 of tartrate. But with these
amounts, the table shows about one-half of the antimony
is still in solution. We carried out numerous parallel
tests, obtaining the same general results in all cases.
Exa^ly the same values could not be expeAed of course,
because the extent of precipitation seems to depend, not
only on the amount of carbonate aad the temperature, but
on the manner of mixing the solutions, and whether they
are much shaken or little. As exj>lained above, we avoided
agitation as far as possible in this series of tests.

The precipitation of antimony takes place here without
the liberation of COa» and possibly according to this
equation —

2KSbOC4H406+aNaaCOs+aHaO-

B2KNaC4H406+Sb203*HaO+aHNaC03.

This equation is suggested by the behaviour of the
solutions prepared by adding the carbonate, dissolved in
a definite amount of water, from a burette to solutions of
the tartrate containing 5 grms. in zoo cc. The carbonate
solutions had a strength of exadly 2 per cent, and when
run into the tartrate soluiion containing a little phenol-
phthalein, as indicator, nearly 80 c.c. wm required to
give colour instead of 40, which would be sufficient for
this equation —

2KSb0C4H406+ NaaC04+ HaO «

- aKNaC4H406 + SbaO^-HaO + COa.

From the behaviour on polarisation it is evident that a
readion takes place immediately on mixing the solutions.
The amount of rotation is very much decreased, even
without precipitation, from which it follows, apparently,
that the antimony must exist in soluble form other than
tartrate, as suggested by one of us elsewhere [American
youmal of Science, Odober, Z890). Something will be
said below as to the form in which the antimony may be
held here.

A study of the last column in the table above shows
that the antimony in solution diminishes very regularly
as the amount of added carbonate is increased. The
extent of precipitation at this temperature is much below



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gle



270 Blakesley's Method o/AJ^Ofiuri^ Powsr in Transfora^s. <^"dg)?yj^7*-



what it called for by theory. The nqct tests were made
with solutions mixed at the boiling heat.

The results are given in the following table : —
100 c,c. Mixed at xoo® C.





Amonntof


Amount of






Per cent of


Ko.


KSbOT.
Grm'i


N«j|COa.
Grm.


Sb,S


B itom 50 cc.
Grm.


KSbOX taken
in tolation.


9*
zo.
zz.


5
5

5


o*i




0*2608


20*6l


Z2.


5


x-0




0'i6x8


Z2'80



H9.


zoo c^. K4pt at zqo*" z Homr.
Amount of Amount of
KSbOT. N«,CO.. Sb.S, in so cc
Gnna. Grm. Grm.


13-
14.
15-
z6-

!2:

19-
ao.


5

5

5 •

5

5

5

5

5


0*2 z'ooa
o*5 0*5906
0*8 0*275 z
z*z o*zo95
z*5 0*0802
2*0 0*0560
3'5 o'osgi
5*0 0*0600




a5o


c^. Kipt at zoo** z Houu


az.
aa.
23.


5
5

5


o*2 0*423
0*8 o*zi7o
2*0 0*0342



Here the precipitation is much more complete than
before. Something similar is shown in another series of
tests where the solutions were mixed hot, the mixture
being diluted to zoo cc, and k^pt in boiling water one
hour. The supernatant liquid was filtered off, and after
cooling was diluted to zoo cc.

In three cases mixtures were made as before, but diluted
to 2150 cc. before Ideating one hqur in th^ water-bath.
The results are given ^low :—



Per cent of

KSbOT tUeO

in eolution.

79-23

46*70

az*74

8*69

6*33

4*42
4*66

474



8360

23* X 2

6*76

It will be seen that the results of experiments zz, Z5,
and 22 are nearly the same, and also that the amount of
antimony precipitated reaches a maximum to decrease in
the solutions containing the largest amounts of sodium
carbonate. The excess of this salt appears, therefore, to
have a marked solvent aAion, increased by heat, as
shown on comparing the results of experiments z8, Z9,
20, and a3 with experiment 8. Precipitation seems to
be least perfed in the dilute solutions as indicated by the
last tests. No escape of COa was observed here, while in
the stronger solutions made and kept hot the loss was
much less than we expeded. We found 0-3445 grm. CO2
in 25 cc. of the filtrate from No. Z9, equivalent to 94*9
per cent of the amount originally present, while in the
filtrate of No. 20 we found 97*4 per cent of the total COa.
In the strong solutions the conditions are naturally favour-
able for the retention of the gai\.

We tried to secure more perfed precipitation in hot
solutions than that shown in No. z8, but without much
success. From considerations above, thiioretically, pre-
cipitation should be completed "by addition of z*5964
grms. of the carbonate to the solution of 5 grms. of the
tartrate, but a test made with these amouotc showed as
much antimony in solution as was left in No. Z7, when
only z*5 grms. of the carbonate was taken. It is evident
from polarisation phenomena that the antimony here
present does not exist as tartrate, and the increased
amount with increase of added soda suggests the gradual
formation of antimonite, even before a maximum in the
oxide is reached.

Complete precipitation, if possjble at all, must be looked
for onl^ at very low temperatures, and a study of the
connexion between temperature, amount of soda, and
precipitation would undoubtedly be an interekting one.



PROCEEDINGS OF SOCIETIES.

PHYSICAL SOCIETY.
May 22nd, Z89Z.

Prof. W. £. Ayrton, F.R.S., President, in the chair.

Mk. F. H. Neville was eleded a member of the Society.

Mr. C. J. Woodward exhibited Dr, Schdfhbsu^s Form
of LanUm SUreoscopt.

This instrument consists of a double lantern, by which
the two pidures of a stereoscopic slide are projeded on a
screen. The two pidures are coloured complementary
tints by placing pieces pieces' of red and green glass in
front of the lenses, and each observer views the over-
lapping images through spedacles, the eyeglasses of
which are also coloured red and green. The stereoscopic
effed is very striking.

Mr. Boys stated he had tried to obtain a similar result
with the aid of polarised light, by viewing two polarised
images through NicoPs prisms. No effed was pbtained,
owing to elliptic polarisation produced by the screen, bat
he thought that if a dead gold screen haul been used
instead of an ordinary one the effed might have been ob-
tained.

Prof. Perry, P.R.S., showed A New Form of Steam
Engine Indicator,"

A galvanometer mirror is fixed excentrically to a steel
disc forming one side of a chamber communicating with
the cylinder. The pressure of the steam bulges out the
disc and causes the mirror to defied a ray of light thrown
on it in the ordinary way. A rotation at right-angles to the
former is imparted by the movement of the piston rod. The
ray of light traces oiit the diagram on a screen suitably
placed, and the complete figure is continuously visible
owing to the persistence of impressions. This indicator
possesses advantages over other forms, in being free from
errors due to ftidion, or oscillations of the springs and the
alteration of their elasticity due to temperature changes.
The errors of ordinary indicators are considerable at high
speeds owing to the ripples introduced into the indicator
diagram. If the natural period of the spring is ona-
twentieth of the time of a revolution, the diagram is &trly
free from ripples, but if it is as much as one-tenth no
amount of fndion in the indicator will prevent ripples
forming. In the new indicator, the natural period of the
disc can be made very short.

The steel discs are easily removable, and can be propor-
tioned to suit different pressures and speeds.

For experimental and teaching purposes it it
advantageous to see at once the alterations in the diagram
caused by changes of load, pressure, &c. Several diagrams
were exhibited to the meeting.

In reply to Prof. Cams Wilson, Prof. Perry sUted that
the defledion was proportional to the pressui« in tfie
cylinder within the limits any particular disc was intended
for.

Mr. Addenbrokb thought the instrument an important
improvement on its predecessors, and considered' it would
prove of great service to eledrical engineers.

Mr. Swinburne said a peculiar merit of the indicator
was that it could be permanently attached to an engine,
like an ordinary pressure gauge. He suggested the use
of a small telescope instead of the ray method.

The President thought that the instrument could be
modified so as to be useful for analysing the shape of the
curves representing alternating currents.

" On Blakesley*s Method of Measuring Power in TranS'
formers," By Prof. Perry, F.R.S.

This paper refers to the supposed error in Mr.
Blakesley*s formula, due to the fad that transformers
show magnetic leakage. The proofs of the formnla
hitherto given haye been obtained by treating the cq tia-



Digitizedby



Googk



10005^1891. I



Coal and What We Get prom %t.



271



tiont in the manner first adopted by Dr. Hopkinson. On
this tjrttem the readions of the primary and secondary
correntt are represented by the equations —

RxCx + p13^ o = RaCa +



V -



dt



S^:



di



where P and N are respedively the turns on the primary
and secondary coils, and N is the magnetic flux between
the coils. Here it is assumed that there is no magnetic
leakage, and the author thinks that on this account the
method is inferior to the original method of Maxwell, in
which the induced ele^romotive forces are expressed in
terms of coefficients of self and mutual indudion. On
the assumption that there are no eddy currents, Maxwell's
equations are —

V=RxCx+LxCi+MCa, o=RaCa+MCx + LaCa ;

in which, although Lx, M, and La may not be constant, it
may be assumed that they are respedively proportional
to P, PS, and S if there is no magnetic leakage, and if
the amount of magnetic leakage bears a constant propor-
tion to the whole flux, the three quantities may still be
assumed proportional to each other, although M* is less
than LxLa* Prom these equations we obtain —



VC



RiCx* - Ra^CxCa+ ^^"^* CxCx.
u% L»a



Hopkinson puts down the last term as zero, but owing to
the very rapid rate at which Cx changes, the iMt term is
very hnportant, eve n thou gh M may be but a small per-
centage less than VLxLa* On integrating this equation,
the first two terms on the right-hand side yield Blakesley's
formula, and the last term vanishes in the integral, be
Cause, however great, the magnetic leakage may



/



CxCxtf^ - O



when taken over a period, because the fundions are
periodic.

- Mr. Blakesley's formula thus appears to hold, whatever
the magnetic leakage. The paper contains several tables
of calculations showing the efied of magnetic leakage on
Ihe value of the terms in the equation.

Mr, Blakbslby said he doubted the corredness of the
mssomption that the value of M was the same in the two
equations, and thought that the result arrived at must be
incorred.

Dr. SuMPNBR did not doubt that if the coefficients
could be considered constant, the formula was true what-
ever the leakage, but he did not consider that the a^ion
of transformers justified such an assumption. If the
formula were true it would also hold if there were eddy
currents, as these would merely produce the efied of
additional secondary coils. He had analysed Blakesley's
method by using a modification of the Hopkinson equa-
tions, and had shown that the power as estimated by
Blakesley's formula had to be lessened by the fradion re-
presented by the expression ~

fxhpfht dtdi

E -f jhp Ai dt

where A^ and As are the instantaneous values of the
primary and secondary currents, and x is such that
N^ « Ns (i + ^)« where N^ and Ns are the fluxes of
magnetism through the primary and secondary coils at
the same instant; E is a negligibly small quantity com-
pared with the rest of the denominator. In obtaining
tlus fador no Msumption whatever had been made, and
it was easy to see that if A^ and Aj could be assumed sine
fundionst and x a constant, the value of the factor X
became x simply. In only one case did X reduce to zero,
and that was when x was a sine function of the same
period as A^ and A« . He believed that in adual trani-
formers x was approximately constant.



Mr. Swinburne pointed out that the split dynamometer
was merely a wattmeter, and stated that he had trans-
formers which, owing to magnetic leakage, would indicate
an efficiency of over 100 per cent if tested by Blakesley's
method. If this method gives an efficiency of 96 per
cent, and leakage causes a drop of 2 per cen( in E.M.F.,
the real efficiency is only about 94 per cent.. He thought
that the assumption that the currents followed a sine law
was equivalent to supposing that there was no loss in
hysteresis.

The PRBSIDBNT said that no one would be more ^lad
than himself to find that Mr. Blakesley's method watf
accurate, but he could not agree with Prof. Perry that
Dr. Hopkinson was wrong in abandoning the academical
method of Maxwell.

Prof. Perry replied to the various points raised in the
discussion.

A paper on '* Current and Potential Difference AorIo-
gies in the Methods of Measuring Power,*' by Prof. W.
E. Ayrton and Dr. Sumpnbr, was postponed.



NOTICES OF BOOKS.

Th$ Romance of ScUnc$. Coal and What W$ Get from It.
A Romance of Applied Science. Expounded from thd
Notes of a Ledure delivered in the Theatre of the
London Institution, January aoth, 1890. By Raphael
Meldola, F.R.S., F.C.S., Ac, Professor of Chemistty
in the Finsbury Technical College, City, and Guilds of
London Institute. Published under the diredUon of the
Committee of General Literature and Education ap*
pointed by the Society for Promoting Christian Know-
ledge. London : Society for Promoting Christian
Knowledge, Northumberland Avenue, W.C.
Professor Meldola*s undertaking to give an intelligible
account of the successive stages in the development of
the coal-tar industry without assuming any knowledge of
chemical science on the part of the reader is undenikb^
bold. At the same time we must pronounce it at once
meritorious and signally successful. An account both
popular and scientific of one of the most interestmg and
complicated branches of industrial chemistry has been
hitherto a desideratum. The subjed is, indeed, a some-
what hackneyed one in semi-scientific ledures and aftdr
dinner speeches, but its treatment is ordinarily superficial
and even inaccurate. Some speeches even congratulate
us that we have " no longer to ransack the hemispheres
for colouring materials, but find them at our very feet."
This is, indeed, a misapprehension, f6r although coal*tar
is produced in Britain in greater quantity than in any
other country, yet its elaboration into dye- wares is carried
on only to a comparatively small extent in this, the birth-
land of the industry in question. Hence the technology
of coal-tar and its produds is to every true Briton a
** sore subjed." We cannot help asking ourselves whether
we shall ever succeed in wipmp off this stigma and in
Msuming our legitimate place with respeA to the colour
manufadure. We must never forget that thoosh pure
science is absolutely cosmopolitan, yet applied science is
more and more becoming a phase of war. Thus the
invention of artificial alizarin has been a most disastrous
event for certain distrids in the south of France. Prof.
Meldola justly says that the cultivation of the madder
plant has had to be abandoned, and that the vast tradi
of land devoted to this purpose have become available fbr
other crops. But unfortunately there is no other crop
suitable to the locality equally or more remunerative.
Had such crops existed they would have been cultivated
in preference to madder. But at present no little of the
former madder-land is lying waste. Similar is the case
with the cochineal, turmeric, safflower, &c., plantations.
Should the attempts at the synthetic produdion of indigo
prove commercially successful mdch British capital and



Digitized by VJ^^^^



gle



272



Chemical Notices from Foreign Sources.



I Cbbmical Nbws,
I Jnoe 5, 1891.



much of the finest land in India will be thrown out of use.
Hence the triumphs of organic synthesis have their
shadow- side. What is gained by one country or one
manufadure is taken from another. Hence we cannot
afford to stand by and watch the transformation which
industrial chemistnr is effeding. In self-defence we must
keep our place in the front line. Such establishments as
the City and Guilds of London Institute are as essential
to our safety as are our cruisers and torpedoes. The only
misfortune is that in obedience with the didates of
examinationism we have to expend both more money -
power and more brain-power in obtaining equal results
than have our rivals. There are few thoughtful men who
will not, if they open Professor Meldola's book, read it
both with pleasure and profit. The way in which seem-
ingly diitind departments of pradical chemistry are
shown to be correlated will prove, indeed, a chapter in
the " Romance of Science.*'



Fift$enth Annual Report of H$r MamtyU Inspectors of
Explosives : Being their Annual Report for the Year
X890. Presented to both Houses of Parliament by
Command of Her Majesty. London : Her Majesty's
Sutionery OfiGce.

This report is from several points of view highly satis-
ladory. The number of deaths from manufaduring
accidents is but eight, being slightly below the average
(8*x) of the past ten years. These figures are the more
important as the number of fadories, their output, and
the number of hands employed are increasing. The
vigilance of the inspedors is fairly maintained, and the
local authorities are becoming more alive to their duty in
this resped. Steps are being taken to check the illegal
pradice of storing explosives in miners' houses, which has
been too prevalent in Northumberland. It will scarcely
be believed that it has been found necessary to warn
traders against delivering explosives to young children.
At Broxbourne a child of seven was adtually sent alone to
fetch explosives from a store.



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