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proved so satisfadory, both as to accuracy and rapidity,
that I have been led to adopt it in the laooratory of the
farm.

The objeA of this paper is to bring before your notice
the results of some experiments contrasting this process
with others in which (a) the total solids are estimated by
evaporation in platinum dishes, and (6) in which the fat
is determined by d\tt€t weighing in flasks after exhaustion
of the milk solids in a Soxhlet tube. A series of experi-
ments (the results of which are depided in Table III.) was
also undertaken to compare the percentages of fat ob-
tained by the use of Soxhlet and Stutzer tubes respediively,
the fat being estimated by difference. Lastly, as shown
in Table IV., the results are given of a number of conse-
cutive analyses, copied seriatim from the analyses book,

* Trans, Roy. Soc. Canada^ Section III., 2890.



which show the degree of closeness with which duplicate
assays can be made by the asbestos method, using the
Stutzer tube for the extradion of the fat.



T. Bolida

by

atbeitos method.

12-85
14-36
15 21
12-80



Tablb I.

T. lolidi

by
pUt. diih.

13-25
1473
1570
I3*i4



iDcreaie in perceotige

of t. solid! by eyap.

ia plat. dish.

0*40
0-37
049
0*34



Fint Column, — In these experiments, about 10 c.c. of
milk was weighed in the tubes containing asbestos fibre,
which had previously been dried in the steam cupboard.

The tubes, with the milk absorbed in the asbestos were
then replaced in the steam cupboard, allowed to remain
there twelve or sixteen hours (over night usually), cooled
in the desiccator, and again weighed. The temperature
of the cupboard during the operation of drying is between
85** C. and 90" C, a strong current of air passing through
the chamber.

Second Column. — The milk, about 5 c.c, was weighed
quickly into small platinum dishes. These were placed
on a water>bath for four hours (the water being in brisk
ebullition), cooled, and weighed. All the results are cal-
culated from duplicate analyses.

It will be noticed from an insped^ion of the foregoing
table that the solids obtained by drying in the platinum
dishes are from 0*34 to 0*49 per cent higher than those
obtained by the asbestos method. I am of opinion that
the results from the former method are too high, and that
the increase in the total solids may be accounted for on
one or more of the following grounds : — i. By the greater
evaporation of the milk while being weighed, owing to
the large surface of the fluid exposed. 2. By the scum which
inevitably forms not allowing the complete drying of the
milk. 3. By a probable oxidation of the fat or other or-
ganic constituents of the milk.

It may be noticed here that while the milk solids in the
asbestos are always perfedly white, those in the platinum
dishes are more or less brown, clearly showing that some
change takes place in the latter process which does not
ensue by the asbestos method.





Tablb II.




Fat


Fat


Increase in percent
age of fat by


by


by


exhaustion.


weight in flasks.


direA weighing.


3-81


389


0*08


464


472


0'08


540


^'\l





390


3-88





3*47


3-5'


004


3-95


3*97


0*02


6-01


602


0*01


4-36


440


0*04


311


316


0-05


358


3 57





3-81


384


0*03


438


4-47


0'09


4-31


434


0*03



In the first column is shown the percentage of fat ob-
tained by exhausting the solids in asbestos by means of
the Sfutzer tubes; in the second are detailed those got by
extraAing in Soxhlet tubes and weighing the fat in flasks.
Though the results obtained are very close, those obtained
by direa weighing are, in almost every instance, shghtly the
higher of the two. It will be seen, when considering the
results of Table III., that the fat obtained by difference
when using the Soxhlet is somewhat lower than when the
Stutzer is employed, and hence the differences shown in
the third column would most probably have been greater
had Soxhlet tubes been used in this series. The increased
percentage of fat may, therefore, be accounted for by the



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CtaincAL tlsw«,l

April 3« 1891. I

partial oxidation of the fat when drying in the flask on the
water-bath previous to weighing. The ether used was of
the best German manufa^re, and left no appreciable
residue on evaporation.



Adulterated Spirits of Turpentine.



161





Table III.








Total aolida,






Increase in




atbeatos method,


Fat by


Pat by


percenUge of
tat by Stutxer


specific gravity.


average of


Soihlet.


Stutxer.




duplicates.






tube.


1032*0


12*84


3-73


3-88


0*15


1033-5


1435


4*60


4-61


0*01


1033-0


152X


5*33


556


0*23


1032* I


1277


3-85


397


0*12


1032*0


II 98


3-44


347


0*03


1033*2


13*03


3*94


3*96


o*oi


1032*1


X5-3I


5*95


605


O'lO


1033*4


1371


4*33


4-35


0*02


10329


X2*II


309


308





1031*0


I2-20


3-58


3-58





1033*2


13*16


3-79


3-82


0*03


10338


13-89


435


4*34





1032*6


i3r»o


4*26


4-31


0*05



In the asbestos method, as described by Mr. Macfarlane,
Soxhlet tubes were recommended to be used for the ex-
traaion of the fat. As but two — or at most three — tubes
containing the milk solids can be exhausted by this
method at once, I was induced to inaugurate the experi-
ments detailed in the above Table (III.), which shows the
percentages of fat obtained by exhausting the milk solids
for the same length of time (four hours) in Stutzer tubes,
in which from six to eight of the glass cups can readily
be treated at once, thus effeding a saving of one-third the
time over the Soxhlet method. The results by both pro-
cesses are very close, yet it will be noticed that in nearly
every instance the Stutzer tube gives a slightly higher
percentage of fat, f.#., the extradion of the fat is more





Table IV.




Total tolldt.


Fat.


Solids other than fat.


13-42
13*43


4*31
4-31


912


12-68
12*67


3-80
3*8o


8*88


J 13-13
1 13x2


4-35
4-35


8-78


13-54
.13-57


4*20

4-22


9-35


17*23
1730


8-13
8-II


914


1 15-14
Ii5-x6


608
6*10


9*06


14-09
1407


4*61
4-58


9*49


12*24
12*27


4-03
4-04


8-22


12*70
12*68


3-85
3-85


884



complete by the Stutzer process. This fad may be
accounted for by the more frequent washing ot the solids
by the ether in the Stutzer tubes, as well probably as by
the slightly higher temperature of the ether in these tubes.
The results by the Stutzer process are therefore, I am
led to believe, the nearer to the truth of the two.

Table IV. contains the results of consecutive analyses
made in duplicate by the asbestos process, using the
Stutzer tubes for the extradion of the fat. Where the
third figure in the decimal place exceeded 5, the second
decimal figure was raised.

If it be granted that the total solids and fat can be
accurately determined by this method, an inspedion of
the above figures will clearly prove that the results are
not variable, and that when duplicates are performed no
large differences will have to be averaged in order to
arrive at the truth. Judging from my own experience, I
should say that the labour and time involved in using the
asbestos method with the Stutzer tubes are about one-
third less than when other processes are employed.



ADULTERATED SPIRITS OF TURPENTINE.

A Convenient Method for Detbctino and for
Estimating Petroleum in Spirits of Turpentine.

By SAMUEL J. HINSDALE, Fayetteville, N.C.

Put ten drops of the spirits to be examined in a (moderately
concave) watch-glass, and float the glass on about a quart
of water which has a temperature of about 170" F. If the
spirits is pure, it will evaporate and leave the glass quite
dry in seven minutes. If the spirits contains even five
per cent of petroleum, it will not have completely
evaporated in that time.

This experiment will prove the absence or presence of
petroleum in the sample.

To estimate the pirantags of petroleum, weigh a
watch-glass and put into it ten drops of the mixture, and
weigh again. Put into another glass ten drops of pure
spirits of turpentine, and float both glasses on about a
quart of water at about 170" F.

As soon as the pure spirits has evaporated, take ofl" the
glass which contained the mixture and weigh it. The
difference between this weighing and the weight of the
glass will indicate the amount of petroleum in the mix-
ture. Knowing the weight of the ten drops, the per-
centage can be calculated.

A l^nt loop of wire is convenient to place on and re-
move the watch-glass from the water.

The hydrometer will deted adulteration with benzene
or petroleum, but it cannot be used to estimate the
amount of adulteration.

The specific gravity of pure spirits of turpentine is
about 0*865.

Petroleum is the usual adulterant.



The Presence of Alcohol in Comoaercial Ethyl*
Ether.— Th. Poleck and K. Thiimmel {Archiv, der
Pharm.), — If a clear mixture of 4*5 vols, of a saturated
solution of potassium bicarbonate and i vol. of a saturated
solution of mercuric chloride is shaken up with commer-
cial ether, the mixture becomes turbid in ten to twenty
minutes, and a white amorphous precipitate separates
out. If further quantities of ether are added, all the mer-
cury is eliminated except traces, whilst the substance
which readied upon the ether is withdrawn from the mer-
curial solution. The yellow or brown colour imparted to
commercial ether on the addition of potassium hydroxide
is occasioned by alcohol. — Zeit, fur Anal, Chimii, Vol.
xxix., Part 6.



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Variation q/ Surface-tension with Temperature,



< CUBMICAL NbWS,

I April 3, Z891.



PROCEEDINGS OF SOCIETIES.

PHYSICAL SOCIETY.
March 20th, iSqt.

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

Prof. S. U. Pickering, F.R.S., read a Paper on ** The
Theory of Dissociation Into Ions and its Consequences,**

According to this theory, eledrolytes are entirely dis-
sociated into their ions in weak solutions. This dissocia-
tion was held by Arrhenius to absorb heat, and although
heat is evolved by the dissolution of h)drochloric acid,
&c., it is not maintained that dissolution evolves heat,
but that the heat absorbed by the decomposition of the
molecule into its atoms is more than counterbalanced by
the heat supposed to be evolved by the combination of
the atoms with their eledric charges. These adions the
aothor considered improbable, and thought that before
being accepted, the theory must give satisfadory answers
to the following questions :~How can matter combine
with an affedion of matter to produce heat ? Whence do
the eledric charges originate ? Why does not the
opposite eledrification of the different atoms make them
cling more firmly together, instead of dissolving the union
between them ; and why should an atom which possesses
a strong attradion for a negative charge (such as chlorine)
go to the positive eledrode during eledrolysis ?

When a dilute solution, which is supposed to contain
some gaseous molecules, is further diluted, then, accord-
ing to the theory, some of the molecules are dissociated,
and, if heat is absorbed, it follows that the dissociation,
and therefore dissolution, of the gas must absorb heat ;
yet, he said, it can be shown that in some of these cases
the dissolution of a gas evolves a large amount of heat.

The antagonism between the present and the old
eleAro-chemical theory—according to which the atomic
charges are identical with the free energy of an atom,
and are the cause of combination, not decomposition —
was commented on, as well as the disagreement between
the present theory and Clausius's view that there are a few
ions or atoms present in a liquid owing to accidental
super-heating of some of the molecules. Reasons, how-
ever^were adduced for believing that the presence of even
a few atoms in a solution to be improbable.

A communication on ** Some Points in Electrolysis "
WM made by Mr. J. Swinburne.

Considering a reversible single fluid cell, the author,
by a process of reasoning based on Carnot*8 principle and
the conservation of energy, arrives at Helmholtz equa-
tion —

JE
E B E« + ^-j-

where E is the eledromotive force, Ec the part due to
chemical adion, and the absolute temperature. Writing
the eauation in full, using suffixes n and p to denote the
negative and positive plates, it becomes —

E« -f E^ = E„c+ E^ + ^^ + 0-7^

He then shows that by having the two plates in different
vessels and heating them to different temperatures, the
Peltier effeds represented by —

e^ and $^
de d$



can be determined separately. Similarly those of a two
fluid battery might be found by arranging the jundion of
the fluids in a third vessel.

After pointing out the desirability that the condittons
under which all thtrmo-chemical data have been obtained
should be clearly stated, he proceeded to show that any
cell in which seconda^ adions occur (as, for example, if
sine oxide primarily K>nned by eledrolysis were to dis-



solve in sulphuric acid), must necessarily be non-rever*
sible. He also contended that in a secondary battery the
formation of lead sulphate on both plates is the essence of
the cells aAion, and that there is no intermediate forma-
tion of PbO.

On the subjed of so-called ** nascent*' hydrogen or
oxygen, he said that reasoning from the conservation of
energy showed that neither could exist. Taking the case
of persulphate of iron in dilute sulphuric acid, which is
said to be reduced to protosulphate by the ** nascent
hydrogen " liberated on putting a piece of metal (say
magnesium) into the liquid, he said a better explanation
of the phenomena would be that the metal dissolves if it
either reduces the metal or evolves hydrogen ; and as the
former requires less energy, the redudion takes place, and
when no reducible salt is available, hydrogen is evolved.
Evolution of hydrogen, and reduAion of the per salt, are
thus alttrnative and not consecutive adions.

Examining Dr. Lodge's views on the contad E.M.F.
between metals, he remarked that if the tendency of a
metal (such as zinc) to oxidise can produce an eledric
stress or difference of potential which prevents further
combination, adlual combination must charge the metal,
if it be insulated. A piece of sodium, however, oxidises
continuously, and therefore should become charged to an
enormous potential. As this cffcd is not known to occur,
the author suggested that the Volta effed may be due to
films of water, and in support of this view adduced the
fad that metals, when perfedly dry, do not combine with
chlorine, and that even sodium is not attacked by dry
chlorine.

In the discussion on the two papers, Prof. Pickbrins
said the idea of nascent elements had, to a large extent,
been given up by chemists, and pointed out that the fad
of one readion taking place rather than another was not
merely a question of heat energy, but that a kind of che-
mical seledion was involved.

Prof. S. P. Thompson recalled attention to the fad that
the produds of eledrolvsis depend on the E.M.F. employed
in producing it, and tnought the E.M.F. required to pro-
duce the various produds might be taken as a measure of
their affinities. He did not agree with Mr. Swinburne's
method of finding the E.M.F. of a secondary battery from
thermochemical data, for he failed to see how two similar
adions going on at the two plates of a cell could add any-
thing whatever to the E.M.F. of the cell.

The President said the questioh whether the potential
difference between two dissimilar substances was due to
oxidation or to mere contad could only be decided
by dired experiments made in a vacuum, from which all
traces of moisture and oxygen had been removed. Without
agreeing with Dr. Lodge's view on the subjed, he pointed
out that the continuous oxidation of a piece of insulated
sodium need not necessarily produce a great potential
difference, for the combination might produce heat.

After Prof. Pickering and Mr. Swinburne had replied to
the points raised, Mr. Walter Bailey took the chair, and

Prof. Perry read a note •' On the Variation of Surface-
Tension with Temperature,** by Prof. A. L. Selby, M.A.

Considering unit mass of liquid at constant volume, but
variable surface (S), and temp. (Of the author expresses the
gain of intrinsic energy due to changes of the variables by
dH + dV/ mz kdt + (/ + T)dS ; where dU is the heat
absorbed, <fW the work done on the film, k the specific
heat at constant volume, / the latent heat of extension,
and T the surface tension. This being a perfed differen-
tial, it is shown that T « c — 6/, and Tadf, c and b being
constants.

Supposing c and b to be independent of the specific
volume of the liquid, it is shown that at the critical tem-
perature < a 4* ! hence, this temperature may be deter*

b
mined by findine the surface tension at two vety difiierent
temperatures. Since, also, I ^ bt, the latent heat of ex*
tension is proportional to the absolute temperature.



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April 3, 189X. I



Action 0} Water on Lead.



163



Reasons for supposing 6 to be independent of the specific
volume are given in the paper.

Mr. Blakbsley described an effect of temperature on
surface tension which he had observed in sensitive spirit-
levels. By warming one end of the tube, even by the
hand, the bubble immediately moves towards that end.
This efifed^, which might produce considerable error in
engineering operations, was, so far as he was aware, not
mentioned in the text books.

Prof. Perry remarked that although the volume, tem-
perature, and surface of the liquid had been referred to in
the paper, pressure was not mentioned, and on this point
he enquired whether the results arrived at were true, quite
independent of the pressure.

Prof. S. P. Thompson, D.Sc, read a paper on
•• Magnetic Proof pieces and Proof Planes."

The distribution of magnetism over magnets has been
examined in various ways by different observers, but
mostly by observing the force of detachment of either
rods, ellipsoids, or spheres used as proof- pieces. In all
these cases it was, the author said, difficult to see exadly
what was measured ; for the presence of (he proof-pieces
altered the thing to be tested. The pull exerted must
also depend on the permeability of the piece used, as well
as on its shape and disposition with resped to the
magnetic circuit. He had therefore investigated the sub-
jed by finding the actual distributions by means of a fiat
exploring coil and ballistic galvanometer, both with and
without the presence of proof- pieces of various shapes
and sizes. The results show that the perturbations pro-
duced by the proof- pieces are always large, in some cases
the perturbed field about a point being four to six tfmes
the unperturbed field. In most cases, however, the ratio
of the perturbed to to the unperturbed field was constant
so long as the former did not exceed 6000 C.G.S. units.

The amount of perturbation was also found to depend
on the saturation of the magnet, and on whether it was a
permanent or an eleAro-magnet. The numbers obtained
in various experiments, and curves plotted from such re-
sults, were shown.

In conclusion, the author said that in using proof-pieces
much depended on the accuracy of the contad, but in any
case the results obtained were not very reliable. The flat
exploring coil, or magnetic proof-plane, however, furnished
a satisfaAory method of examining magnetic distribu-
tions.



NOTICES OF BOOKS.



The Action of Water on Lead, Bein^ an Inquiry into the
Cause and Mode of the Adion and its Prevention. By
J. H. Garrbtt, M.D. London : H. K. Lewis.

Tub presence of lead in the water supplied to many towns
is certainly a serious evil, and as it has not been by all
means fully understood, Dr. Garrett's contributions to the
question are exceedingly valuable. It is now clear that
if a water is fairly pure it is found to aA upon lead or dis-
solve it to a certain extent, even in the absence of an acid.
The author observed that distilled waters that were
neutral, or even very faintly alkaline, can &{k upon lead.
The lead, it would seem, derives the oxygen necessary
for its corrosion, not so much from the tree oxygen or any
other oxygenous gas existing in solution in the water, as
from nitrates and nitrites present. The quantity requisite
for adion, at least in the absence of any alkaline-
earthy carbonates, is extremely small. Its origin may be
sought ** in the decomposition of the organic matter which
such waters invariably contain.** Such nitrogenous
matter ma> possibly be converted into nitric acid by the
a^un of a bacillus. This question we agree with the
author requires further study.



A careful examination was made of the water supplied
to Mirfield by the Huddersfield Corporation. The author
remarks that in a town in which the water, as delivered
into the mains, is absolutely free from lead, it may become
contaminated by means of leaden service pipes. This is
especially the case where the water supply is intermittent.
But even if constant, as it ought on sanitary grounds to
be universally, the water from the service pipes may fall
back into the mains in consequence of interchanging cur-
rents.

We may here ask whether the mechanical ingenuity of
the age could not devise some arrangement which should
render the reflux of water into the mains impossible. The
author thinks that *' in places like Mirfield no single in-
habitant could proted himself by using an iron service
pipe.'* But what if leaden service pipes were altogether
prohibited.

The evidence colleded from the author's experiments,
which appear to have been well planned and carefully
executed, leads to the conclusion that if the water con-
tains any inorganic acid it is, in part at least, probably
nitric acid.

The author's proposed remedy lies in the addition to
the water of an alkaline carbonate, and especially car-
bonate of lime 1 This is not a welcome expedient. To
have the skin, after washing, coated with a gluey film of
lime, to find linen returned from the laundry in the same
clammy condition, to partake of vegetables hardened in-
stead of softened by boiling, are certainly a serious
grievance. If the water supply is constant, and if the
consumer takes the precaution of letting a few quarts of
water run away from the tap every morning before any
is used for drinking or cooking, the danger is reduced to the
vanishing point.

Dr. Garrett*s improvement on the ordinary method of
testing for lead in water seems very feasible. He puts
into a narrow test-tube half an ounce of the water and
one drop of hydrochloric acid ; passes into it washed HaS,
and adds half a grain barium sulphate. Shake, and set
aside. Ammonium sulphide may be used instead of sul-
phuretted hydrogen, but in series of comparative experi-
ments one and the same precipitant should always be
used.

Dr. Garrett may be c6ngratulated on the thoroughness
and the value of his researches.



Kelly*s London Medical Directory^ iSgz. London
Kelly and Co.

We have here a work filling a vacancy which had
become more and more widely felt. The compilers give
the names, addresses, qualifications, and works, if any,
of all qualified medical men in pradice in the Metro*
politan district In addition it furnishes particulars
concerning hospitals, public analysts, learned societies,
medical and scientific publications, insurance companies,
lunatic asylums, and examining bodies.

Turning firstly to the sedion on scientific societies, we
note a few defedls which will doubtless not reappear in
next year's issue. Thus there is no mention of the
Society for the Promotion of Medicine by Research, which
we hope is not defund, the South London Microscopical
Society, and the South London Entomological and Natural
History Society — a very numerous body. The anti-
scientific societies are deservedly ignored.

Turning to the medical and scientific publications we
find the names of two *' weeklies " which, to our great
regret, have ceased to appear.

A glance at the main body of this diredory, the muster
roll of praditioners will prove that the labour incurred in
its compilation must have been very heavy, and we cannot
feel surprised if a few mistakes have occurred. We wish
the publishers the success which they have so fully



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