Rodolfo Amedeo Lanciani.

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glass is never necessary. I find that it requires exposures of
about three minutes to produce negatives of tissue-preparations

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302 J. J, Woodward on the Moffnesium and

with five hundred diameters. Other powers require propor-
tionate exposure&

^he magnesium lamp used by me for this Durpose was the
two-ribbed lamp of the American Magnesium Company, (No. 2
Liberty Square, Boston, Mass.,)sold by that company tor magic
lantern purposes, price $50. The ribbon weighs about 52 cen-
tigrammes per metre, and is sold at $2.60 per oimce. Two
ounces will, with care, answer for three or four hours constant
work, and oucht to produce from twelve to thirty negatives in
accordance with the difficulties of the subjects to be represented.
The fumes of magnesia resulting from the combustion are car-
ried into a chimney five feet long, made of a spiral wirfe covered
with muslin, which terminates in a muslin oag in which the
oxyd condenses, while the draft goes on through the interstices
of the muslin. The chimney and bag are furnished by the com-
pany for $2.50.

In commenting on the above processes it may be remarked
that, for the anatomist an4 physiological investigator, the Mag-
nesium lamp affords a satisfactory and sufficient source of light
for the photography of normal and pathological tissue-prepara-
tions. The same end can be equally well or even better attained
with the electric lamp, with which also the most difficult test
objects can be satisfactorily reproduced. Where economy of
apparatus is the object, the magnesium lamp will be preferred
by ordinary workers ; but where much work is to be done, the
high price of the magnesium ribbon more than counterbalances
the cneapness of the apparatus, and the electric light becomes
the^most economical For the information of any practical
photographers who may be employed for work of this character,
I may add the foUowmg remarks on the chemical process em-
ployed in the production of the negatives from which the
appended prints were made. An ammonium and potassium
portrait collodion, rich in alcohol, was employed, developed
with the ordinary solution of iron, and fixed with cyanid of
potassium. Where it was necessary to intensify, the hydro-
sulphuret of ammonium was resorted to.

In illustration of the character of these sources of illumination
as compared with each other and with sunlight, I herewith ap-
pend tluree prints from negatives, taken with a Wales' inch and
a half, from the 6th square of a M6ller*s diatom type-plate, spe-
cially prepared for the Army Medical Museum bv that skillful
microscopist The first from N^ative 79 (new series), was ta-
ken by sunlight, with 40 diameters ; in the second, from N^a-
tive 128 (new series), the magnesium light was used, and every
thin^ else remaining the same, the distance was increased so as
to give 48 diameters ; in the third. Negative 158 (new series),
the electric lamp was em^doyed, and every thing else still re^

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Electric LighUfar PhoitMnicrography. 808

maining unaltered, the distance was increased so as to give 66
diameters. It will be understood at once, that on account of
the increase of distance, the second picture would have been
slightly less sharp than the first, and the third than the second,
had precisely the same source of light been employed ; never-
theless, in spite of this disadvantage, to which they were pur-
posely exposed, the magnesium and electric pictures are fear
superior to that taken by sunlight, and of the two the electric
is much the best. It is especially to be observed, that in the
electric picture the contrast obtained is so ereat that the objects
api)ear clearly defined on an almost perfectly white ground,
which is never the case with photo-micrographs taken with the
sun as a source of illumination.

As a farther illustration of the capabilities of the magnesium
and electric lights, I add a few photographs taken by each.

Bt thb MAorasinx Liesr.

Arachnaidiscus Ehreiibergii. Magnified 400 diameters, by
Wales* }tk Native 114 (new series.)

Small vein and capillaries^ from the muscular coat of the uri-
nary bladder of the frog. Magnified 400 diameters, bv Wales'
|th. Negative 108 (new series). This negative is taken from
preparation No. 8878, Microscopical Series, in which the blad-
der was injected with a half per cent solution of nitrate of silver,
and subsequently stained with carmine dissolved in borax.
The epithelium was then brushed off with a camel's hair pencil,
and the preparation transferred through absolute alcohol to
Canada balsam : the photograph reproduces every thing but the

Bt thb Elbotbio Lioht.

PleuTostaurum acuium. Magnified 840 diameters, by Wales'
|tL Negative 109 (new series.)

Trkeraiium favu8. Magnified 840 diameters, by Wales' {th.
Native 110 (new series),

Navicula spima. Magnified 840 diameters, by Powell and
Lealand's immersion j\ul Negative 112 (new series).

Human red blood corpuscles. Magnified 1,000 diameters, by
Powell and Lealand's immersion y^t^i- Negative 145 (new series).

Section of an epithelial cancer of the larynx. Magnified 400
diameters, by Wales' }th. Negative 162 (new series). This
negative is taken fix>m preparation No. 2277, Microscopical
Section. The print shows tne nuclei and cells of the growth
with great distinctness.

* Orammatophora marina. Magnified 2,600 diameters, by Powdl
and Lealancf s immersion yV^ Negative 151 (new senes).

[The copies of the photogra^s here referred to, sent as by Dr.
Wbodwara, surDass m peneotion and beanty any specimens of
photo-micrography we have seen. — Eds.]

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804 J. H. R L. ona Mechanical Finger for the Microscope.

Abt. XXXI. — On a Mechanical Finger for the Microscope; by

J. H. B. li.

In the Journal of May, 1866, there is a description and wood-
cut of a mechanical finger, by Mr. H. L. Smitt

There are few naked eyes, or ordinary hands, that can select,
from a mass, one of the smaller diatoms; and the engraving in
the Journal was seized upon, at once, by the writer, as aflford-
inc a promise of relief in the patient labor that had so often tes-
ted both his eye and hand. It was his good fortune to be with-
in reach of one of the instrument& It was a great help, no
doubt; and, after acquiring "the knack," it was possible to use
it But it wanted solidity, and the writer ventured to think
that it might be made firmer, if constructed with fewer parts
and joints. It was a capital idea, however, useftdly illustrated;
but not beyond improvement: so an improvement, as it was
thought, was put on paper, and sent to Mr. Joseph Zentmayer,
the well known optican of Philadelphia.

Putting aside both the improvement and the original, Mr.
Zentmayer went to work upon an entirely new system, and pro-
duced what seems to be very near perfection.

The microscope, in the writer's possession, is one of Mr. Zent-
mayer's large first class ones, though the finger can be adapted
to any other. There are three pieces: one, an independent
stage, that we will call the diatom stage, (fig. 1) supported,
above the principal stage, upon a tube that fits into a sleeve
attached to a cyunder, (fig. 2), that fits into the sub-stage. The
tube of the diatom stage is passed through the opening of the
principal stage into the sleeve, as shown in the curawing, when
its only movement, up and down, is regulated by the rack and
pinion of the sub-sti^^e. Liffht from the reflector is thrown
upon the object through the tube of the diatom stage. A spring,
S, with an ivory button, B, is attached to the diatom stage, as
shown in fig. 4, which steadies the slide as it is moved by nand
to bring different parts of it into the field.

Fig. 8 shows the third piece of the apparatus, or, really, the
only piece, so far as the finger is concerned ; the other three
pieces being necessary to hold the slide containing the diatoms,
but having, otherwise, nothing to do with the finger proper.
The drawing is of fiill size. A is a clamp secured to the prin-
cipal stage by the jaws M and the movafcle plate L, which is
tightened by the set screw D. The cylinder C passes through
the clamp resting on the shoulder T. It turns horizontafly
when not fixed by the set screw F, whose point presses in the
groove shown in the drawing. The steel rod B, surrounded by
a spiral spring, which is not shown, but which can be readily

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J, H. R L. ona Mecfianical Finger for the Microscope. 805


Fig. 3.


AaL JoDB. 8oi.~8BCOin> Sbbdsb, Vol. XLIX, No. 147.— Mat, 1870.

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806 J. H, R L. cna Mechanical Finger for the Microscope.

understood, passes through the cylinder C, the spiral holding it
up when not pressed down. Upon this rod is the steel spring, Gr,
bent as shown, carrjring at its upper and longer extremity, at
N, a cork-holder, tlirough which is thrust the needle that car-
ries the hair ; and, at its lower extremity, the guide J, passi^
through a slot on the arm K, projecting from the cylinder G.
The object of this is to counteract the rotary movement that
would otherwise be caused by the spiral spring on the rod B
when pressed downward in operating the apparatus. F is a
large milled head lowering or raising tne end of the spring N, in
focussing the point of the hair. The down pressure is applied
at I compressmg the spiral spriujg around the bar B withm the
cylinder C, and bringmg the point of the hair on the particu-
lar diatom.

A most excellent, if not an original, mode of attaching the
hair to the needle, which is thrust, eye foremost, through the
cork projecting from N, is the suggestion of a friend of the
writer. Cut a piece of thin paper into the shape of the letter
V about half an inch high ana crease it lengthwise so as to
bring the sides together. Having gummed the paper well, lay
the needle on the crease, keeping its point within the paper, and
place the hair along side of it Then closing the sides of the
V , the needle and the hair will be compres^ together at the
bottom of the crease ; and when the paper is perfectly dry the
hair can be cut with scissors to the proper length, if necessary,
and so much of the paper trimmed oflf as may not be wanted
to retain the needle ana hair in their places. The needle mav
then be forced, with a pair of fine pliers, eye foremost, through
the projecting end of the cork at an angle inclining somewhat
downward ; and, when this is done, the finger is ready for usa
The angle of the needle to the stage may be changed hj turn-
ing the cork, which is screwed into the opening at If , which has
a thread for the purpose.

The slide containing the diatoms is now placed on the diatom
stage ; the part to be examined being over the opening of the
tube, through which the light is reflected, focussed as usual,
and the particular diatom selected. The hair is then brought,
by hand, within the field of view. This is done by turning the
cylinder C, and adjusting with the pliers, if need l>e, the length
of needle and hair projecting through the cork. The set screw
E is then tightened, and the observer has, in the field, the dia-
tom in focus, and the end of the hair seen dimly, and not in
focua The screws of the principal or mechanical stage now
enable him to bring the point of the hair with mathematical

Precision just above the diatom ; when, pressing at T gently
own ward, the hair touches the diatom ; the latter, if aU goes
well, adheres to it; the diatom stage is lowered; the slide re-
moved ; the clean slide, to which the diatom is to be transferred

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Friedd and Orafts on the (hmbinations, etc 807

is put in its place ; the diatom stage raised until the hair, with
the diatom on it, is in contact, when the diatom is taken off by
the moisture that has been previously breathed upon the slida

The superiority of the contrivance here described is its sim-
plicity and absolute steadiness.

In the drawing, the position of the spring Gr with the cork-
holder N is reversed. They turn, as already described, in any
direction, horizontally.

The fiacilitv with which a diatom may "be handled," to use
the term in this connection, is one of the great advantages of
Mr. Zentmayer^s contrivance. The point of the hair may be
brought into focus along side of the diatom. Which mav then,
by using the screws of the mechanical stage, be pushed in any
direction by the finger, and separated from the mass, or, when
transferred to a clean slide, may be placed wherever required
thereon. With such an instrument may be understood the
modtis operandi by which the 892 diatoms of " Holler's Diato-
maceen platte" were arranged.

Nothing more has been attempted here, than to describe the
particular instrument But no one can understand the whole
subject, without reading the most admirable article of Mr. H.
L. Smith already referred to, and which set the writer to work
to improve, if possible, the mechanism there described. L.

Art. XXXTL — The Combinations of Silicon roith Alcoholic Radi-
cals; by C. Friedel and J. M. Crafts.*

In a previous researchf we studied the ethers of silicic acid,
and discovered a number of new bodies, whose structure leads
to the conclusion that the atomic weight of silicon is 28, and that
the formula of silicic acid is SiO,. Gaudin, and afterwards
Odling, first gave silicon its true atomic weight, and silicic acid
its rational formula, in order to bring them into accordance with
the well known law establishing the most simple relation be-
tween the vapor density of bodies and their atomic weight, and
their views have been adopted by many chemists ; but nitherto
conclusive proofs, based upon chemical grounds, have been
wanting to establish completely the correctness of their theory,
and a large number of the best authorities in chemistry have
adhered to the old formula, SiO 3(0=8) for silicic acid.

Our research was at first undertaken with a view to proving
that the chemical properties of silicates can only be explained
by adopting the new formula, and we have succeeded in obtain-

*The cbemical symboLi used have the values which belong to them in the new
f This Journal, II, xliii, pp. 153 and 331 ; Ann. de Ohim. et Phjs., IV, iz, p. 6.

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808 Friedel and Orafts on the ccmibinations of

ing bodies, whose existence and mode of formation it is impos-
sible to account for by any other theory. Such are the chlor-
hydrids and acetins derived from normal silicic ether, Si(C>H50)i
and at first we only studied the compounds which belong to the
same type as the normal silicic ether, but the research led us
further than we anticipated, and resulted in the discovery of
the more complicated oisilicic ethers, already described, whose
structure throws some light on the rational formulas of mineral
silicates, and also of a remarkable class of bodies, in which the
alcoholic radicals, ethyl, C^H^, and methyl, CH3, are combined
directly with the silicon, and not, as in the ethers, through the
medium of oxygen. The present paper is devoted to the de-
scription of these latter bodiea

The study of the compounds of silicon with alcoholic radi-
cals fortifies the conclusions already arrived at ; it demonstrates
the tetratomicity of silicon, and places it in the same group
with tin, titanium and carbon ; and it leads, besides, to the dis-
covery of a property of sUicon, which allies that element with
carbon fer more closely than the equality of their atomicity and
the similarities hitherto observed in the structure of their com-
pounds. In jEact, silicon has been found to possess the property
of combining directly with carbon, or rather with hydrocarbons ;
and the resulting compounds are in every respect similar to sim-
ple hydrocarbons, susceptible like them of substitution of chlo-
rine and bromine for hydrogen, and of acting as radicals in alco-
hols and ethers ; consequently silicon may take the place of car-
bon in a hydrocarbon, and in the series of bodies which can be
derived from a hydrocarbon, without modifying essentially its

It is easy to appreciate the importance of this result Car-
bon is characterized by the property of combining with itself
to build up groups of atoms, which have been compared to
chains, or nuclei, about which the atoms of hydrogen, oxygen,
nitrogen, &a, found in organic bodies, group themselves, and it
is especially this property of carbon which fits it to play the
part of the element essential to the structure of organic com-

It has been supposed that carbon alone had the property of
combining with itself to form the nuclei of organic compounds,
but it now appears that silicon shares with it this quahty, and
we are led to the opinion, that no element is unique in its prop-
erties, but that eacn has its near relatives among the others, as
was indicated by Dumas in dividing the elements into natural
families, and as every new discovery daUy tends to prove. It
is remarkable, also, that analogies 01 this Kind, whicn are inde-
pendent in their nature of the atomicities of the elements, should
occur especially between elements having the same atomicity,

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Silicon with Alcoholic Radicala. 809

and the &ct enliances the value of a classification of the ele-
ments, which is founded upon the consideration of their atom-

Silicic Ethyd.

We have obtained silicic ethyd by the reaction which is often
employed to effect the union of ethyl with metals or with non-
metalic elements^ Chlorid of silicon and zinc-ethyd do not
act upon each other at the ordinary temperature, but when
they are mixed in the proportion requisite to afford an equiv-
alent of zinc for each atom of chlorine, and heated in seal-
ed tubes to 140® centigrade, a reaction commences, and at
160° it is completed in 8 hours. On opening the tubes, a con-
siderable quantity of a gaseous hydrocarbon escapes, which,
when lighted, bums with a luminous flame. The tubes contain
a liquid, together with a solid deposit of chlorid of zinc, mixed
with gray particles of metallic zmc. The presence of metallic
zinc accounts for the production of gaseous nj^drocarbona

The liquid can be separated by distillation into several prod-
ucts. It commences to boU at 40®, and at that temperature
chlorid of silicon distils, mixed with a very volatile hydrocar-
bon, burning with a luminous flame, which cannot be condensed
alone at 0®, but which is held in solution, to a considerable ex-
tent, by the chlorid of silicon. When the temperature reaches
60®, nearly pure chlorid of silicon distils, and it then rises rap-
idly to 150®, and the greater part of the Hquid distils at 160®
to 155®.

The portion which distils at 60® to 150®, treated with water,
gives the products of decomposition of the chlorid of silicon,
together with a certain quantity of a liquid, identical in its
properties with that which distils at 150 to 155°^ in the first
operation. The portion thus obtained in both operations, dis-
tilling at 150® to 155®, washed with water and with a solution
of caustic potash, to free it from the small quantities of chlorid
of silicon which can not be easily separated oy distillation, and
then dried over solid caustic potash, distils at 152® to 154®. The
body thus obtained is not spontaneously inflammable, like many
of tne compounds of organic radicals with metals, but when
ignited it bums in the air with a luminous flame, and gives off
a white smoke of silicic acid. It is lighter than water, and is
not attacked by caustic potash nor by ordinary nitric acid. It
is also not attacked by sulphuric acid, and is insoluble in it ;
concentrated sulphuric acid, however, separates from it a smiJl
quantity of a Ixxly which will be described later. It can be
completely purified by shaking it several times with concen-
trated sulphuric acid, and decanting by means of a pipette;
finally by washing with water and by drying over meltea chlo-

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310 Friedel and Orafis on the combinations of

rid of calcium. The product, which was finally obtained by
operating in this way on considerable quantities of material,
boiled at 152°.

The method of purification with sidphuric acid was not at
first adopted, and the analyses made of tne substance boiling at
about 152°, after it had been simply treated with water and with
caustic potash, in order to remove traces of chlorid of silicon,
gave a slight excess of carbon for the first portions which dis-
tilled ; see analysis I. This was undoubtedly due to a minute
auantity of a hydrocarbon, probably ethylene, dissolved in the

The analyses of the portions which distilled last showed on the
other hand a deficiency of carbon, arising fix)m the presence of
a body containing oxygen, which can be separated by means of
concentrated sulphuric acid ; see analyses 11 and lEL We no-
ticed, also, that the liauid was at first capable of absorbing a
very small quantity of bromine, without being colored by it
After the treatment with sulphuric acid, the boilmg point oi the
liquid was almost constant, and the smallest trace of bromine
imparted its color to it, showing that no combinations took

Analysis of the liquids^ which had not been treated vnih sulphuric add,

L £WZ%^n^=151°-151i°.

Substance taken = 1868 grammes ; 00^ = '4520 grammes;

H^ 0=0-2280 grms.
IL Boiling point=lbl{''-lby.

Substance takm^0'17^ grms. ; CO^ =04127 gnns. ; H^ 0=

0-2170 grms.
m Sam£ product redistilled. Boiling point=151i°-152i°.

Substance toAen=0-1943 grms. ; CO^ =0-4685 grms.; 5,0=

0-2890 grms.

I. n. m. Oaknilated for Si(C,H.)«

0=6718 65-98 6577 66-67

H=18-60 18-88 18-67 18-89

Analyses of silicic ethyd purified by a treatment with sul-
phuric acid. Boiling point =152°-158^

L Sabstancetakm^O'ldSl grms.; CO^ = 0-4706 grow. ; 5, 0=
0-2888 grms.
IL Substance taken=0'2192 grms. ; CO ^=0'6858 grms. ; H^ 0=
0-2720 grms.
IIL Substance toie7i=0-8015 grms. ; /SO, =01250 grms.
rV. Substance toien=0-8480 grms. ; SiO^ =01895 grms.

L n. m. IV. SKCHO*.

0=66-45 66-66 6667

H=18-74 18-79 1889

Si= 19-84 18-98 19-48

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Silicon with Alcoholic Radicals. 811

The first determination of silicon was made by heating the
substance in a sealed tube with nitric acid for several hours, at
180^-190**, dissolving the contents of the tube in caustic potash,
and estimating the silicic acid in the solution in the ordinary
way. In the second determination, dilute chlorhydric acid and
chlorate of potassium were substituted for the nitric acid, and
the operation was carried on in a sealed tube as before. It is
somewhat difficult to dissolve all the silicic acid which adheres
to the tube by caustic potash.

The vapor-density of silicic ethyd was deduced from the fol-
lowing data :

Difference of weights of the bulb - - =0*5248 grms.

Temperature of the balance, - - 14**

Tempera^re of the oil-bath, - - 2]4***2

Barometer, 761*4 mm,

Oapacity of the btdb, .... 211*000.

Air remaining in the bulb, - - 1*3 cc,


Calculated vapor-density, 4*986.

The results thus obtained show that silicic ethyd corresponds
to the chlorid of silicon, and that the reaction by which it is
formed may be expressed by the equation :

SiCl,+2Zn(C,HJ,= Si(C,Hj,H- 2ZnCl,.

Silicic ethyd is a liquid resembling bodies of the petroleum
class in its aspect It has an odor like the pure hydrocarbons
of this series, and cannot be easily distinguished from them,
except that instead of burning with a carbon-smoke, it gives a
white smoke of silicic acid.

The density of the liquid at 22^*7 compared with that of
water at the same temperature, is 0*7657.

In order to obtain considerable quantities of silicic ethyd, we
used Frankland's copper digester instead of glass tubes, which
add to the inconvemence resulting from their smaU capacity,
that of being liable to explode from the pressure of the gases
formed as secondary products of the reaction.

In the digester, 100 grma of zinc-ethyd were operated upon
at once, and an excess of chlorid of silicon was always added
The first portions, which distilled below 140®, were a mixture of
chlorid of silicon with silicic ethyd, and they were always treated
over again with a fi-esh quantity of zinc-ethyd in the next ope-

We usually heated the digester in an oil-bath, at 180'*-200*\
using a gas-regulator of similar construction to Bunsen's, ana
kept each charge at that temperature^ for about ten hours. After
opening the digester and distilling up to 140®, water was added

Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 36 of 109)