The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1866-06-26
NOTES ON SCIENCE.
A NEW HYDRAUI1o CEMENr.


a few months 1t became transparent like ala
baster, and so hard as to scratch marble; ex-
amined again recently, it was ound to be In no
way deteriorated. An analysis showed it to be
nearly pure hYdrate OF magnesia, similar to the
mineral bOnoite. Deyille then stirred up pure
caustlc magnesia into dough, with water, and
sealed ii in glass tube. In q few weeks this
also became transparent, and proved upon
analysis to be pure hydrate, containing 69'3
per cent magnesla and 3O7 per cent water.
Deville further discovered that mixture of
. magnesia and gypsum did not harden under
water, but that magnesla and pulverized chalk
+ or marble, when exposed for some time to the
E action of water, forms very hard stone, SINH
lar to artificial marble. The magnesa which
. yielded the hardest mass was that prepared by
heating the chloride of magnesia obtained from
the bittern of salt water. The heat must not be
raised TO redness as the hydraulic properties of
. the magnesia are diminished By too high tenn
perature An important result was obtained
5 from do olomite, double carbonate Of lime and
= magnesia, which, heated to below redness, pull
f verized and mixed with water, yields under
4 water mass of extraordinary hardness.
If dolomite be heated to whiteness, so as to
expel all the carbonic acid it will no longer set
under water. The lime OF the mineral must
retain its carbonic acid while the heat is raised
s sufficiently TO eXpel the carbonic acid from the
magnesa. The result is an intimate mixture of
caustic magnesia and carbonate of lime (mar-
ble), which yields cement that nardens equally
4 well under fresh aud salt water, and appears to
be admirably adapted for the manufacture of
{ artificial buildng-stones. Extensive expert
ments are now being carried on with 1t in
& France, the results of which we shall present to
n our readers.
vANADIUM
Vanadium has been found in large quantities
= in the iron made from the oolitic ores oil West
81 bury, Wiltshire. In order to obtain the metal
8 the iron is nearly dissolved in dilute hydro
4 chlortc acid; concentrated hydrochloric acid is
= then added, the solution is boiled, filtered, tue
residue treated on the filter with ca lstic potash,
then with hydrOchoric add, dried and heated
in mutfle furnace. The halttused mass can
II be used in the preparation OF vanadic acid.
Il This rare metal can now be Obtained in large
quantities.
THALLIUM.
Thallium occurs, according to Bunsan, in the
zinc vltriol lye OF JulIushutte, Hartz Mountains,
10 the amount of 0'05 per cent, and can, there
fore, be easily prepared by the pound. Very
i frequently, in the manufacture of suphate of
zinc, and in the residues from galvanic bat
terles, thaillnm Is also contained. 1t can be eX-
tIacted as folio ws:-Copper, cadmium, and thai
lium are thrown down by means OF Zlnc-foil,
washed in a bag, and then digested in water
containing little sulphuric acid. The solution
from this contains camdIum and thalllum. The
latter can be separated as iodide OF thallium by
means OF the iodIde OF potassium.
II Scott has found in the sand OF Alum Bay, Isle
of Wight, large quantities of thallium. The
# metal has also been found in the sugar-beet,
grape luce, chlckory root, in tobacco and kelp.
LITHIUM.
A mineral spring has been discovered in Red
ruth, Cornwall, very rich in lIthIa. According
hours eight hundred pounds OF chloride OF
lithlum, and one gallon OF the water contains
26'05 OF the chlorde.
TELLURIUM.
This exceedingly rare metal has been found to
the extent of five per cent. in the Oismuth ore of
Mount lllampu, BOLIVIA, fifteen thousand feet
above the level of the sea. As this ore is ex-
tensively worked there is a prospect OF a larger
supply OF tellurium than has hitherto been
known.
BENzo1c ACID.
This acid a few years ago had simply scien.
titic interest, and was occasionally applied in
III medicine. The high pric e OF the acid pTeparet
II from gum benzoin prevented its application in
H the arts. Recently Its preparation from hppu-
rc acid has opened way tor its extensive
< manufacture. 1t is now manufactured near
Nuremberg, and employed in the treatment of
tobacco, as mordant in calico printing, and
IN especially in the production of analine colors.
~ BenZoic acid is also procured on a large scale
from naphthaline, hitherto worthless product
# of the gas manufacture. BY these two methods
the acid can be obtained in any quantity, and
# further applications and uses oil 1t VIII no doubt
& be discovered.
III sELF-REGULATING AND ALARM THERMOMETER.
In order to control the temperature of hot
houses, NORM has constructed a thermometer
as tollows:-A platinum wireI is fused into the
bulb and a second wire is inserted at the 10 west
- degree Whcn can be tolerated in the building.
Both wires are connected with a galvanic bat.
tery. AZ long as the mercury stands at the
proper height, thus indicating sufficient heat,
the current Is CLOSED; anu d mdSnelO-eleCIrlCdl
apparatus, in the dwelling OF the keeper, is
kept in motion; but il the building becomes
cold the mercury sinks, the current is broken,
and the magnetic apparatus ceases to move.
DR.. Kohlrausch has modified this apparatus SO
as ito be self-regulating. By similar contri
II vance he opens and shuts the yentilators accord
n ing to the temperature-the whole system being
- driven by an electro-magnet.
II WASH FOR HARDENING PLASTER CASTS.
Knaur and Knop, OF Lepsic, have published
81 after long years OF experiment, method Tor the
II hardening of plaster casts that they can be
i washed and better preserved. The process con
sists in he application OF a mixture oil soluble
"A glass With an albuminous substance, which lat
ter forms a cement with lime and haTdens WheI
Z mixed with soluble glass.
4, The stock bottles are prepared as folows:-
#l No. !. SyTopy soluble glass. No.. 2. solution
f of one part OF caUstlc potash in i've parts OF
VI water, which n ust be kept closely stoppered
No. g. Sour milk, which is obtained by setting
i pan of milk to sour and removing the curd
No. A. A clear solution OF lime water.
Il To apply the wash, shake up the milk anC
pour out as much as may be desired into a suit
N able vessel. Add the potash oy drops nom No
IA until the casein precipitated remains dissolved
8 and the liquid is simply cloudy, but not colored
Ht Add to this one-iourth its volume OF soiubl
& 4 glass. The mixture must be prepared whel
wanted as it will not keep. 1t can be applied
" with IA clean paintbrush, and several coats cal
TN be given if required, alter the first is entirel
dry. Black spots on the casIs, produced by tn
non OF the plaster, generally disappear whe
II the whole is dry. If the above mixture is no
H well applied, or if it does not harden, 1t can
washed off with sponge by using the lime
water from No. A, and the operation can
repeated.
n the entire mass, by the addition of some sul
. stance 10 the water III which the plaster wa
. llu eli nTOVpn nnRlcppgSlnl.