Chemistry and Physics. 115 pe 
pump experiment, in which the equilibrium between a solid ball and 
hollow bulb is disturbed when placed under an exhausted receiver. 
n the practical construction of the instrument a closed glass bulb 
is suspended from a hook carrying an agate plane, which rests on a 
knife edge at the short arm of a beam, the fulcrum of which is pro- 
vided with a knife edge, &c., as in an ordinary balance, while the long 
arm terminates in a vernier, the angular deviation being measured on a 
graduated arc—forming in fact a species of bent-lever balance, the 
arms however being nearly in a line. 
The instrument can be so adjusted as to become more delicate than 
a barometer reading to ‘001 of an inch, A series of observations are 
given compared with the density as calculated from an aneroid barom- na 
‘he 
eter. The changes indicated by the two instruments are the same in 
direction but not proportional. G. C. 8. 
1 reservation of the Proto-Sulphate of Iron from Oxydation ; 
by M. Ruspint, (Journ. de Chim. Med., vol. v.)—The crystals are to 
be dried in blotting paper, and allowed to effloresce in a drying appa- 
ratus at 86° he salt may then be kept unchanged in bottles with 
glass stoppers, 
e have seen the same result attained more readily by precipitation — 
3. C. 8 
with alcohol. G 
17. Freezing point of Water lowered by Pressure; by Prof. W. 
Tuomson, (L., E. and D. Phil. Mag., Aug., 1850.)—Mr. James Thom- 
son the brother of the author has recently shown that the fundamental 
axiom of Carnot’s theory of the motive power of heat, requires as a ne- 
cessary consequence that the freezing point of water should be lowered 
by pressure. The result of his calculations gi 0135 ofa degree of Fah. 
as the depression in temperature for each atmosphere 29-922 inches. 
f 
tions. A suitable thermometer containing ether instead of mercury 
was inclosed in a glass case and hermetically sealed. Each division 
of the scale was equal to about y of a degree. The experiments 
re in Oersted’s apparatus for the compression of water—the cylin- 
der being filled with ice and water. The column of ether was found 
to descend immediately upon the application of pressure, and to rise 
as rapidly when the pressure was withdrawn. 9 
Observation at Siacacuesbies gave a depression of 0-106" F.—at 
m, 0°232° F., differing by —0:003° F. and 0-005 F. from the 
oincidence with theory. » Go Be 
. Test for the Presence of Chloroform in the Human body; by 
et in Gaz., June, 1850. )—— e blood or 
her paris examined are heated by a chlorid of calcium , 
oe 
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