General Catalogue Chemistry - BECO Internacional LTDA.

analysis methods
667 325
Calorimeter for solids and liquids
Used to measure the enthalpy of reaction when
burning solid or liquid substances. The unit is
made principally of glass. The lower section of
the calorimeter is equipped with a glass inlet
nipple for continuous supply of oxygen, the holder
for the porcelain crucible with the product
being oxidized, and the electrical lead for the
incandescent wire coil required for ignition. The
course of the reaction can be observed from
the outside through the glass section, thus
allowing for continuous control. The hot combustion
gases are cooled in the double-helical
heat exchanger, warming the calorimeter liquid
(e.g. water) by several degrees Kelvin. The
double-helical design of the heat exchanger
minimizes the amount of heat lost in the form of
residual heat in the combustion gases.
This calorimeter is suitable not only for determining
the molar combustion enthalpy of chemically
defined compounds; it is just as good for
measuring the calorific value of foods. There
are two incandescent coils of differing diameters
available, the choice depending on the
ignition temperature and incineration period for
the material being tested.
Replacement to calorimeter 667 325:
667 324 ignition coils , set of 2
Measuring the combustion enthalpy of
carbon
sulfur
sugar
fats (e.g. vegetable oils)
bread
667 326
70 LEYBOLD DIDACTIC · GENERAL CATALOGUE CHEMISTRY
Calorimeter for gases
Used to determine the enthalpy of reaction for
gaseous substances.
Two gases are caused to react inside this
calorimeter and the heat of reaction is measured,
e.g.
hydrogen and oxygen
hydrogen and chlorine
carbon monoxide and oxygen.
The gases are forced out of two gas syringes
and through two capillary tubes into the path of
an electric arc. Continuous combustion takes
place here.
The combustion gases and the excess of one
of the reaction gases flow through a helical
heat exchanger, where the heat of reaction is
transferred to the calorimetric fluid, and thence
into a third gas syringe (e.g. > 665 914). The
amount of fluid in the heat exchanger is kept
small since gas reactions using gas syringes
allow only small quantities of a substance to be
burned. In addition we recommend that the
calorimetric liquid used be a substance of low
heat capacity, e.g. trichloromethane. The
temperature rise is measured with a precision
thermometer (> 666 176) or temperature
sensor (> 666 193) connected to the temperature
measurement instrument > 666 190
or > 666 210. The unit is made entirely of
glass. This gives the following advantages:
All the processes are visible.
Heat losses are low, particularly as the unit is
not in any direct contact with any metal parts
(stand components).
We recommend using the spark gap power
supply > 667 820 to supply the arc. When
using other high voltage sources please bear in
mind that excess power can cause the platinum
wire to melt.
Complete with 5 GL 18 threaded connectors
used to attach three gas syringes and the
thermometer and to vent the system.
667 322
Calorimeter for measuring evaporation cooling
Every change in state of matter requires conversion
of energy. This can be measured as a
change in temperature. The effect can be
demonstrated and analysed quantitatively with
the calorimeter. Included with the unit is a
detailed description of the experiments and calculations
for the calorimetric data.
Advantages:
Clarity for students - the unit is made of glass
Resistance to chemicals
Short reaction times
Low heat losses
Determining the heat of solution
and neutralization
Determining the evaporation cooling of
media with low boiling points (e.g. alcohol,
ether, water)
Determining the heat of solution of gaseous
ammonia in water and reversal of this reaction
Demonstrating the function of a compressor
refrigerator and a heat pump