Calvert-type, twin liquid metal solution calorimeter determines the heats of formation of transition metal alloys at high temperatures. The twin differential calorimeter measures the small heat effects generated over extended periods of time, has maximum operating temperature of 1073 degrees K and an automatic data recording system

Darby, J. B., Jr.

Kleb, R.

Kleppa, O. J.

English

NASA Technical Reports Server

Specimen 
Storage
Reciprocating Head 
Thermopile 
Calorimetric Cell 
Silver Block 
Movable Ph 
Outer Stainless
Steel Tube 
Furnace Core 
Inner StainlE 
Steel Tu 
	
April 1968
	 Brief 68-10083 
S	 C. AEC-NASA TECH BRIEF 
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application. Tech Briefs are published by NASA and may be purchased, at 15 cents each, from 
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Twin Solution Calorimeter Determines Heats 
of Formation of Alloys at High Temperatures 
The problem: 
To develop a calorimeter capable of determining 
the, heats of formation of transition metal alloys at 
high temperatures. Calorimeters with single reaction 
cells have proved very successful in determining heats 
of formation of alloys when the reaction period is 
short and when moderate heat effects are observed. 
Errors increase substantially, however, when the 
metals or alloys dissolve slowly in a chosen solvent:
the transition metals dissolve very slowl y at tempera-
tures suitable for precision calorimetry. 
The solution: 
A Calvet-type, high temperature, twin liquid metal 
solution calorimeter, particularly suited for determin-
ing the heats of formation of alloys containing transi-
tion elements. This twin differential calorimeter 
precisely measures the small heat effects generated 
over extended periods of time. It has a maximum 
(continued oc rican 
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operating temperature of 1073 1 K, and is equipped 
with an automatic data recording system. The 
performance of the calorimeter has been checked by 
measuring the heats of solution of pure noble metals 
in tin at 685°K. The results agree with existing 
published data. 
How it's done: 
The twin solution calorimeter consists basically of 
two calorimetric cells contained within two symmetri-
cally located cavities in a single metal block thermo-
stat, two thermopiles, a resistance furnace, a recipro-
cating head to which stirrers are attached, a specimen 
storage and dispensing device, a movable platform, 
and inner and outer stainless steel tubes. 
The thermostat consists of a cylinder of pure silver 
25.4 cm in diameter and 25.4 cm high. Silver is used 
because of its high thermal conductivity and resistance 
to atmospheric corrosion. Two cylindrical wells 10 cm 
in diameter are located symmetrically in the silver 
block and are covered by removable 2.5 cm thick 
silver lids. A calorimetric cell is located in each of 
the enclosed wells. The cell consists of a silver tube 
which is precisely fitted over the closed end of a 
stainless steel tube. The latter passes through the top 
lid of the block, to which it is securely fastened in 
good thermal contact, and extends to the top of the 
water-cooled vacuum chamber. This stainless steel 
tube provides: (1) a means of suspending the calori-
metric cell within the cavity of the block, (2) a gas-
tight environment for the interior of the calorimetric 
cell, and (3) an access to the interior of the cell with-
out disassembling the apparatus. 
Two thermopiles, which detect a temperature differ-
ential between the calorimetric cell and the cavity 
wall, are located in the annular space between the 
cells and the cavity walls. Each consists of 176 
junctions, which are spot welded to gold terminals. 
Half the terminals are attached to the surface of the 
cells, the other half to the inner surface of the 
surrounding silver block. The attachment of these 
junctions provides adequate heat transfer even when 
the apparatus operates under vacuum. Mica washers 
or strips, approximately 0.05 mm thick, provide 
electrical insulation. 
The two thermopiles are connected in a differential 
arrangement such that temperature drifts in the silver 
block produce emf's that exactly cancel. Thus the emf 
signal is essentially independent of temperature 
fluctuations in the block. The signal may be amplified 
and recorded as a function of time. This emf signal 
is proportional to the rate of heat transfer, and the 
total area under the emf—time curve is then a measure 
of the heat of reaction. 
The temperature of the calorimeter is measured by a 
platinum/platinum-10% rhodium thermocouple. The 
temperatures within the calorimetric cells and the 
Brief 68-10083
silver block are identical when thermal equilibrium is 
attained. 
The procedure used in determining the heats of 
solution of several pure metals in liquid tin is as 
follows: The solvent, about four moles of tin, is con-
tained in recrystallized alumina crucibles which fit 
snugly inside the removable stainless steel tubes. 
Solid specimens, of a mass to yield an intended heat 
effect of approximately 50 cal, are placed in the speci-
men storage device. The top chamber is evacuated to 
I x 10- 6 mm Hg and the inner tubes are lowered into 
the calorimeter. After the tin melts, the stirrers are 
turned on and the chamber is filled with 99.999% 
pure argon gas at a slight positive pressure with 
respect to atmospheric pressure. Thermal equilibrium 
is attained in about 18 hours, after which the tempera-
ture drift does not exceed 0.1 0 K per day. 
Each calorimetric experiment lasts approximately 
150 minutes. In this period the heat pulse in the 
calorimeter is dissipated and the emf of the differ-
ential thermopile returns to the original value. 
Notes: 
1. Additional details describing furnace, shields, tem-
perature controls, auxiliary features, instrumenta-
tion, and calibration are contained in Review of 
Scientific Instruments, vol. 37, no. 2, p. 164-167, 
February 1966. 
2. This information should be of interest to the 
metals and chemical industry, testing laboratories, 
and manufacturers of calorimeters and related de-
vices. 
3. Inquiries concerning this innovation may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B68-10083 
Source: J. B. Darby, Jr.,

Metallurgy Division

and R. Kleb,

Solid State Sciences Division
Argonne National Laboratory

and 0. J. Kleppa
University of Chicago

(ARG-l01 14) 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439
Category 01


Twin solution calorimeter determines heats of formation of alloys at high temperatures

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