Development of systems for storage of thermal energy is discussed. Application of phosphonium chloride for heat storage through reversible dissociation is described. Chemical, physical, and thermodynamic properties of phosphonium chloride are analyzed and dangers in using phosphonium chloride are explained

Heimlich, P. F.

Sutton, J. G.

Tepper, E. H.

English

NASA Technical Reports Server

August 1972	 B72-10422 
NASA TECH BRIEF 
Ames Research Center 	 4V 
NASA Tech Briefs announce now technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Phosphonium Chloride for Thermal Storage 
Many systems used in space as well as on earth 
involve the storage of heat. For example, solar heat-
ing systems depend heavily upofi the efficient storage 
of the heat collected when the sun shines and the 
restitution of stored heat at night or over those inter-
vals when solar radiation is obscured. 
Materials containing water, of crystallization, or 
materials which have high heats of fusion or undergo 
reversible dissociation near room temperature, are 
found to be most efficient for storage of heat; cheap 
materials which have high densities and heat capaci-
ties are especially attractive. 
The results of an extensive survey have indicated 
that scarcely any substance with a melting point 
between 50° and 150°F (10° and 66°C) has a heat of 
fusion greater than that of water. However, it has 
been found that phosphonium chloride, PH4C1, has a 
heat of fusion several times larger than that of water 
and thus it is appropriate to consider it a candidate 
material for thermal storage systems; a number of 
designs which take advantage of the thermal proper-
ties of phosphonium chloride have been studied. The 
following table contrasts some of the pertinent prop-
erties of phosphoniurn chloride and water. 
Phosphonium chloride is formed at low tempera-
ture by combining equimolar quantities of phosphine 
(PH3) and hydrogen chloride (HC1). Solid phosphon-
ium chloride sublimes at pressures below 500 psia 
(3.5 MN/m2 ) at room temperature; if the pressure is 
decreased, the substance dissociates into phosphine
and hydrogen chloride. Systems employing the com-
pound must be carefully designed to minimize the 
probability of failures which may lead to release of 
highly toxic phosphine. 
Property Water PH4C1 
Melting point, °C 0 28 
Triple point 0.01°C, 28°C, 48 atm 
4.5 mm Hg (100 kN/m2) 
(599 N/rn2) 
Specific gravity 1 1.7-2.0 (est.) 
Heat of fusion, cal/g 80 180 
Hazards none toxicity 
Dissoc. pressure none 1 atm (10 N/rn2) 
below 0°C
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP 72-10422 
Patent status: 
No patent action is contemplated by NASA. 
Source: James C. Sutton, Philip F. Heimlich, 
and Edward H. Tepper of 
United Aircraft/Hamilton Standard Division 
under contract to 
Ames Research Center 
(ARC-10572) 
Category 04 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights. 
https://ntrs.nasa.gov/search.jsp?R=19720000421 2020-03-17T03:38:40+00:00Z


Phosphonium chloride for thermal storage

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