168 Prof. Thomson on the Dynamical Theory of Heat. 



7-34 grains substance gave 5-5 4 carbonic acid and 0-56 water. 

 4-68 grains substance gave 3-29 sulphate of lead. 



Calculation. 



Experiment. ( ^ ^ 



Carbon . . . 20-57 19-91 Ci» 60 



Hydrogen . . 0085 00-99 H^ 3 



Oxygen 16-19 0« 48 



Bromine 26-01 Br 78-26 



Oxide of lead . 36-48 36-90 PbO 111-56 



100-00 10000 300-82 



The composition of this salt is therefore expressed by the for- 

 mula PbO, CIO H2 B,, 05 + HO. 



I have also obtained a su.bstitution product of iodine, by ope- 

 rating in a particular manner, which I shall describe in detail in 

 a future paper. I shall conclude this communication with a list 

 of the substances described in it along with their formulfe. 



These experiments were performed in the laboratory of Dr. 

 Anderson, to whom I am mxich indebted for assistance. 



Pyromeconic acid . . . 010 113 0^ + HO. 



Pyromeconate of baryta . - BaO, C^^ H^ 0^ + HO. 



Pyromeconate of strontia . SrO, C'o H^ 0^ + HO. 



Pyromeconate of lime . . CaO, CioR^O^ + HO. 



Pyromeconate of magnesia MgO, C'° H'^ O^. 



Pyromeconate of lead . . PbO,Ci0H3O5. 



PjTomeconate of copper . CuO, C^^ H^ 0^. 



Pyromeconate of iron . . Fe^ 0^, 301° H^ 0^. 

 Bromo-pyromeconic acid . C'o H^ Br 0^ + HO. 



Lead salt PbO, C'^H^Br O^-f-HO. - 



Edinburgh, July 1, 1852. 



XXV. On the Dynamical Theory of Heat, with numerical results 

 deduced from Mr. Joule's equivalent of a Thermal Unit, and 

 M. Regnault's Observations on Steam. By William Thomson, 

 M.A., Fellow of St. Peter's College, Cambridge, and Professor 

 of Natural Philosophy in the University of Glasgow. 



[Concluded from p. 117.] 



Part III. — Applications of the Dynamical Theory to establish 



Relations between the Physical Properties of all Substances. 

 44. rr^HE two fundamental equations of the dynamical theory 

 -I- of heat, investigated above, express relations between 

 quantities of heat required to produce changes of volume and tem- 

 perature in any material medium whatever, subjected to a uniform 

 pressure in all directions, which lead to various remarkable conclu- 



