M. Favre on Thermal Action in Chemical Processes. 227 



fore coagulation has set in. To prevent the latter without decom- 

 posing hienioglobine, &c, Masia* found it advantageous to mix 1 

 part of blood with 2 parts of a 4 per cent, solution of crystal- 

 lized phosphate of soda. In twenty -four to forty-eight hours 

 the clear layer acquires a height of 2 centims., and may be 

 easily removed. Neither in it nor among the precipitated blood- 

 corpuscles is any coagulation perceptible. 



Favre f has made the following observations on thermal 

 actions in chemical processes. For the purposes of the investi- 

 gation he used the heat of a voltaic battery. Of two mercury 

 thermometers, one very accurately measures the internal heat of 

 a battery of five equal zinc-platinum elements. In the other, 

 there are inserted, in a series, a zinc-platinum element of ex- 

 actly the same dimensions as those in the other calorimeter, 

 then a voltameter consisting of platinum foils of the same size 

 as the zinc-platinum strips, and finally a voltameter with 

 two exactly similar copper strips. The latter are immersed 

 in a solution of sulphate of copper. Comparing the disengage- 

 ment of heat observed in these various experiments, it is found 

 that the battery yields the quantity of heat necessary for the 

 decomposition of the bodies, and the separation of their con- 

 stituents. This quantity of heat is greater than that which the 

 same materials disengage in their combination. Hence at the 

 moment of formation (status nascens) bodies possess an excess 

 of heat, which they part with on entering into the ordinary con- 

 dition in which we know them. We must assume, therefore, 

 that the molecules concerned in chemical reactions, before enter- 

 ing into combination, or being given off in decomposition, un- 

 dergo a change. Disengagements or absorptions of heat occur, 

 which are quite independent of the thermal phenomena which 

 accompany every chemical combination or decomposition. If 

 the affinity is to be measured by the quantity of heat which the 

 molecules exhibit in reactions, a conclusion can never be drawn 

 as to the magnitude of the affinity from the permanence of com- 

 pounds; for compounds whose constituents absorb in their se- 

 paration the same amount of heat, will decompose more readily 

 the more readily these constituents, once separated in the nas- 

 cent state, disengage heat in their passage into the ordinary 

 condition. 



Preyer has described! a new analytical method for distinguish- 

 ing colouring-matters, based on the phenomena which they pre- 



* Arch, fur path. Anat. vol. xxxiv. p 436. 



t Comptes Rendus, vol. lxiii. p. 369. 



X Sclmlze' sArchiv fur mikro. Anat. 1866. 



