1818.] their Combinations with Alkalies. 277 



atid, fusible at 123-5°. It appears then that in this process the 

 acid matter was to the matter which was not acid in the propor- 

 tion of 55-15 to 44-85. 



The changes which take place in the transparency of the fluids 

 which have been described, in a range of not more than 10°, are 

 worthy of being noticed, as it may, perhaps, enable us to explain 

 by the laws of chemical affinity some of the phenomena which 

 are observed to take place in the fluids of living animals, and 

 which have been generally supposed to be independent of che- 

 mical and physical powers. 



The existence of what was called the cetic acid was deduced 

 from the two following observations ; 1 . That the saponaceous 

 mass resulting from the action of potash on cetine, diluted in 

 water at 176°, did not permit any of the fatty matter to separate 

 at the surface, so as apparently to prove that the fatty matter 

 had been completely acidified by the action of the alkali. 

 2. That litmus was not reddened by the alcoholic solution of the 

 insoluble matter which is separated when we treat the sapona- 

 ceous mass of cetine with water, a circumstance which seemed 

 to prove the absence of the super-margarate of potash in this 

 insoluble matter. The first of these observations has been better 

 explained on a different principle ; and it now remains to show 

 why the alcoholic solution of a substance, which certainly con- 

 tains super-margarate of potash, does not affect the colour of 

 litmus. When the true nature of this substance had been disco- 

 Tered, it was at first supposed, that the fatty substance which 

 was not acid might be alkaline, and that it might neutralize the 

 excess of acid in the super-margarate of potash. This opinion, 

 however, M. Chevreul afterwards abandoned, and was induced 

 to ascribe the effects to the great concentration of the alcohol 

 which he employed. The following experiments were performed 

 in order to show that this was the true explanation of the facts. 

 In five parts of alcohol, of the specific gravity of *791, 0*02 of 

 the super-margarate of potash was heated ; a solution was 

 obtained which did not yield any precipitate when it was cooled 

 to 86°, and which did not redden 0-26 parts of a watery extract 

 of litmus, containing 1 1 per cent, of solid matter, when added 

 to it drop by drop, and even when heated to the boiling point. 

 If five parts of water be afterwards poured into the solution, no 

 precipitate is produced, but the litmus acquires the red colour. 

 To render the experiment more striking, we may tinge the water 

 blue with litmus, to show that the effect cannot depend upon any 

 acid contained in the water ; if we then add 10 parts of water to 

 the red fluid, the super-margarate of potash will be precipitated, 

 and the litmus will resume the blue colour. The fact may be 

 explained upon the principle, that the excess of margaric acid 

 in the super-margarate of potash, when dissolved in alcohol of 

 the specific gravity of -791, is more strongly attracted by the 

 neutral margnrate of potash than it is by the potash of the litmus, 



