with the Oxides t)f Lead and the Alkalis, 4 J 



rine by the property it possesses of dissolving the yellow- 

 oxide of lead 5 that its saccharine taste is independent of the 

 presence of the oxide ; that it differs from sugar by its vo- 

 la«Hty, and by the impossibility to ferment it. 



That oil deprived of the principles which have given rise 

 to the sweet principle, and of the quantity of hydrogen and 

 carbon which constitutes it a fixed oil, acquires several of 

 the properties of the volatile oils. 



Finally, that this last state of oil is the only one which 

 can be combined with the white oxide of lead. ' 



From the knowledge I have acquired of the theory'of this 

 combination of the oils, I did not think it right to neglect 

 to ascertain to what extent the opinion of several chemists 

 is founded, who consider the plasters as true metallic soap€. 

 The analogy between the plasters and the soaps can only h^ 

 verified by observing in their respective combinations a re- 

 semblance in the phaenomena, or at least in the results. 



I mixed some pure soap-makers' ley with olive oil ; I ex- 

 posed this mixture to the air under a bell glass. Eight days 

 afterwards there was only a slight absorption -, the soap had 

 still a strong alkaline taste, and the oil of this soap was not 

 entirely dissolved in alcohol: but at the end of six weeks 

 the absorption of the oxygen was complete; the soap was 

 very white, of a good consistenc:e ; the alkaline taste was but 

 feeble; diluted sulphuric acid liberated carbonic acid frouri 

 it ; the oil proceeding from this decomposition had the same 

 consistency with that from the plasters, was dissolved cold 

 in alcohol with the greatest facility, and was precipitated 

 from it by water. 



I made soap in the same way as the soap-makers j I exa- 

 mined with the greatest care the liquor remaining afier the 

 operation was finished, but I could discover no trace of 

 sweet principle. 



As the absence of this principle in the alkaline soap-ma- ; 

 king probably depends only upon a greater or less subtrac- ; 

 tion of carbon or hydrogen, and the action of oxygca 

 wpon oil, and the state of the oil, are ^baoluiely the same ia - 

 the making of.plafit,ers as ia soap-making, 1 thiuk the plas- 

 ters 



