262 ESSAY XXIV. 



hot temperature as in the cold; and should there be any 

 superfluous vitriolic acid, it will be found in the residuum. 

 This crystallised acid of lemons cannot be changed by the 

 action of nitrous acid into acid of sugar ; but the saponaceous 

 extract may be totally converted into that acid. 



DISCOVERY OF A PECULIAR SWEET AND VOLATILE 

 MATTER, WHICH IS A CONSTITUENT PART OF EX- 

 PRESSED OILS AND THE FAT OF ANIMALS. 1 



Several years ago, upon dissolving litharge in olive oil, 

 I observed a peculiar sweet matter, distinct from the oil, 

 floating on the surface, which, when inspissated and treated 

 with nitrous acid, appeared to be a modification of the acid 

 of sugar. I have since more particularly examined this 

 peculiar phenomenon, and have discovered the sweet matter 

 as well in linseed oil, oil of almonds, and of rape-seed, as in 

 oil of olives ; and, still more lately, both in hog's grease and 

 butter. In my experiments, I made use of the following 

 process : One part of pulverised litharge was dissolved in 

 two parts of some one or other of the unctuous substances 

 above mentioned and some water, the mixture being made 

 to boil all the time. As soon as it was inspissated to the 

 thickness of salve, the whole was left to cool, and then the 

 water was poured off. The water is found to contain the 

 sweet matter in question ; and it is to be evaporated to the 

 consistence of syrup. If the oil or fat be fresh, there does 

 not appear any sign of dissolved calx of lead, on addition of 

 the vitriolic acid ; but should either the one or the other be 

 old and rancid, some calx will then be dissolved, and should 

 be precipitated by a proper quantity of vitriolic acid. If 



1 This is taken from tlie second part of Crell's Chemische Annl< //, 

 p. 99. 



