24 Memoir upon Cnffes. 



impossible, on account of its small quantity, foiletermine 



the nature of this residue, which was black Inclining to 



gray. 



The liquid product contained in the receiver contained 

 in all 0-45 of the mass distilled ; whence I concluded that 

 the amount of the gas formed during the operation was 

 nearly 0-19. The empyrcumatic oil separated from the 

 aqueous liquid, and a little soapy, weighed 0-1.5 ; the water 

 0-30. 



The acid of coffee which' I obtained pure was dissolved 

 in six limes its weight of pure water; in this state it 

 was mixed with the following substances : with turnsole 

 and violet tinctures, which it reddened very suddenly ; with 

 solutions of oxygenated and green sulphate of iron, the 

 former solution immediately assumed a fine green colour, 

 and after resting six hours there was a precipitate formed of 

 the same colour; the latter solution at first only assumed an 

 extremely slight green tint, but this became deeper upon 

 being exposed some hours to the air. Gelatine was not pre- 

 cipitated by the acid of coffee; the muriates of tin and 

 lead were precipitated very suddenly and very abundantly 

 in grayish white ; muriate of antimony, in a flaky white, 

 verv suddenly ; the nitrates of mercury and bismuth in dirty 

 white ; the nitrate and acctite of copper in a sombre brown; 

 the nitrates of silver and cobalt, the sulphates of manganese; 

 zinc, and copper, underwent no alteration ; that of copper 

 only lost in colour; the nitro-muriates of gold and platina 

 lost nothing, not even their colour. 



The action of the sulphuric, sulphurous, nitric, nitrous, 

 muriatic, oxymuriatic, and phosphoric acids only gave this 

 vegetable acid a yellow tint more or less beautiful in the 

 co'ld; by heating theni mixed, the sulphuric acid became 

 highly coloured, and liberated vapours of sulphurous acid; 

 the nitric acid was easily decomposed with a disengagement 

 of gaseous oxide of azote and carbonic acid, which preci- 

 pitated lime water. The residue of this kind of combustion, 

 Bubjectcd to some trials, seemed to me to be only malic acid, 

 npt precipitating lime from its combinations like the oxalic. 

 The o;<yuu;ri."tic acit! gave a similar product. 



Among 



