Jithcfs.—TnftamiUit'ion of Oils. ^27 



After the intumefcevice has fabfided; the pitchy matter, which is merely oil, rendered' thick 

 by charcoal, takes this lad ftatc by the concentration of the acid, and begins to feparate t«» 

 fuch a degree the that liquid becomes vifibly clearer. 



The diftillation being ftill urged, all this charcoal becomes colleiSted together; fulphureous 

 gas paff^s over, and afterwards oil of vitriol, llightly coloured by charcoal. All the acid 

 pafles at laft in this degree of concentration, and the refidue at the bottom of the retort is a 

 plate of pure charcoal; fuch as is obtained by di^lillation of fulphuric acid from any charcoal 

 .whatever. 



When, in order to obtain the olefiant gas of the Dutch chemifts, three parts of the acid 

 are dIfUllcd with one of the fpirit of wiiif, the pitchy matter bjcomes entirely charred, and in 

 this manner a dram of drv charcoal is obtained from one ounce of alcohol. 



Oil the Infiammation of Oils by the Nitric Acid. 



With ftrong nitric acid of the fpecific gravity 152 it is impoffible to inflame linfeed oil by 

 the ordinary method; but in order to fucceed in fuch a manner as to form a ftriicing appear- 

 ance, it is proper to pour linfeed oil gently to the depth of an inch upon the fame depth of 

 the acid. The wine-glafs (verre a patte) being then placed upon a plate with a fmall quan- 

 tity of water, die whole is to be covered with a bell-glafs, fufficiently tall. In lefs than 

 a quarter of an hour the ebullition begins, which is fpeedily followed by the inflammation. 

 The experiment fucceeds equally well, though rather more flowly, with acids of 149 

 and 150. 



Oil olive treated in the fame manner, but always wiih the mixture of fulphuric acid, takes 

 fire with the fame fuccefs. In thefe experiments the operator has the fatisfadiion to obfervc, 

 at his eafe, the charcoal difengage itfelf from the other principles of the oil before the 

 inflammation. 



And in order to obferve with accuracy the changes which the acid undergoes, on its part, 

 from the olive oil, for example, two fingers depth of the latter, are to be poured on the fame 

 quantity of acijl, at 149, or thereabouts, placed at the bottom of a cylinder, with a foot, of one 

 inch in diameter; and the line of contact of the two liquids being marked, the following ef- 

 feifls arc feen : 



The height of the acid is rapidly dim.iniflied ; nitrous gas efcapes through the oil ; and the 

 phenomena are completed when the remainder of tlje acid, becoming too aqueous, ceafes to 

 a6l on the oil, which on the other hand becomes fomewhat thickened. 



If, inftead of oil, a fpirit of wine of 35° (0,842. I. p. 39), all the feries of phenomena 

 which belong to the formation of nitric acid are very agreeably obferved. This procefs, in 

 fome refpefls, refembles that of Black, which confifts in fkilfully caufing three ftrata of 

 different liquors in a matrafs, placed in ice-cold water. Thefe liquors are the fuming acid, 

 waier, and fpirit of wine. Thefe three ftrata may be eafdy arranged by means of a ball and 



y u 3 fyphon, 



