718 PHILOSOPHICAL TRANSACTIONS. [ANNOI79O. 



air; whereas the soluble part resembles the fluid which is extricated from 

 cancerous matter by the vitriolic acid : it has a fetid odour, it decomposes 

 nitrated silver, combines with caustic volatile alkali, and possesses many of the 

 properties of common hepatic air. 



There are several particulars however, in which the animal and common 

 hepatic air materially diflcr from each other. Though they are both fetid, yet 

 their odours are not exactly similar. When common hepatic air is decomposed 

 by the concentrated nitrous or dephlogisticated marine acid, sulphur is separated; 

 but when animal hepatic air is decomposed by these acids, a white flaky matter 

 is disengaged which is evidently an animal substance, because it becomes black 

 by the addition of concentrated vitriolic acid. Sulphur is also separated during 

 the combustion of common hepatic with atmospherical air; but when the air 

 from animal substances is burned with atmospherical air, no precipitation of 

 sulphur takes place. Indeed, that animal hepatic air does not contain sulphur 

 will be apparent from the following experiment. Equal parts of pure air and of 

 air extricated from fresh beef by distillation, were fired by the electric shock in 

 a strong glass tube over mercury. A little distilled water was then introduced 

 through the mercury into the tube, and was agitated with the air which it con- 

 tained. A portion of this water being filtered, and a small quantity of muriated 

 barytes being dropped into it, the mixture remained perfectly transparent. Hence 

 it appears, that the air extricated from fresh beef by distillation does not contain 

 sulphur ; for, if it had contained that substance, the sulphur, by its combustion 

 with the pure air, would have been changed into the vitriolic acid, and the mu- 

 riated barytes would have been decomposed. 



The following experiments were made with a view more accurately to analyze 

 the airs which are disengaged from animal substances by heat, and to determine 

 the products resulting from the union of these fluids with pure air. About an 

 ounce of the lean of fresh mutton was introduced into a small coated glass retort, 

 and exposed to a red heat. The air extricated towards the end of the distillation 

 was received over mercury ; and soon after its production, being agitated with 

 water, very nearly -i of it was absorbed. A similar experiment being made with 

 the air disengaged towards the middle of the distillation, the part of it which 

 was soluble in water was found to be to the part not soluble in that fluid, as 2 

 to 3. Having suffered a separate portion of the air disengaged towards the end 

 of the distillation to remain over mercury for 7 hours, it was found gradually 

 to diminish in bulk, and a fluid, which had the colour and the odour of a thin 

 empyreumatic oil, was collected at the bottom of the jar. The air being now 

 agitated with water, only -f of it was absorbed. Hence it appears, that a portion 

 of the air, extricated from animal substances by heat, resembles a species of 

 hepatic air which was first discovered by Mr. Kirwan, and which exists in an in- 



