Chap. 3.] Air Bladders of Fijh fitted toitb Azotic Gas. 383 

 that contains it, its weight will be found to be to tha? 

 of common air as 985 to j ooo, the barometer ftandino- 

 at 30.46, and the thermometer at 60". 



Various fubilances alfo are productive of this air; 

 and M. Fourcroy has difcovered, that the air bladders 

 of n"fhes, and particularly of the carp, are full of it ; 

 and that it may be collected by breaking them under 

 glafs vefTels inverted in water. The air, however, 

 which is contained in the bladders of marine plants, is 

 found to be confiderably purer than atmofpheric air. 



In fpeaking of the properties of this fluid it is necef- 

 fary to remark, ift. That azotic gas affords no fign of 

 acidity, not being capable of turning the blue colours 

 of vegetables red *. 



2d. It does not precipitate lime diffolved in water; 

 for if a fmall quantity of lime-water is put into a tube 

 filled with this gas, it will remain clear and limpid ; 

 there will be neither lime precipitated nor chalk formed, 

 which evinces that it is radically different from fixed 

 or carbonic acid air. 



jdly. Another property of this gas is that of fuddenly 

 extinguiming fubftances on fire, and not fuftaining the 

 vital principle in animals which arc plunged into itf. 

 This may be proved by introducing an animal or a 

 burning candle, into a veffel full of this gas ; the animal 

 will be fuddenly fuffocated, and the candle inilantly 

 extinguifhed. 



* The common teft of che mills, to prove whether any flu54 con- 

 tains an acid. They ccrnmonly drop a fmall portion of the fluid 

 into a clear phial containing fyrup of violets ; but the rhofl delicate 

 teft is, a paper ftained with tinclure of Uirjifole or litmus, to which 

 the acid is applied by a feather. 



f Animal life, however, does not appear to be deftroyed by any 

 noxious quality in this air, as is the cafe in breathing fixed air; 

 but the animal dies for want of the necelfory pabulum of oxygen 

 gas. 



4 thly. 



