VOL. LXXVlJ PHILOSOPHICAL TRANSACTIONS. 7I 



Mr. K. attempted to extract air from a mixture of oil of olives with caustic 

 vegetable alkali. It immediately whitenedj and on applying heat effervesced so 

 violently as to pass over into the receiver: nor had he better success on adding 

 an acid. The event was different when on a few grains of sulphur he poured 

 some of the oil, and heated them in a phial with a bent tube; for as soon as the 

 sulphur melted, the oil began to act on it, got red, and emitted hepatic air, 

 similar to that produced by other processes. He also obtained this air in great 

 plenty from a mixture of equal parts sulphur and pulverized charcoal, out of 

 which its adventitious air had been as much as possible expelled by keeping it a 

 long time heated to redness, in a crucible on which a cover was luted, with a 

 small perforation to permit the air to escape. This air was inflammable, as ap- 

 peared by holding a lighted candle before it during its emission; yet it is hardly 

 possible to free charcoal wholly from foreign air, for it soon re-attracts it when 

 exposed to the atmosphere. This last mixture, when distilled, affording a large 

 quantity of hepatic and some inflammable air. 



Six grs. of pyrophorus, made of alum and sugar, effervesced with marine 

 acid, and afforded 2.5 cubic inches of hepatic air. This pyrophorus had been 

 made 6 years before, and was kept in a tube hermetically sealed, and for many 

 summers exposed to the strongest light of the sun. It was so combustible, that 

 some grains of it took fire while it was introduced into the phial out of which 

 the hepatic air was expelled. A mixture of 2 parts white sugar (previously melted 

 in order to free it from water) with I part sulphur, when heated to about 6oo or 

 700 degrees, gave out hepatic air very rapidly. This air had a smell much re- 

 sembling that of onions; it contained no fixed air, nor saccharine, or other 

 acid. But sugar and sulphur, melted together, gave out no hepatic air when 

 treated with acids. Water, spirit of wine, and marine acid, decompose this 

 mixture, dissolving the sugar^ and leaving the sulphur. A mixture of sulphur 

 and plumbago afforded no hepatic air. 



On the General Characters of Hepatic Air. — Mr. K. found the absolute 

 weight of this air by weighing it in a glass bottle, previously exhausted by 

 Mr. Hurter's new improved air-pump, whose effect is so considerable as to leave 

 in general only -g-i-g- and frequently but -rVo-r part of unexhausted air. This 

 bottle contained nearly ll6 cubic inches; and this quantity of hepatic air 

 weighed 38.58 grains, the thermometer being then ^7^.5, the barometer 29.94, 

 andM. Saussure's hygrometer 84°, the weight of 1 16 cubic inches of atmospheric 

 air being at the same time 34.87 grs; hence a cubic foot of hepatic air weighs, in 

 these circumstances, 574.7O89 grains, and 100 cubic inches of it weigh about 

 33 grains: and its weight, relatively to that of common air, is as lOOOO to 

 9038.* This hepatic air was extracted from artificial pyrites by marine acid. 



• Hence the weight, says Mr. K., which I have assigned to common air in my first paper, after 



