VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. 6Q 



subject had occasioned. There is also great reason to think that it is the peculiar 

 product of the putrefaction of many, if not all, animal substances. Rotten 

 eggs and corrupt water are known to emit the smell peculiar to this species of 

 air, and also to discolour metallic substances in the same manner. M. Viellard 

 has lately discovered several other indications of this air in putrefied blood. 



Yet, deserving as this substance appears to be of a thorough investigation, it 

 has as yet been very little attended to. The experiments of M. Bergman have 

 not been sufficiently numerous, and thence he has been led into some mistakes. 

 Dr. Priestley has entirely overlooked it. The researches of the ingenious Mr. 

 Sennebier, of Geneva, have indeed been very extensive ; but as, for particular 

 reasons, he operated on this air over water, by which it is in great measure ab- 

 sorbed, instead of quicksilver, his conclusions appear in many respects objec- 

 tionable. The experiments now laid before the Society were all made over 

 quicksilver, and several times repeated. 



Of the Substances that yield hepatic air, and the means of obtaining it. — It is 

 well known, that saline liver of sulphur is formed, in the dry way, of a mixture 

 of equal parts of vegetable or mineral alkali and flowers of sulphur, melted 

 together by a moderate heat, in a covered crucible. When this mixture vi^as 

 slightly heated, it emitted a bluish smoke, which gradually became whiter as 

 the heat was increased, and at last, when the mixture was perfectly melted, and 

 the bottom of the crucible slightly red, became perfectly white and inflammable. 

 To examine the nature of this smoke, Mr. K. made a pretty pure fixed alkali, 

 by deflagrating equal parts of cream of tartar and nitre in a red-hot crucible in 

 the usual way; and mixing this salt perfectly dry with flowers of sulphur in 

 much smaller quantity, he gradually heated the mixture in a small coated glass 

 retort, and received the air proceeding from it over quicksilver. The first por- 

 tion of air that passed with a very gentle heat, was that of the retort itself, 

 slightly phlogisticated. It amounted to 1 .5 cubic inches, and with Dr. Priest- 

 ley's nitrous test, (that is, an equal measure of nitrous air) its goodness was 

 1.29. It contained no fixed air. The 2d portion of air obtained by increasing 

 the heat amounted to about 18 cubic inches. It was of a reddish colour, and 

 seemed a mixture of nitrous and common air. It slightly acted on the mercury. 

 The 3d portion consisted of 20 cubic inches, and appeared to be of the same 

 kind, but mixed with a little fixed air. This was succeeded by 64 cubic 

 inches of almost perfectly pure fixed air; and the bottom of the retort being 

 now red, some sulphur sublimed in its neck. When all was cold, liver of sul- 

 phur was found in the bulb of the retort. 



Hence we see that the blue smoke consists chiefly of fixed air, and the white 

 or yellow smoke of sulphur sublimed; and that no hepatic air is thus formed; 

 nor vitriolic air, unless the retort be so large as to contain a sufficiency of com- 



